Avocado production in Florida /

Material Information

Avocado production in Florida /
Series Title:
Bulletin / University of Florida. Agricultural Experiment Station ;
Wolfe, Herbert S ( Herbert Snow )
Toy, L. R
Stahl, Arthur L
Place of Publication:
Gainesville, Fla
University of Florida Agricultural Experiment Station
Publication Date:
Physical Description:
96 p. : ill., charts ; 23 cm.


Subjects / Keywords:
Avocado -- Florida ( lcsh )
bibliography ( marcgt )
non-fiction ( marcgt )


Includes bibliographical references (p. 95-96).
General Note:
Cover title.
Statement of Responsibility:
by H.S. Wolfe, L.R. Toy, Arthur L. Stahl.

Record Information

Source Institution:
Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location:
Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
18207194 ( OCLC )
027144336 ( Aleph )
S30.5 .S73 ( lcc )

Full Text


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

Bulletin 272 October, 1934

Wilmon Newell, Director




Fig. 1.-Linda avocado tree, typical of the low-headed varieties.

Bulletins will be sent free to Florida residents upon application to

John J. Tigert, M.A., LL.D., President of the Geo. H. Baldwin, Chairman, Jacksonville
University A. H. Blanding, Bartow
Wilmon Newell, D.Sc., Director A. H. Wagg, West Palm Beach
H. Harold Hume, M.S., Asst. Dir., Research Oliver J. Semmes, Pensacola
Haroli Mowry, M.S.A., Asst. Dir., Adm. Harry C. Duncan, Tavares
J. Francis Cooper, M.S.A., Editor J. T. Diamond, Secretary, Tallahassee
R. M. Fulghum, B.S.A., Assistant Editor
Jefferson Thomas, Assistant Editor
Ida Keeling Cresap, Librarian BRANCH STATIONS
Ruby Newhall, Administrative Manager
KI H. Graham, Business Manager
Rachel MeQuarrie, Accountant NORTH FLORIDA STATION, QUINCY
L. O. Gratz, Ph.D., Plant Pathologist in
MAIN STATION, GAINESVILLE R. R. Kincaid, Ph.D., Asso. Plant Pathologist
J. D. Warner, M.S., Agronomist
AGRONOMY R. M. Crown, B.S.A., Asst. Agronomist
W. E. Stokes, M.S., Agronomist** Jesse Reeves, Farm Superintendent
W. A. Leukel, Ph.D., Agronomist
Fred H. Hull, M.S., Associate John H. Jefferies, Superintendent
W. A. Carver, Ph.D Associate Ge. D. Ruehle, Ph.D., Associate Plant
John P. Camp, M.S., Assistant Pathologist
W. A. Kuntz, A.M., Assoc. Plant Pathologist
ANIMAL HUSBANDRY B. R. Fudge, Ph.D., Associate Chemist
A. L. Shealy, D.V.M., Animal Husbandman* W. L. Thompson, B.S., Asst Entomologist
R. B. Becker, Ph.D., Dairy Husbandman
W. M. Neal, Ph.D., Associate in Animal EVERGLADES STATION, BELLE GLADE
Nutrition A. Daane, Ph.D., Agronomist in Charge
D. A. Sanders, D.V.M., Veterinarian R.N. Lobdell, M.S., Entomologist
ML W. Emmel, D.V.M., Asst. Veterinarian F. D. Stevens, B.S., Sugarcane Agronomist
W. W. Henley, B.S.A., Asst. Animal Hus- G. R. Townsend, Ph.D., Asst. Plant Patholo-
bandman gist
P. T. Dix Arnold, B.S.A., Assistant Dairy B. A. Bourne, Ph.D., Sugarcane Physiologist
Husbandman J. R. Neller, Ph.D., Biochemist
R. W. Kidder, B.S., Asst. Animal Husband-
R. W. Ruprecht, Ph.D., Chemist** Ross E. Robertson, B.S., Assistant Chemist
R. M. Barnette, Ph.D., Chemist
H. W. Winsor, B.S.A., Assistant H. S. Wolfe, Ph.D., Horticulturist in Charge
H. W. Jones, M.S., Assistant W. M. Fifield, M.S., Aset. Horticulturist
Stacy 0. Hawkins, M.A., Assistant Plant
C. V. Noble, Ph.D., Agricultural Economist**
Zach Savage, M.B.A., Associate BROOKSVILLE
A. H. Spurlok, M.S.A., Assistant W. F. Ward, M..A., Asst. Animal Husband-
ECONOMICS, HOME man in Charge*
Ouida Davis Abbott, Ph.D., Specialist**
L. W. Gaddum, Ph.D., Biochemist FIELD STATIONS
C. F. Ahmann, Ph.D., Physiologist
J. T. Hall, Jr., B.S.Ch.E., Asst. Physiologist Leesburg
ENTOMOLOGY M. N. Walker, Ph.D., Plant Pathologist in
J. R. Watson, A.M., Entomologist** W. B. Shippy, Ph.D., Asso. Plant Pathologist
A. N. Tissot, Ph.D., Associate K. W. Loucks, M.S., Asst. Plant Pathologist
H. E. Bratley, M.S.A., Assistant J. W. Wilson, Ph.D., Associate Entomologist
J. W. Kea, B.S.A., Assistant C. C. Goff, M.S., Assistant Entomologist
A. F. Camp, Ph.D., Horticulturist** A. N. Brooks, Ph.D., Plant Pathologist
G. H. Blackmon, M.S.A., Horticulturist R. E. Nolen, M.S.A., Asst. Plant Pathologist
A. L. Stahl, Ph.D., Associate Cocoa
F. S. Jamison, Ph.D., Truck Horticulturist
R. J. Wilmot. M.S.A., Specialist, Fumigation A S. Rhoads, Ph.D., Plant Pathologist
Research Hastings
R. D. Dickey, B.S.A., Assistant Horticulturist A. H. Eddins, Ph.D., Plant Pathologist
W. B. Tisdale, Ph.D., Plant Pathologist** G. B. Fairchild, M.S., Assistant Entomologist
George F. Weber, Ph.D., Plant Pathologist
R. K. Voorhees, M.S., Assistant Bradenton
Erdman West, M.S., Mycologist David G. Kelbert, Asst. Plant Pathologist
Lillian E. Arnold, M.S., Assistant Botanist
In cooperation with U.S.D.A. E. R. Purvis, Ph.D., Assistant Chemist,
** Head of Department. Celery Investigations


Introduction ...... .... .. ..-.... .----. ..- ..-- .---..--.. --. ...- .......--- 5
H history ....................................... ..... ........................... .... .... 6
Distribution in Florida ......-....-....--...................... ------ -- ---.....-.--- 8
Distribution Factors -..... .-..-..-..-............ .....-....... 8
Distribution by Counties ..................- -.--.. -- ---- ............ ...... .... 10
Distribution by Varieties ......... ---...-....--....-----..-------..-..--------. 11
Uses of the Avocado ..................................----- ------- ............ .. ... 14
Botany of the Avocado -----------------.....--------- --....-.--------------- 16
Description of Species- .............. --..... ....-..-.-...- ----- -------- 16
Relationships ..................... ~. .......- ------ -----------------------. .... .. 18
Races ......... --......... ----...... .... -------............ ---------------------------................ 18
Varieties Cultivated in Florida .... -.................. .......... ............ .......... .... 19
W est Indian Race ............ ............................-----.................................... 21
GuatemalankRace---- --------------------------------------------------------------------------- _26
Guatemalan Race ............................................. ..-.......--------------- .. .. 26
H ybridsc ... .................................... ......... ........ ................- ........... ....... ...................... 82
Pollination and Interplanting ..................................................6.... ........ .... ......- S6
Flower Behavior .........-...........-......-. --. ----------.-- ........... .. ... 36
H and Pollination ....................................--..--....----- ........... -...................-...... 42
Insects and Pollination ....---.. ..-.........---..--.......- ...--.............-.......--- ----...--- 42
Interplanting Observations ...-........--...--- .....-.-.................. .......... ..................-.-- 43
Analyses of Avocados .-.. ..-.... -....-.............. ....... ...................... 46
Propagation .................... .............. ....--. ...... ............... ...... 53
Nursery Practice ...............................
Rootstocks .............-..... ...----.---.-............... ......... ----...---- 58
Top-working .....-..... .-.....- .....- ................ ... ........... ..... .... 59
Grove Management .................................... --. ....------ 64
Planting Distances ........... .... ............... ......... ........ ......... ..... 64
Preparation of Land ............................ --...-....--. ----.. ---- ................ .. 65
Time of Planting ......... ................................... ............................- 66
Interplanting Recommendations ............................................................... .............. 67
Planting .... .------.............................. --. ........-- .......------- --.-- .... ......... .. 72
Cultivation and Mulching .-....... + -.....--....-- .--......................----- 74
Cover Crops ..........-..............--... --.. .......... ............... 75
Pruning ...................... -- -------- ............ ...... ................ 76
Fertilization ...... --------- .........................---.76... ........... ..... .......... 76
W indbreaks ............-......................... -- .-- .- .....-----....... .....- ................ 78
Rejuvenation of Neglected Crops .............................................--... 80
The Crop ................................. ...... .. ..... ... .............. .. ..... ...... .. ...... 81
Yields ... ............................................. ........ ....... .............. .... ... 81
Thinning ..................................... ...................... ..... ........ ........ .. 81
Picking ...................... .... .............................-................. .................... 82
Packing ................................................ ..................... 84
M marketing ........................................ ........ .... ...-- ----- ....... ........ ..................... 85
D diseases ................................................. ......... ..... ........................ 86
Anthraenose (Black Spot) ...--- ........ .......... ............. ..................... 86
Blotch .......-.-.....--....-- .----------------------------------------------- .................... .... 86
Scab ..................................... ...... ........ .............. ....... .. .. .... .................. ... 87
Minor -iseases----------- *---------------------------------------------------- 81
M inor D diseases ....................................................................................... 87
Physiological Diseases ...... ........................................................................ 88
Insects and Other Pests ............................................. .. ........................... ... .. 88
Dictyospermum Scale ..................... .- ................................................... 89
Pyriform Scale ..+............ ... ............................................. 90
Avocado W hite-Fly ........... ................. ---------------.. ......... ........................ 90
Avocado Red Spider ...... ......................................................... 90
Avocado Lace-Bug .................... ................... ................................................... 91
Avocado Leaf-Roller ......... ........................................ ....... .................................... 91
Blossom A nom ala ............................ ................................................ .... 92
Blossom Thrips ..........------------ .. ........... ..........-----------........................ 92
Leaf-Infesting Thrips ................. ...................... ................................................. 92
Tentw orm ................................. ... ..... ...........--. ................-....... 93
Borers ........................................ ................. ... ..... ........ ............... ........... ......... .. 9
M inor Insect Pests ........ ...... ..... ................................ ............ ............. 94
R odents .............................. ... ..................------ ..... ..................... ..... ..... 94
L literature C ited .. ................. .. .. ....... ......... .......... ............................................ 95


Fig. 2.-Trapp avocado tree, typical of the large, spreading varieties.

By H. S. WOLFE, L. R. TOY* and A. L. STAHL

The most distinctive horticultural industry of the southern
half of Florida is the growing of avocados. Nowhere else in the
United States, except in southern California, can avocados be
produced as a commercial proposition, and the Florida industry
is much older than the California one. In Dade County avocados
have been of increasing commercial importance for over 35
years, while in other parts of the state avocados have been
grown for shorter periods of time. In spite of the many years
of commercial culture, there is still a great deal to be learned
about the avocado and its requirements. Though numerous
seedlings have been named and propagated as varieties, there
is still no general agreement as to satisfactory varieties for
The avocado has been for centuries the great food crop of
Central America and adjacent territory, where it is indigenous.
Hitherto it has been considered a luxury crop in the United
States, and only a very small percentage of the population is
acquainted with it. The day of phenomenal prices for avocados
as rare exotic fruits has passed. Instead of thinking of prices
of a dollar or more apiece, the grower must think in terms of
5, 10 and 15 cents per pound. Sooner or later the avocado will
take its place as a real food crop in this country.
The consumption of avocados is already quite large, consider-
ing the small number of consumers familiar with it. From
10,000,000 to 20,000,000 pounds are consumed annually in this
country. Of this amount, Florida produces about 15 percent,
California about 25 percent, and Cuba the remaining 60 percent.
Since the California crop is mostly marketed during the winter
and spring, while the Cuban crop is marketed during the same
season as the Florida crop, summer and fall, the tremendous
importation of Cuban seedling fruit is the most serious obstacle
which the Florida grower has faced in his progress toward
prosperity. Increasingly, the Florida avocado grower has turned
his attention to varieties which mature in late fall and winter.
In view of these considerations, it is increasingly important
for the Florida avocado grower to make every tree produce its
utmost. Unproductive varieties, and unproductive trees within
Formerly Assistant Horticulturist, Sub-Tropical Experiment Station.

6 Florida Agricultural Experiment Station

the variety, must be eliminated from the grove. Production
costs must be reduced to the minimum. The grower must con-
centrate on the production of quality fruit, and this must include
full consideration for the appeal which the fruit makes to the
consumer. No finer quality avocados are produced anywhere
than in Florida, if they are allowed to mature properly before
they are picked.
Many of the problems of avocado culture which confront the
grower are under intensive investigation at the Sub-Tropical
Experiment Station. Chemical analyses of avocado fruit have
been carried out over several years at the Main Agricultural
Experiment Station in Gainesville.
In the preparation of this bulletin, invaluable assistance has
been received from many individual growers, whose years of
practical experience have been drawn on freely. County agents,
nurseries and the Florida Avocado Growers' Exchange all have
assisted in making the data contained herein as complete and
accurate as possible. The Bureau of Plant Quarantine of the
U. S. Department of Agriculture has kindly made accessible
the tree records of the census made during the campaign against
the Mediterranean fruit fly. Most of the photographs were
taken by Dr. A. F. Camp and Mr. Harold Mowry, of the staff
of the Experiment Station. The photograph from which Fig. 7
was taken was kindly loaned by the U. S. D. A. Plant Introduc-
tion Garden at Miami. Dr. W. B. Tisdale and J. R. Watson
read the sections on diseases and insects, and very kindly gave
their advice on these subjects.

The avocado, like corn and tobacco, was unknown to the Euro-
pean world until after Columbus made his voyages. Research
into the literature by Popehoe (15) shows that the earliest
written record of the avocado is found in an account by Martin
Fernandez de Encisco, in his "Suma de Geografia", published in
1519. In speaking of the fruits of Columbia, he mentions "one
which looks like an orange and when ready for eating becomes
yellow; the inside is like butter and of marvelous flavor.". A
few years later Gonzalo Hernandez de Oviedo, who also saw it
in Columbia, wrote of it as a "pear", but was careful to state
That it was a pear in shape only. The fruit had been used for
Figures in parentheses (Italic) refer to "Literature Cited" in the back
of this bulletin.

Avocado Production in Florida 7

a very long time by the Indians of Central America and adjacent
portions of North and South America before the Spaniards
came, and an account written in 1653 by Bernardo Cobo, a priest
who had travelled widely in tropical America, seems to indicate
clearly that already at that time the three present horticultural
races were well differentiated.
The fruit was known to the Spanish conquistadores in Mexico
as "aguacate", and Salazar, writing in 1554, calls it by that
name. Under this name in its correct form, "ahuacate", it is
known in Mexico today, and this in turn is a variant of the an-
cient Aztec name "ahuacatl". No records have been found to
indicate how long it had been used by the pre-Colombian Indians.
The accepted present English name, avocado, is of course derived
from the Spanish variant of the old Aztec name. Sometimes it
is written "avocado-pear" and, more rarely, "alligator-pear",
while in the West Indies and southern Florida the fruit is com-
monly called "pear", since the true pear does not generally grow
in the same region. The correct name is avocado, and the mis-
nomer "pear" should be dropped as speedily as possible.
Undoubtedly the avocado was introduced into Cuba and
Jamaica by the Spaniards soon after the Conquest, and they
must also have introduced it into Florida not long after. Records
show the killing of "alligator pears" at St. Augustine in the
very cold winter of 1835, and these were undoubtedly West
Indian seedlings. The first recorded importation was by Henry
Perrine in 1833, and consisted of trees from Mexico for his grant
of land, now Dade and Monroe counties. It is not known whether
these were of the Mexican or Guatemalan race, and the fate of
the plantation is also unknown. When the first permanent set-
tlers came to the Miami region in the middle of the last century,
they found only the West Indian seedlings growing wild in the
hammocks. By 1900 there were several groves of West Indian
seedlings established near Miami for commercial production.
Late in the 1890's the first known successful budding of the
avocado was accomplished by a man named Smith living in
Coconut Grove, and in 1900 George B. Cellon began commercial
propagation in the first avocado nursery to be established. The
first imported budwood was of a Hawaiian variety imported by
A. A. Boggs in 1903, but until the U. S. D. A. began bringing
in Guatemalan seeds in 1906, all commercial propagation in
Florida was of selected West Indian seedlings of local origin.
The fruiting of some of these Guatemalan seedlings created much
interest in the possibility of extending greatly the season of

8 Florida Agricultural Experiment Station

fruiting in Florida, as these fruited during the spring months
when there had formerly been no avocados. In 1914 Wilson
Popenoe made selections of Guatemalan and Mexican varieties
in California and brought budwood back to Florida, and in the
same year O. F. Cook, also of the U. S. D. A., made the first
selections of budwood in Guatemala. Popenoe made extended
investigations of the avocado in Guatemala in 1916 and 1917,
sending in budwood of many selected trees, and in 1921 he did
the same in Ecuador. There have been no further importations.
The Franciscan friars do not seem to have brought avocados
with them from Mexico when they established themselves in
California in the early part of the 18th century, although they
brought the orange, grape, fig and olive. All of these, however,
had been brought originally from Europe. The first introduc-
tion of the avocado into California is stated by Condit (4) to
have been sometime prior to 1856, when an avocado from Nica-
ragua was growing near San Gabriel. In 1871 avocados were
introduced as seedlings from Mexico to Santa Barbara, and in
1880 Guatemalan seeds were planted in Los Angeles. The first
grove planting, all of Mexican seedlings, was made in 1885 at
Santa Barbara. During the 1890's Juan Murietta and later
C. P. Taft made many introductions of Guatemalan seeds from
Mexico, and the fruiting of these seedlings created the first ex-
tended interest in avocados in California. In 1911 a commercial
nursery, the West India Gardens, sent an explorer to make
selections from old plantations in Mexico, and the first budwood
was sent in by him. As already recorded, the U. S. D. A. under-
took avocado explorations a few years later, and E. E. Knight
imported his own selections also in 1914.
Hawaii received avocado seeds from Central America before
1825, chiefly of the West Indian race but also some Guatemalans.
Introductions into many other countries have come in recent
years, and now avocados are cultivated in Algeria, Australia, the
Canary Islands, southern France, Madagascar, Madeira, Mauri-
tius, New Zealand, Palestine, the Philippine Islands, Polynesia,
South Africa and southern Spain, as well as all over the West
Indies, Central America, Mexico and the northern half of South
Distribution Factors.-Of the various environmental factors
which limit the distribution of plants, temperature minimum is
the most important for the avocado. It is distinctly tropical

Avocado Production in Florida 9

and sub-tropical in its requirements, and so occupies a narrowly
limited range in this country. Mature trees of the West Indian
race are killed by temperatures of 240 F. and injured considera-
bly at 270, while Guatemalan varieties are not killed above 210
and some very hardy Mexican varieties endure less than 200.
Young trees have temperature minima a few degrees higher
than mature trees, and those in their first year cannot endure
temperatures within six or seven degrees of what mature trees
can. The Mexican varieties are the hardiest, and have a distri-
bution like that of the orange. The West Indian varieties are
tenderest, and have a temperature distribution similar to that
of the lime, while the Guatemalan varieties are rather intermedi-
ate in cold endurance, and may be compared to the lemon. Where
the temperature is known to fall below the minimum endured by
the variety, it is unwise to plant avocados of that race, although
they may grow and fruit well for several years before a cold
winter freezes them back.
Because of their sensitivity to cold, it is especially important
that adequate air drainage be provided for avocados, particularly
in the Ridge section of the state. Only the best situated land
is suitable for avocado culture, preferably a hillside with a lake
at the bottom. In southern Florida, where most of the .vncd.rna
are grown, this factor of air drainage plays a minor role, both
because of the very slight contours of the terrain and because
of higher average temperatures.
The avocado is very catholic in respect to soils, being appar-
ently equally at home on the limerock of the Redlands, the sand
hills of the Ridge, and the muck of the Lake region. It is very
intolerant, however, of standing water, and cannot endure "wet
feet" for more than a day or two at most. Consequently, care
must be taken to set the trees high in the low portions of a grove,
and to avoid planting in areas subject to standing water during
the season of heavy rains. Where citrus trees endure a week
or two of overflow, the avocado is killed within a couple of days.
Like most other fruits, the avocado does not thrive where
exposed to strong winds. It is both possible and desirable to
plant a line or belt of trees as a windbreak, in places where
there is no natural protection from the winds, and so this factor
can hardly be considered as limiting avocado culture. The ex-
treme brittleness of the wood of the avocado is a sound reason
for the advisability of giving plantings windbreak protection,
but reduction of evaporation loss during the dry seasons, and

10 Florida Agricultural Experiment Station

prevention of bruising of fruit by wind movements are even
more important factors.
Nowhere in Florida is rainfall a limiting factor, unless per-
haps on some of the Keys. Trees growing at Key West usually
have an unhealthy appearance, but this is more probably due
to leaf burn by the salt spray than to water deficit. The fruit
is not hurt by rains during ripening, and the flowering period
is sufficiently extended so that the occasional rains at that
season do not usually affect adversely the setting of fruit.
(Data as of Jan. 1, 1933)
Number of Avocado Trees
County Bearing I Non-Bearing I Total
Broward ................................ .................... 5,000
Charlotte .......................... ....................... 600
Collier .........-...........----- -. ........... ............ 1,000
Dade ...................................... 80,000 30,000 110,000
Glades .......... ............... ........... ...... ... 50
H endry .............................. .. .......................... 150
Highlands .................. ............ ........... 7,000
Hillsborough ...................... ......... -........... 2,500
Lee ........................................ ............ ...... .... 5,000
M anatee ............................... ............ ........... 4,300
Martin .................................. 3,100 7,500 10,600
Orange ............... ............... ........... ........... 1,000
Palm Beach .......................... 18,000 5,000 23,000
Pasco .............................. .. ........... ............ 100
Pinellas ...................... ..... ............ ............ 5,400
Polk .......-----------------.. ............ ........... ........... 1,000

Totals .............................. 134,200 42,500 176,700

Distribution by Counties.-In Table 1 is shown the distribu-
tion of avocado trees by counties in Florida, so far as it has been
possible to ascertain this. The total number of avocado trees
in the state is about 175,000 and of these about 15,000 are in

Avocado Production in Florida 11

dooryard plantings of a few trees each. The bulk of the trees
are set in grove form, and comprise about 2,000 acres in plant-
ings ranging from less than one acre to over 100 acres in size.
Nearly two-thirds of the total grove acreage is to be found in
southern Dade County, where the climate is most suited to the
avocado of any portion of the state. There are a number of large
groves in Highlands County and still more in Palm Beach County
around the southeastern shore of Lake Okeechobee. There have
been repeated attempts during the last 30 years to establish
large groves in this latter region, where the growth of the trees
is phenomenal, but all of the plantings now found there are less
than six years old, as frost and flood have wiped out the older
ones. Until water control is more assured, plantings there must
continue to be hazardous ventures, but some day there may be
a large development around the lake. The Ridge section has
many excellent avocado sites still available, where air drainage
offers cold protection, and the Redlands section in southern Dade
County has thousands of acres of potential avocado land.
Although there are occasional groves of a few acres' size
scattered through the remaining counties, the bulk of the trees
in them is in dooryard plantings, especially in Tampa, Fort
Myers, Clearwater and other cities. There are also scattering
single trees, particularly of the hardy Mexican race, in nearly
every county in the peninsula, even as far north as St. Augustine
and Gainesville.
The East Coast counties have about 147,000 trees, the West
Coast counties 19,000, and the Central counties about 9,000, in
round numbers. Of the total 175,000 trees, probably 10 percent
are seedlings and the other 90 percent are budded or grafted to
some named variety. About one-fourth of all these budded trees
are not yet in bearing and another fourth will not be in full pro-
duction for two or three years. These figures are interesting
for comparison with those for California, which now has about
12,000 acres with 60 percent of them bearing, or about 1,000,000
trees with 600,000 in bearing, of which half are not yet in full
Distribution by Varieties.-It is not possible to make a com-
plete enumeration of all the bearing groves in the state, let alone
one that will include all the small home plantings. There has
been made, however, a census of the greater part of the com-
mercial groves in Dade County, and this is presented in Table 2.
Some 84,000 trees are accounted for, which includes 75 percent

12 Florida Agricultural Experiment Station

of all the avocado trees in Dade County and nearly half of all
the trees in the state.

Total Percent of Total Percent of Total
Varieties Trees I Trees Production

Collinson ....................... 16,660 19.8 6.0
Fuchsia .......................... 2,435 2.9 0.25
Lula ................................ 6,700 8.0 3.0
Peterson ........................ 140 0.16 0.25
Pinelli .............................. 525 0.6 2.4
Simmonds ...................... 1,165 1.4 1.0
Taft .................................. 2,400 2.9 0.1
Taylor .............................. 3,450 4.1 6.0
Wagner ............................ 3,800 4.5 6.0
Waldin ............................ 11,825 14.1 23.0

Total "A" Varieties...... 49.100 58.5 48.0

Booth, 3, 7 and 8............ 380 0.45 0.1
Eagle Rock .................... 320 0.4 ..........
Itzamna .......................... 200 0.25 0.1
Linda ................................ 4,700 5.6 4.3
McDonald .......------......... 100 0.1 0.1
Pollock ............................ 6,000 7.1 6.0
Schmidt .......................... 1,100 1.3 0.4
Trapp ...--........................... 7,400 8.8 27.0
Winslowson .................... 9,200 11.0 7.0

Total "B" Varieties...... 29,400 35.0 45.0

Seedlings and Misc....... 5,500 6.5 7.0

Totals ........................... 84,000 100.0 100.0

Avocado Production in Florida 13

It will be seen that nearly 20 percent of the trees in these
groves are of the Collinson variety, with Waldin (14 percent)
ranking second. These two varieties make up over one-third
of all avocados in the county at present. Winslowson, Trapp,
Lula and Pollock make up another third of the total. For many
years the Trapp dominated avocado plantings, but with the
extensive development of the industry in the last 10 years other
varieties have predominated. It is also interesting to observe
how many of the unfortunately planted Taft variety still remain
to be worked to some profitable variety.
There are also given in this same table the production figures
by varieties, for comparison with the number of trees. These
figures represent the average production for the three seasons
1931-32, 1932-33, and 1933-34, and are taken from the records
of the Florida Avocado Growers' Exchange. The production
thus represented is not the crop from all of the trees included
in the count, but it does represent the product of at least half
of them, and it is believed to be reliable for purposes of com-
The most striking feature of the production figures is the low
proportion of the total yield which is borne by Collinson and
Lula, in comparison with the high proportion borne by Trapp
and Waldin. Apart from the difference in the fruitfulness of
these varieties, it must be realized that the groves of Trapp,
and to a large extent of Waldin also, are made up of mature
trees, whereas the Collinson, Lula, Fuchsia and Simmonds plant-
ings are mostly not yet in full bearing. The percentage yields
for the different varieties will be quite different when these
varieties come into full production in a few years.
The varietal census probably will be changed considerably
when it is repeated in five or 10 years. Some varieties here given
will have been top-worked to more desirable varieties, while
some varieties not even named here will be represented in quan-
tity. The Florida avocado industry is still far from the condition
of the industry in California. There the Fuerte variety now
constitutes over 60 percent of all plantings, whereas in 1927 it
made up less than 30 percent and in 1924 only 10 percent of the
total. The Taft variety accounted for 24 percent of California
avocado trees in 1924, but makes up less than 5 percent now,
while the Puebla rose from 1 percent in 1924 to 14 percent in
1927 and now is less than 10 percent of the total. Florida plant-
ings are in a condition similar to that in California 10 years ago,

14 Florida Agricultural Experiment Station

but by reason of the necessity for a succession of varieties ma-
turing from June until March, there can probably never be any
one variety which holds the place in Florida that Fuerte now
holds in California.
In spite of the dominance of the Fuerte, there are a great
many more named varieties being grown in California than in
Florida, and a score of new varieties is offered each year for
registration. The need of constantly searching for new and
better varieties is even more imperative for Florida growers,
because Florida can show no variety as satisfactory, even for
its proper season, as the Fuerte has proven for California.

The avocado has achieved fame mostly as a salad fruit, and
as such is widely used all over the United States, but sight
should not be lost of the fact that it is a nourishing food also.
In its tropical home, it is one of the most important items of the
daily diet of the natives during its season of ripening. When
the production in this country passes the amount which can
be consumed as a luxury fruit, it may be necessary to consider
primarily the food value of the avocado. At present, however,
that is secondary.
As "the salad fruit from the tropics" and "the aristocrat of
fruits", the avocado is prized in salads for its delicate, nut-like
flavor and its smooth, buttery consistency. One of the most
popular ways of serving it in Florida is "on the half-shell", with
the addition of lime or lemon juice or of salt only. Because of
its oil content, it need not be served with an oil dressing. The
fruit is frequently made an ingredient in salads of the Waldorf
type, or mixed with grapefruit or orange.
The use in salads is by no means the only use made of avocados
in Florida, although California has been more active than Florida
in developing ways of using avocados. Mashed and seasoned,
they are used as a sandwich filling, or are spread on salted
crackers, and in the tropics they are often added to soups just
before serving. Fully ripe fruit has been utilized successfully
in the manufacture of avocado ice cream, and this offers some
promise as an outlet for the disposal of fruit unsalable by reason
of appearance but of good quality.
Cooking detracts from both the flavor and the appearance of
the avocado, and so it cannot be preserved by canning. Fruit
preserved by quick-freezing processes often retained good ap-

Avocado Production in Florida 15

pearance, but it has been tasteless. The extracted oil is suitable
for making soap and for other commercial uses, but it cannot
compete profitably with other vegetable oils of far cheaper pro-
duction. Cruess (5) and his coworkers in California have re-
ported that the ground pulp can be stored satisfactorily in glass
containers at 15 F. or lower, and in this form it can be dis-
tributed for use in making ice cream or for soda fountain and
lunch room use in sandwich-spreads and salads. The cost of
this procedure is. still prohibitive commercially, although volume
consumption would make great changes in this. As production
increases, it will become more and more necessary to take ad-
vantage of every possible by-product usage to maintain a satis-
factory price-level for fresh fruits.
The dietetic properties of the avocado are unusual, only the
olive being at all similar among fruits. Compared with the
dessert fruits, the avocado runs higher in ash and protein and
lower in sugars, besides being outstanding in fat content. There
is great variation in this latter, the fat content of the fresh pulp
ranging from 2 to 30 percent. The high caloric value of the
avocado, together with the very low carbohydrate content, ren-
ders it especially suited to diabetic cases.
The avocado fat has been found by Mattill (10) to be as
digestible as butter fat, although not at all similar in composi-
tion. Vitamins have been reported on by Weatherby and his
associates in California, who have confirmed Santos (19, 28) as
to the excellence of avocados as a source of vitamin B and have
further shown the vitamin A content to be high (29). They
reported (30) only traces of C, fair amounts of D and good
amounts of E to be present. It should be remembered that so
far these tests have been made only on the Fuerte variety, which
is the commercial standard in California, and that the vitamin A
content in particular is likely to vary with the fat content of the
The expressed oil of the avocado is very similar in its chemical
constitution to olive oil, and is adapted to similar uses. Its high
cost makes its use in soap manufacture impracticable, but in
the last few years there has developed a small commercial utiliza-
tion of avocado oil in cosmetic manufacture. This development
has so far been limited to California. While the outlet thus
afforded for utilization of cull avocados must always be a limited
one, nevertheless it is one more factor making for the prosperity
of the avocado industry.

16 Florida Agricultural Experiment Station

Description.-The avocado is an evergreen tree with moder-
ately large, broad, leathery leaves, which vary in size from a
few inches to more than a foot in length. The wood is hard, but
and quite brittle,
so that the tree
is easily injured
in storms. Seed-
ling trees are
usually large and
handsome, but the
budded varieties
of horticulture
range in form
from low and
spreading to tall
and slender (Figs.
1, 2 and 3). The
twigs are rela-
tively thick and
the leaves are
borne alternately
Fig. 3.-Taylor avocado tree, typical of the tall, upon them, some-
slender varieties. times tending to
be clustered at the tip. The shape of the leaves is in general
oval to lanceolate or elliptic, with the tips usually acute but
sometimes obtuse in a few varieties, and the base cuneate. The
margin is entire and the venation distinct. The young leaves
and twigs are often finely pubescent, but at maturity they are
always quite smooth except in one small group of varieties.
There is considerable varietal variation in the glossiness and
shade of green of the avocado leaves, with varieties of the
Guatemalan race tending to be much darker green than those
of the West Indian group. Both leaves and bark contain oil
glands and mucilage glands.
The flowers are small, from half an inch to an inch across
when fully open, and are of an inconspicuous greenish-yellow
color. They are produced in enormous numbers in large spread-
ing panicles from the tips of the branches, sometimes nearly
covering the whole tree with a mantle of bloom. As is so often
the case in Nature, there is a prodigal wastage of flowers, only

Avocado Production in Florida 17

a small fraction of a percent of them ever maturing into fruit.
The flowers are perfect, with calyx and corolla distinguishable
only by position (as in the lily) and usually referred to as outer
and inner perianth segments. There are 12 stamens, in four
series of whorls, placed in double rank in front of each of the
perianth segments. Nine of these stamens are perfect and
functional, but the fourth or innermost series of three, located
opposite the inner perianth segments, has the stamens reduced
to staminodia. The perfect stamens each have four pollen cham-
bers, which open by uplifted flaps. In the outer two series these
openings are turned toward the center of the flower, but in the
third series, opposite the outer perianth segments, the openings
are outwardly directed. The peculiar behavior of the stamens
will be discussed in the chapter on pollination. The staminodia
secrete nectar, as does also the double set of glands at the base
of each of the stamens of the third series.
The pistil consists of a single carpel, and the egg-shaped ovary
is surmounted by a slender style of equal length, bearing at its
summit a slightly expanded stigma. This stigma is constructed
as if the upper end of the style were slit open along one side
and turned inside out, and the stigmatic surface is continuous
with the lining of the stylar column down which the pollen tube
grows. All parts of the flower are more or less covered with
fine hairs, although there is some varietal specificity in the
degree of pubescence. The ovary contains a single pendant,
anatropous ovule with two integuments. The fruit is a berry,
and consists of a single large seed, a thick fleshy pulp, and a
skin of varying thickness and texture according to the variety.
The shape of the fruit is usually from pyriform to round, but
is sometimes cucumber or gourd-shaped. In weight the fruit
may be anywhere from a few ounces to a few pounds, depending
on the variety.
The pulp is the edible portion of the fruit, and when ripe it
is of the consistency of cool butter or ripe melon. This pulp
varies in color from almost white to golden-yellow, according to
variety. In the thin-skinned forms one can determine ripeness
by external pressure, but in the very thick-skinned varieties
this cannot be done. In such cases the "straw test" is useful.
Whei the fruit is nearly ripe, the stem is easily pulled out of
the fruit, and a straw or toothpick can easily be pushed through
this opening and down through the pulp to the seed, when the
fruit is ripe enough for eating. The pulp contains a considerable
amount of vegetable oil or fat, varying from 2 to 30 percent in

18 Florida Agricultural Experiment Station

different varieties. The matured seed has two parchment-like
coats and two large hemispherical cotyledons stored with nour-
ishment for the small embryo which they enclose. This embryo
is at the end of the seed farthest from the stem, but is directed
toward it. Usually the seeds are not considered palatable, but
goats are said to eat them, and in Porto Rico there have been
attempts to use the ground seeds like cottonseed meal for cattle
Relationships.-The avocado belongs to the genus Persea
Gaertn., of the Lauraceae or Laurel family. To this family
belong also the true laurel, with which victors in the ancient
Olympic games were crowned, the sassafras, the camphor and
the cinnamon trees. The avocado is Persea americana Miller
(P. gratissima Gaertn.), native to Central America and adjacent
portions of North and South America, and a close relative is the
coya, P. schiedeana, of Guatemala. Popenoe (16) reports having
found wild forms of the true avocado (P. americana) in Costa
Rica, Honduras and Mexico. The genus Persea includes also the
native red-bay, shore-bay and swamp-bay of southern Florida.
Races.-For horticultural purposes it is sufficiently accurate
and far more convenient to consider that there is only a single
species of avocado, with three well-marked races-West Indian,
Guatemalan and Mexican. But there are technical reasons for
separating the last of these races as a distinct botanical variety,
P. americana var. drymifolia Mez. Formerly this variety was
considered as a distinct species, but Popenoe (16) has found
that the wild prototype from the highlands of Costa Rica and
Honduras possesses both the anise odor in the leaves character-
istic of the Mexican race and the leathery skin of the West
Indian race, so that the supposed species distinction is no longer
valid. The three horticultural races are easily distinguished in
cultivated varieties, in accordance with the following key:
1. Leaves anise-scented when crushed; fruit small, with skin
rarely more than 1/32" thick .....................----------Mexican
1. Leaves not anise-scented; fruit large or else very thick-
skinned, always more than 1/32" thick............................(2)
2. Fruit summer and fall ripening; skin leathery, about 1/16"
thick.......................... .. ........... ... .... .......... W est Indian
2. Fruit winter and spring ripening; skin thick and woody,
from 1/16" to 1%" thick................ ................Guatemalan
This scheme of differentiation is becoming constantly less
useful because of the increasing number of hybrid varieties

Avocado Production in Florida 19

being cultivated. Since these combine characters of two races,
it is impossible to distinguish them by any racial key.
The West Indian race is native to the lowlands of Central and
South America, and was introduced into the West Indies by the
early Spaniards. The name "West Indian", however, is so firmly
fixed that it is not worth while trying to change to a more apt
designation, and the race has been very much at home all
through the West Indies. The trees of this race are the most
sensitive to cold of any of the avocado races. The skin of the
fruit is always smooth and leathery, and in green-skinned vari-
eties is always a yellowish-green rather than a dark green. The
seed is comparatively large and often loose in the cavity, the
seed coats are usually separated, and the cotyledons are rough
on the surface. The fruit stems are short.
The Guatemalan race is native to the highlands of Central
America, and was unknown in Florida until after 1900. Although
native to Ecuador, Nicaragua and Mexico also, most of the im-
portations of seeds and scions have been 'from Guatemala, and
hence the race name. The trees are much more cold resistant
than those of the West Indian race, and the newly flushed foliage
is more frequently reddish or bronze in color, instead of green.
The skin of the fruit is always thick and woody, and usually
decidedly rough. In green-fruited varieties, usually the green
is a dark shade. The seed usually is small and fits tightly in the
cavity, the seed coats adhere closely to each other and to the
seed, and the cotyledon surfaces are smooth. The fruit usually
is borne on long fruit-stems.
The Mexican race is native to the highlands of Mexico and
of the whole Andean cordillera as far as Chile. The leaves and
young fruit possess a characteristic odor of anise when crushed.
The fruit is smaller than that of either of the other two races,
rarely exceeding one pound, and, in most varieties, averaging
eight ounces. The skin is nearly always quite thin and smooth.
The seed is comparatively large, the seed coats are thin and
either separated or adhering to the cotyledons and the surface
of the cotyledons is smooth.

Of the many varieties that have been named and propagated
at some time during the past 30 years, only a few have continued
in favor and are now found in commercial plantings. The present
section will describe chiefly only the varieties commercially

20 Florida Agricultural Experiment Station

planted in Florida. Many others have been planted, and some
are still being grown in a small way. The following varieties
are still fruiting in the state, but are mostly being top-worked
to more desirable varieties: Atlixco, Blakeman, Colla, Collins,
Dickinson, Knight, Lamat, McDonald, Mayapan, Nimlioh, North-
rop, Panchoy, Puebla, Queen, Solano, Spinks, Taft, Verde and
Winslow. There are also many promising new seedlings under
trial, but several seasons must elapse before they are sufficiently
tested to warrant extensive planting. A few of them are men-
tioned specifically at the close of this section.
Even after 30 years of commercial avocado culture in Florida,
there is no one variety or set of varieties which can be consid-
ered as wholly satisfactory. Each has some faults, and each
will be replaced eventually by a more desirable new variety. In
the Dade County area, a limited but representative survey of
growers made recently disclosed the following preference as to
varieties for commercial planting: Collinson ranked highest,
followed in order by Lula, Waldin, Trapp, Pollock, Taylor and
Schmidt. The preference indicated should not be considered as
conclusive, because of the limited extent of the survey and the
lack of familiarity on the part of the growers with some varieties,
but it is suggestive of trends. In the Ridge section the list of
preferred varieties is somewhat different. Lula, Collinson, Tay-
lor, Eagle Rock, Winslowson and Simmonds have proven satis-
factory for several localities.
The season of maturity of the fruit of any variety varies
somewhat with the locality, with the time of fruit setting, and
with the weather during fruit development. Consequently, only
an approximate season of maturity can be given. This variation
is not over two weeks, however, from one year to another, and
the approximate season of about eight weeks which is given
under each variety should include the variations.
The figures given under each variety for the fat content
indicate, wherever known, the normal average values for the
beginning and end of the given season of maturity. This fat
content is the value obtained by ether extraction of the fresh
pulp. Where there are no data as to seasonal range, the fat
content value is the average of a number of analyses of mature
fruits. The fat content for any given date may be higher or
lower by a small amount from one year to another, this variation
being about 2 percent for Guatemalan and hybrid varieties and
1 percent for the West Indian ones.
The pack indicated is that for the standard avocado lug.

Avocado Production in Florida 21


Fuchsia (Fuchs).-Originated on the place of C. T. Fuchs, Sr.,
Homestead, Florida, from a seed of unknown origin planted about
1910. Fruited first in 1916. Propagated commercially since
1926. Fruit pyriform to oblong, occasionally necked, of medium
size, 10-18 oz. Pack 14-20. Skin smooth, light green. Flesh
light greenish-yellow, of good flavor. Seed medium size, loose
in the large cavity. (Fat content 4 to 6 percent.) Season from
late June to early August. The variety is thrifty, prolific and
precocious, and is apparently the earliest maturing of the com-
mercial varieties now grown, but it has not been altogether
satisfactory in shipping behavior. Recommended for planting
in southern Florida.
Peterson.-Originated sometime prior to 1912 on the old Mur-
ray place, Silver Palm, near Homestead, Florida, as a seedling
of unknown origin. Budded trees from this seedling were given
Peter Peterson, of Modello, in 1917, and these he fruited first

22 Florida Agricultural Experiment Station

Fig. 5.-Fruit of the Peterson variety.

rut r

Fig. 6.-Fruit of the Pollock variety.

Avocado Production in Florida 23

in 1920. Propagated commercially in 1928. Fruit broadly oval
or top-shaped, of medium size, 14-20 oz. Pack 12-18. Skin
smooth, light glossy green. Flesh yellow, of very good flavor.
Fat content 4 to 7 percent. Seed medium size, often loose in
the cavity. Season September 15 to November 15. The fruit
has considerable resemblance to the Trapp, but is smaller and
more attractive, and has a smaller seed. Its habit of growth is
somewhat more thrifty also, but the fruit is subject to attack
by anthracnose. Recommended for planting in southern Florida.
Pollock.-Originated on the place of H. S. Pollock, Miami,
Florida, sometime prior to 1896, in a seedling plantation. Propa-
gated commercially in 1901. Fruit oblong to pyriform, very
large, 20-40 oz., or sometimes over 3 lbs. Pack 8-12. Skin
smooth, light glossy green. Flesh a rich yellow, blending with
green near the skin, of excellent quality. Seed large, often loose
in the cavity. Fat content 3 to 5 percent. Season July 15 to
September 1. For 25 years this was the leading early avocado
in Florida, but, although a vigorous grower, the tree is a shy
bearer. As the season of bloom is very early, it is possible that
injury to the bloom by low temperatures may sometimes be a
factor in its poor bearing. Although too large for general market

Fig. 7.-Fruit of the Simmonds variety.

24 Florida Agricultural Experiment Station

purposes, the fruit has usually commanded a good price because
of its fine quality and early season. It is no longer recommended
for commercial planting.
Simmonds.-Originated from seed of unknown origin sent to
Washington, D. C., from Miami in 1908. The seedling was sent
back to the U. S. Department of Agriculture Plant Introduction
Garden at Miami, and fruited there in 1913. Distributed by the
Garden without name in 1917, and named for the Superintendent
of the Garden, the late Edward Simmonds, in 1923. Propagated
commercially in 1921. Fruit oblong-oval to pyriform, large, 18-
34 oz. Pack 8-14. Skin smooth, light to yellowish green. Flesh
similar to that of Pollock, of very good flavor. Seed medium
size. Fat content 3 to 6 percent. Season July 15 to September
15. This variety has considerable resemblance to Pollock in
both vegetative and fruit characters, but is somewhat less vigor-
ous in growth and much more regular in bearing. Due to its
more dependable bearing and its smaller fruit size, it is replacing
Pollock somewhat. It is reported to shed a large portion of the
crop sometimes, however. Recommended for planting in southern
Florida and the Ridge section.

Fig. 8.-Fruit of the Trapp variety.

Trapp.-Originated on the place of H. A. Trapp, Coconut
Grove, Florida, about 1894, and fruited first in 1898. Propagated
commercially in 1901. Fruit roundish-ovate or slightly pyri-
form, medium to large size, 12-24 oz. Pack 10-20. Skin smooth,

Avocado Production in Florida 25

light to yellowish green. Flesh golden yellow, becoming pale
green next the skin, of excellent flavor. Seed large, often loose
in the cavity. Fat content 3 to 6 percent. Season September 1
to November 1. The tree is a comparatively weak grower, and
is rather susceptible to injury from insects and fungi. Some-
times it puts out such a tremendous quantity of bloom that it
suffers a set-back and carries little or no fruit to maturity. In
spite of these defects, the Trapp was the dominant variety in
Florida for more than 25 years. Originally it was popular be-
cause of its late season, it having been considered as a December-
maturing fruit, but its consistent bearing of good crops, its fine
shipping habit and the splendid quality of the fruit more than
offset its defects even after later maturing varieties came into

Fig. 9.-Fruit of the Waldin variety.

Waldin.-Originated on the place of B. A. Waldin, Homestead,
Florida, from a seed planted in 1909. Fruited first in 1913.
Propagated commercially in 1917. Fruit oblong to oval, with
a characteristic flattening of one side at the blossom end, medium
to large size, 14-28 oz. Pack 10-18. Skin smooth, pale green
to greenish yellow. Flesh pale to greenish-yellow, of good flavor.
Seed medium to large, fairly tight in the cavity. Fat content
6 to 10 percent. Season October 1 to December 1. The tree is
precocious, productive and hardier than most varieties of its
race. There is a marked tendency toward bearing the fruit in

26 Florida Agricultural Experiment Station

clusters, and such fruit is usually small and sunburned. Careful
attention to thinning should be given, to encourage normal fruit
development. In spite of the tendency to overbearing, and con-
sequent die-back of limbs, this variety has increased in popu-

Fig. 10.-Fruit of the Eagle Rock variety.

Eagle Rock.-Originated on the Galloupe place, Eagle Rock,
California, and called Galloupe in that state. Introduced into
Florida about 1920. Fruit roundish-oblate, large, 20-32 oz. Pack
10-16. Skin rough-pebbled, dark green. Flesh light to medium
yellow, of very good flavor. Seed medium large, tight. Fat
content 10 to 14 percent. Season January 1 to March 15. This
has been a very satisfactory variety in the Ridge section of
Florida, but has not proved satisfactory in Dade County. In
the latter area the trees are not vigorous and have generally
been light in bearing.
Itzamna.-Introduced as budwood from Guatemala by the U.
S. Department of Agriculture in 1916, this variety fruited first
at the Plant Introduction Garden in Miami in 1918. It was not
distributed until 1923 and has been commercially propagated
since then. Fruit oblong-pyriform with a slight offset of the
stem, medium large, 14-18 oz. Pack 14-18. Skin rough-pebbled,
dark green. Flesh yellow, of very good flavor, 11 percent fat

Avocado Production in Florida 27

Fig. 11.-Fruit of the Itzamna variety.

Fig. 12.-Fruit of the Linda variety.

28 Florida Agricultural Experiment Station

content. Seed small and tight. Season February 15 to April 15.
Although this variety has not yet been extensively planted in
Florida, it has been included in this list because of its good bear-
ing habits and very late season of maturity. Fruit often hangs
on the tree into May. It is the only one of the Popenoe intro-
ductions still planted in Florida. The variety deserves wider
planting, and is recommended for southern Florida.
Linda.-Introduced as budwood from Guatemala by E. E.
Knight, Yorba Linda, California, in 1914. Propagated commer-
cially in Florida in 1917. Fruit elliptical, very large, 20-40 oz.
Pack 8-12. Skin roughened, overcast with dull purple at ma-
turity. Flesh yellow, of excellent flavor. Seed small and tight.
Fat content 10 to 14 percent. Season December 15 to February
15. The tree is low and spreading in habit and is a good bearer,
with the fruit well distributed over the tree and protected from
injury by sun and wind. The fruit ships well, but on account
of its large size it is discriminated against in some markets.
This is the only one of the Knight introductions which has per-
sisted in Florida. It is not recommended for future planting
because of the large size and the color of the fruit.

Fig. 13.-Fruit of the Schmidt variety.

Avocado Production in Florida 29

Schmidt.-Introduced as budwood from Mexico by the West
India Gardens, Altadena, California, in 1911. Propagated com-
mercially in Florida in 1914. Fruit pyriform, medium to large
size, 16-26 oz. Pack 10-16. Skin rough-pebbled, dark green.
Flesh light yellow, of very good flavor. Seed medium size, tight.
Fat content 14 to 18 percent. Season February 15 to April 1.
This variety has generally proven a weak grower and poor bearer
in Florida. It is not recommended for planting.

Fig. 14.-Fruit of the Taylor variety.

Taylor.-Originated from a seed of the Royal planted at the
U. S. Department of Agriculture Plant Introduction Garden,
Miami, Florida, in 1908. Fruited first in 1913. Propagated
commercially in 1914. Fruit obovate to pyriform, rarely necked,
small to medium size, 12-18 oz. Pack 14-20. Skin rough-pebbled,
dark green. Flesh light yellow, of very good flavor. Seed medi-
um size, tight. Fat content 13 to 17 percent. Season December
15 to February 15. One of the first Guatemalan varieties to be
planted commercially, it is still popular. The tree comes into
bearing early, is vigorous in growth, and yields good crops well
distributed over the tree. The only objection is the tall, slender

30 Florida Agricultural Experiment Station

habit of the tree, which increases the time required for picking
and spraying. In spite of this defect, the variety is recommended
for planting in southern and central Florida.

Fig. 15.-Fruit of the Wagner variety.

Wagner.-Originated from a seed of the Royal planted on the
C. F. Wagner place, Hollywood, California, in 1908. Fruited first
in 1914. Propagated commercially in Florida in 1916. Fruit
rounded-obovate, small to medium size, 10-16 oz. Pack 14-24.
Skin slightly rough-pebbled, yellowish to dark green. Flesh
light yellow, of good flavor. Seed large, tight. Fat content 16
to 20 percent. Season January 15 to March 15. The tree has
many resemblances in foliage and fruit to its sister variety,
Taylor, but is distinguished from it by the lower growth habit
of the tree, the rounder fruit and larger seed, and the somewhat
later season of maturity. The tree grows thriftily and bears
well. The fruit is somewhat more subject to black-spot than is
Taylor. Recommended for southern Florida.

Up to the present there have been no large plantings of varie-
ties of this race in Florida. On the lower East Coast the West
Indian varieties are better adapted, and since the season of
ripening is the same, there has been no incentive to plant the
Mexicans. In the Ridge section, the Guatemalan and hybrid
varieties seem better adapted. Under the conditions in both

Avocado Production in Florida 31

these sections the fruit of the Mexican varieties shows a tendency
to uneven ripening of individual fruits and a considerable sus-
ceptibility to attack by anthracnose. In localities less favorably
situated with respect to cold, the Mexican varieties offer some
promise. Although the fruit is small in most varieties, there
are some in which the fruit is of fair size and good quality.
Small test plantings of several varieties should be made before
setting out an extensive acreage, in order to determine varietal
suitability. Little information can be given at present regard-
ing varieties suitable for planting in the colder parts of Florida.
Several have been fruited, but none can be recommended for
commercial planting as yet. The following seem the best for
trial in colder sections.
Gottfried.-Originated from a seed of a Mexican seedling on
the place of Edward Gottfried, Key Largo, Florida, planted at the
U. S. Department of Agriculture Plant Introduction Garden,
Miami, in 1906. Fruited first in 1914 and distributed in 1918.
Fruit pyriform, small to medium large, 10-20 oz. Skin smooth,
purplish-maroon. Flesh light yellow, of fair to good quality, 9
to 13 percent fat content. Seed medium size. Season June 15
to September 15. Quite frost resistant and a very vigorous
grower. On the lower East Coast it has proven an indifferent
bearer, and has been top-worked largely to better varieties of
the same season.
Puebla.-Introduced as budwood from Mexico by the West
India Gardens, Altadena, California, in 1911. Propagated com-
mercially in Florida in 1917. Fruit obovoid, small, 8-10 oz. Skin
smooth, deep maroon-purple at maturity. Flesh yellow, of very
good flavor, 12 to 15 percent fat content. Seed medium to large
size. Season September and October. One of the leading varie-
ties in California, but a poor shipper. It is thrifty and very cold
resistant. Not satisfactory in south-central Florida.
San Sebastian.-Another 1911 introduction by the West India
Gardens. Propagated in Florida in 1917. Fruit ovoid, medium
small, 12-16 oz. Skin rather thick, nearly black. Flesh yellow,
of fair to good flavor, 13 percent fat content. Seed medium size.
Season July and August. Very cold resistant variety but rather
poor bearer.
Duke.-Originated at Sunnyslope Nursery in California in
1912. Fruit pyriform, small, 8-12 oz. Season probably July and
August in Florida. It is not knoWn to have fruited in this state,
but is highly recommended in California for the cold sections,
and deserves trial in north-central Florida.

32 Florida Agricultural Experiment Station

While there is no commercial variety which has resulted from
a known cross, there are a number of varieties which give
evidence in their fruit and vegetative characters of being the
product of pollination of flowers of one race by pollen from
1. Guatemalan x West Indian hybrids originating in Florida
have attracted most attention. It has been noticed for many
years that where Guatemalan and West Indian varieties are
growing together, the seedlings from the former are likely to
exhibit the characters of both races, whereas the seedlings of
the latter have never been known to show any but West Indian
characters. In general the hybrids have shown what may be
considered "hybrid vigor", and have proven well adapted here.
In season of maturity and in fat content of fruit, these hybrids
are always nearer the Guatemalan than the West Indian parent,
but in general they fill in the gap in season between the two races.

Fig. 16.-Fruit of the Collinson variety.

Collinson.-Originated at the U. S. Department of Agriculture
Plant Introduction Garden, Miami, from a seed of the Collins
planted in 1915. Fruited first in 1920. Propagated commercially
in 1922. Fruit broadly obovoid to elliptical, large, 18-30 oz.
Pack 10-14. Skin leathery, smooth, dark green, usually glossy
but sometimes dull. Flesh creamy yellow, of very good flavor.

Avocado Production in Florida 33

Seed medium size, usually tight. Fat content 12 to 16 percent.
Season November 15 to February 1. This variety is exceptional
in being entirely unable to produce pollen and hence entirely
dependent on other varieties for pollination. The tree is a rapid,
vigorous grower, and the large, dark green leaves are resistant
to scab, as is also the fruit. The variety is fairly productive and
is almost as hardy as the Guatemalans. A deservedly popular
variety, recommended for every commercial avocado section in

Fig. 17.-Fruit of the Winslowson variety.

Winslowson (Rolfs).-Originated on the Rolfs place, Miami,
Florida, from a seed of the Winslow planted in 1911. Fruited
first in 1917. Propagated commercially in 1921. Fruit roundish-
oblate, large, 20-40 oz. Pack 8-12. Skin smooth, leathery, a dull
light green. Flesh pale yellow, of good flavor. Seed medium
size, often loose in the cavity. Fat content 9 to 15 percent.
Season October 1 to December 15. The tree is a rapid grower,
but, like the Trapp, it often suffers from over-blooming. Both
tree and fruit are subject to anthracnose attack. Dropping of
the entire crop of sound, fully-sized fruit within a period of a
few days has occurred in some years late in November. No
reason for this phenomenon has been apparent, and trees must
be watched closely at this period if the crop is to be saved.:
Shipments of this variety have been unsatisfactory in many
instances because of the tendency of the flesh to blacken around

34 Florida Agricultural Experiment Station 0

the seed when in cool storage. Because of the large size and
poor shipping quality of the fruit, and the frequent unthriftiness
of the tree, this variety is not recommended for commercial
New Hybrids.-Among the promising new seedlings are sev-
eral from seeds of various Guatemalans in a mixed planting
containing Trapps and Waldins. These have been fruited by
Will Booth, Homestead, Florida, and bear only numbers at pres-
ent. The most promising of these are Booth 8, maturing in
November, Booth 7, in December, and Booth 3, in January. An
unusually beautiful fruit, red-cheeked like an apple, is a seedling
of Collinred, the sister of Collinson, produced at the U. S. De-
partment of Agriculture Plant Introduction Garden at Miami.
It is called only Collinred B at present.
2. Guatemalan x Mexican hybrids have been very satisfac-
tory in California, but the only one that has proven generally
desirable for Florida has been one originating here, the Lula.
This is also the only one whose parentage is known even on one
side, the others being considered hybrids because of their being
too unlike the Mexican varieties for inclusion in that race, and
yet having some Mexican characters. As might be expected,
these hybrids are even more hardy to cold than most of the
Guatemalan varieties.
Fuerte.-Introduced as budwood from Mexico by the West
India Gardens, Altadena, California, in 1911. Propagated com-
mercially in Florida in 1917. Fruit pyriform, small to medium
size, 10-20 oz. Skin rather thick, slightly pebbled, dull green.
Flesh creamy yellow, greenish near the skin, of very rich flavor,
15 to 17 percent fat content. Seed medium size, tight. Season
December 1 to February 1. In California this is the only variety
recommended for commercial planting, and it already comprises
over 60 percent of the bearing acreage there. Under the con-
ditions existing in southern Florida, however, there are the same
objections to this variety as to the Mexican varieties, i.e., the
tendency toward uneven ripening of individual fruits and the
great susceptibility to attack by both scab and anthracnose.
Specimen trees and small plantings of Fuerte are to be found
in the central part of the state, and in general they have proven
rather unsatisfactory there. The tree is very resistant to cold,
but has been rather poor in growth and fruiting habits. The
variety is not at all desirable for southern Florida. In the Ridge
section a thorough investigation should be made of existing

Avocado Production in Florida 35

plantings before planting on a commercial scale. The variety
well merits trial, however, in the colder parts of the state, wher-
ever Mexican seedlings can be fruited, if only as a home fruit.

Fig. 18.-Fruit of the Lula variety.

Lula.-Originated on the place of George B. Cellon, Miami,
Florida, from a seed of the original Taft tree planted in 1915.
Fruited first in 1919. Propagated commercially in 1921. Fruit
pyriform or occasionally necked, medium large, 14-24 oz. Pack
12-18. Skin nearly smooth, light green. Flesh pale to greenish-
yellow, of very good flavor. Seed large but tight. Fat content
12 to 16 percent. Season December 1 to February 1. The
variety is precocious and very productive. The tree is a rapid
and thrifty grower and somewhat resembles Taylor in habit and
leaf, although the form is more spreading at the base. Both the
foliage and the fruit are highly susceptible to scab, but this can
be controlled by timely applications of spray. The variety has
proven very satisfactory both in the Ridge section and on the
lower East Coast, and it is recommended for planting for both

36 Florida Agricultural Experiment Station

Dorothea and Ward have recently been advocated for planting
in Hillsborough County. Neither has been tried either long or
extensively anywhere in Florida, and several years ago both were
dropped from the list of varieties recommended for home plant-
ings in California.
3. Mexican x West Indian hybrids, apparently, have been
fruited recently by W. E. Sexton, Vero Beach, Florida. It is still
too early to make any statements regarding the value of these
new hybrids, but they are being tried out carefully in Dade
Flower Behavior.The avocado has perfect flowers, each alike
capable of producing pollen and of developing into a fruit. In
spite of this fact, there is a pollination peculiarity which makes
it undesirable to plant solid blocks of single varieties. This
peculiarity is that the individual flowers do not shed pollen at
the time that the stigmas are receptive to pollen, and that all
the flowers open on all the trees of any given variety are in
the same condition at the same time. In every flower, the stigma
matures before the stamens are ready to shed pollen, and when
pollen is shed later by that flower, its stigma is no longer capable
of being pollinated. When the stigma is in a receptive condition,
the stamens are all lying down flat on the perianth segments,
while, when pollen is being shed, the three stamens of the inner
series are erect and clustered around the more or less withered
stigma and the other six stamens are partly upraised from their
former recumbent position. It is also easily possible to see with
the naked eye the uplifted flaps of the pollen chambers of the
stamens when pollen is being shed. Thus the flower acts as if
it were at first only female and later only male, and every tree
is first female and then male in function. And this is simultane-
ously true for all trees of any given variety-a condition known
as synchronous dichogamy, which the avocado exhibits to a
greater degree than any other plant known. But when some
varieties are acting as females, others may be acting as males;
and when the former are shedding pollen, the latter may be
receptive to pollen.
SThis basic principle was first announced by Nirody (13) who
came to Florida in the winter of 1921-22 to try breeding avocados.
He noted at once that flower opening and pollen shedding were
at different times of day for different varieties, but were at the
same time for all specimens of a given variety. Every day

Avocado Production in Florida 37

throughout the blooming period a new set of flowers opened for
the first time on every tree, but in some varieties this occurred
in the morning and in some in the afternoon. If the flowers of
a tree opened for the first time in the morning and were recep-
tive to pollen, they did not shed pollen until afternoon. If a
variety opened its flowers to receive pollen for the first time in
the afternoon, pollen was shed by those flowers during the next
forenoon, and this daily alternation of being male and female
he found to be very regular all through the blooming season.
Since the stigma of the pistil was usually not receptive to pollen
at the time when that variety was shedding pollen, he pointed
out that it was impossible for adequate pollination to take place
in the case of most varieties when planted in solid blocks. He
advocated the interplanting of varieties which would each shed
pollen when the other was ready to receive it, and he drew up
a brief list of such reciprocating varieties.
The extensive and careful researches of Stout (23, 24), origin-
ally undertaken to see if cross-pollination rather than pollination
in itself was needed by avocados for good fruiting, have added
very much to our knowledge of the peculiar flower behavior of
avocados. Following up Nirody's work during the next winter
in California, he discovered that, while Nirody was correct in
principle, the phenomenon was even more complex than Nirody
had realized. Making observations about once an hour or less
often, Nirody had found that flowers which had their first open-
ing in the afternoon closed for the night and opened again next
morning to shed pollen. He reported also that those flowers
which had their first opening in the morning remained open all
day and shed their pollen that afternoon. Stout made observa-
tions at more frequent intervals during the day on individual
flowers which he tagged, and discovered that every day there
were two sets of flowers opening on every tree. For the sake
of simplification he suggested that all varieties which opened
for the first time in the morning be grouped together in Class A,
and those having their first opening in the afternoon be grouped
into Class B.
On a tree of an A variety, Stout found the flowers opening
for the first time at some hour of the morning, depending on the
variety, as Nirody had reported. But all of these flowers closed
without shedding any pollen, and at some time during the after-
noon another set of flowers opened and shed pollen. The first
set did not open for pollen shedding until afternoon of the second
day, and so every day on every A variety tree there opened in

38 Florida Agricultural Experiment Station

mohhihg )afternoon \'i' morning afternoon
CLA VARIETY m e 78901121 23 4S6 8 10112 456789101112 23456

3 \ Mxxxxxxx
TAYLOR _2 \_____ti fna

1 xx----- cLosedfia
WNB LOWS-JL0 2,\\\\,, \.
BW1N5 LOWSO L2_ _____ ----A x ------- CLsed

Fig. 19.-Blooming cycles of avocado flowers during two consecutive days.
S=first or "female" opening of any flower-receptive to pollen.
=second or "male" opening of any flower-no pollen being shed.
---- =second or "male" opening of any flower-pollen being shed.
xxx =period during which flower is closed again between first and
second openings.

E T.AFT --..........
-1 LULA ... .
Q .IMMO 4......5..
P_ DUNEDIN .....T .

WIN5LoSON ....-.
'< "POLLOCK .-= .14 ...
-J LINDA -........
<" HARDEE .......... -

Fig. 20.-Normal daily bloom openings for various varieties of avocados.
-first or "female" opening of flowers-receptive to pollen.
-- =second or "male" opening of flowers-no pollen being shed.
---- =second or "male" opening of flowers-pollen being shed.

Avocado Production in Florida 39

the morning a fresh set of flowers to receive pollen and in the
afternoon a set to shed pollen which had opened previously on
the morning of the day before. In the case of the B varieties
the cycle was found to be as Nirody had reported, the same flow-
ers opening in the morning to shed pollen which had opened the
previous afternoon to receive it. In Fig. 19 is a graphic repre-
sentation of these flower-opening cycles for both A and B varie-
ties, while in Fig. 20 is a summary of the normal midseason
behavior of a number of varieties as respects flower opening,
adapted largely from Nirody and Stout.
The list of reciprocating varieties given by Nirody was greatly
amplified by Stout, who noted also that the flower behavior of
any given variety was the same in California as Nirody had
found it in Florida. However, he found also many eccentricities
of flower behavior under California conditions, notably those
shown by some B varieties which might have flowers not opening
to shed pollen until the morning of the second day. The obser-
vation of Nirody that cool weather retards equally the hour of
flower opening for all varieties was confirmed, but Stout also
found that sudden changes of temperature and cloudiness may
cause great irregularity in flower behavior. This observation
is of especial interest and importance in view of the possibilities
it affords for overlapping of the periods of opening of different
sets of flowers on the same tree in cool, cloudy weather, so that
some pollination may occur between flowers on the same tree.
Stout pointed out further that, in the case of B varieties which
open very late in the afternoon, the stigma of the pistil may still
be receptive to pollen next morning, since it has had little ex-
posure during the afternoon to the drying effect of sun and wind.
Such varieties have a theoretical chance of being self-pollinating,
and this may explain the fruitfulness of the Trapp in solid plant-
Clark (1, 2, 3) in 1923-26 also followed up Nirody's work by
California observations. He found that flower behavior in the
coastal region was commonly erratic, such as Stout had found
in the interior districts to be the case only in bad weather, so
that there was normally an extensive overlapping of sets of
flowers. Under these conditions the Fuerte proved quite self-
fruitful even when tented by itself, but other varieties which
apparently had an equal amount of overlap were not very self-
fruitful. The question arose in Clark's mind as to whether
varieties which normally set fruit well to their own pollen might
not be benefited by cross-pollination, either in obtaining a larger

40 Florida Agricultural Experiment Station

set of fruit or in holding better the fruit which was set. He
made several experiments with tented trees, introducing bees
under the cheesecloth tents which enclosed halves of two or more
trees of reciprocating varieties or half a single tree. Only a few
varieties were employed in these tests, most of the work being
done with Fuerte and Dickinson. In the case of the Fuerte, there
was no benefit found from abundant cross-pollination from sev-
eral reciprocating varieties, but the Dickinson showed definite
increase in fruit setting as the result of cross-pollination. It
should be noted that this latter variety showed little or no over-
lapping of different sets of flowers, whereas Fuerte showed this
in high degree.
In 1925 Stout continued his studies in the Homestead area of
Florida, where Nirody had worked, and E. B. Savage of the U. S.
Department of Agriculture joined him in the investigations (26).
They established the normal cycles of a large number of varieties
and confirmed further the identity of flower behavior in both
California and Florida for any given variety. With the advance
of spring, the hours of opening and closing of flowers advanced
uniformly for all varieties. Just as in California, sudden drops
in temperature caused great delays in the opening and closing
of flowers and often led to the overlapping of different sets. The
authors pointed out, however, that, while such overlap seemed
favorable to close-pollination, the conditions inducing the over-
lapping were also unfavorable to pollination because insects were
more sluggish and pollen and stigmas were less able to function
One of the most interesting results of this investigation was
the discovery that one of the most promising new varieties, the
Collinson, was unable to produce any pollen at all. Later studies
by Robinson (17) showed that when tented alone with bees this
variety set no fruit whatever, confirming expectations.
No attempts were made by Stout and Savage to cross-pollinate
varieties, but single trees of several varieties were tented with
hives of bees to see how self-fruitful they were. Tented Trapp
trees had a set of fruit about like untented trees, while Linda,
Panchoy and Taft produced much less fruit under tents than out-
side them. It should be noted that whole trees were used in this
work, and not half trees as in Clark's, so that the same tree did
not serve both for control and pollination test. The results,
however, seem sufficiently clear.
Stout visited the Homestead region again in the spring of 1932
to make further observations and added a number of new varie-

Avocado Production in Florida 41

ties to the lists of A and B groups (25). Working in conjunction
with him, Young (31) found that many avocado flowers have
defective pistils which probably could not set fruit to any pol-
lination. Studies of pollen tubes in pollinated pistils showed that
very few tubes ever reached the ovary, and gave rise to the
question of whether there are varietal differences in the rate of
pollen tube growth so that some varieties may be better pol-
linators than others.
Recently Skutch (20) has reported a few interesting observa-
tions on seedling avocados in Panama. In a group of eight trees
he found two A and two B varieties, but the other four were
conformable to neither group. These four were highly erratic
in flower behavior, often having only a single flower opening
and shedding pollen a few hours after opening. The trees which
showed regular behavior set good crops, while the trees showing
irregular flower behavior set very little fruit. The explanation
of these observations is very uncertain. The many seedling
trees which have been examined in Florida have always been
regular in flower behavior.
In connection with pollination problems, mention should be
made of the work of Van Elden, as reported by Hodgson (7).
He found in cytological studies of the avocado pistil that the
embryo sac was ready for fertilization at the first flower opening,
and that the egg had already been fertilized at the time of the
second opening, in some cases at least.
The following list contains the varieties likely to be found in
Florida groves and also some promising new ones.
Class A Varieties Class B Varieties
Blakeman Booth No. 3 McDonald
Booth No. 1 Booth No. 5 Nabal
Collinred B Booth No. 7 Nehrling
Collinson Booth No. 8 Nimlioh
Fuchsia Colla Northrop
Gottfried Collins Panchoy
Hawaii Dorothea Pollock
Kay Eagle Rock San Sebastian
Lula Fuerte Schmidt
Peterson Harman Steffani
Pinelli Itzamna Tonnage
Puebla ,Linda Trapp

42 Florida Agricultural Experiment Station

Hand Pollination.-Several workers have attempted to obtain
fruit from controlled hand crosses. Nirody (13) made several
thousand hand pollinations of a number of varieties, and reported
a set of about 10 percent. However, only two fruit matured from
all those laborious pollinations. One of these, a McDonald x
Pollock cross, has fruited and the name Nirody has been given it.
It has not proven very desirable for general planting. Stout
(23) made thousands of hand crosses in California in 1923, but
obtained a very low percentage of set; so far as is known, no
fruit matured from these crosses. Savage (18) reported that
he had obtained successful results from hand crosses in 1916,
but that the young seedlings were killed by the 1917 freeze.
In 1924 he made many more hand pollinations and obtained a
mature fruit from a Taft x Winslowson cross. The seedling
from this cross has not been reported to have fruited yet. In
1928 L. R. Toy made several hundred hand pollinations in the
Krome grove at Homestead and obtained two mature fruit to
the respective cross Trapp x Lamat and Winslowson x Colla.
These have not yet developed to the fruiting stage. Edward
Simmonds, at the U. S. Department of Agriculture Plant Intro-
duction Garden in Miami, reported a Trapp x Collason cross in
1921 to the seedling of which was given the name Trappson.
This fruited in 1924 and showed some desirable characters. It
will be seen that many thousand hand pollinations by several
investigators have produced a scant half dozen new hybrids of
definitely known origin, so that controlled crosses by hand pol-
lination are not a promising field of activity in avocados.
Insects and Pollination.-A number of insects are helpful in
pollinating the avocado, and this is fortunate, since the pollen
must normally be transferred from one tree to another, often
at a distance. Various flies and wasps are the carriers of pollen
in the native haunts of the avocado, and a number of flies and
other insects have been observed at work in Florida avocado
groves. Bees are very fond of avocado nectar, and probably
hives of bees in the avocado grove would assist in obtaining a
set of fruit, but no investigations have been made on this point
as yet. The bees do not tend to fly from tree to tree so much
as from hive to tree and return, whereas the wild insect pollen
carriers visit from tree to tree. Good crops are set consistently
in groves quite a distance from any bees, but it is quite possible
that a hive of bees per acre, with five set in the middle of each
5-acre tract, would materially increase production. There are

Avocado Production in Florida 43

too few large groves which are planted uniformly enough to
make possible testing of this theory in a conclusive way.
Interplanting Observations.-Because of the impossibility of
getting a reasonable percentage of fruit from hand pollinations,
and because of the length of time and amount of equipment
required for extensive tenting of reciprocal varieties, there are
few or no data available on the compatibility of different varieties
for pollination. Some observations have been reported on the
general need of interplanting to provide pollination by reciprocal
varieties, but the observations are few and somewhat conflicting.
Clark (3) reported no benefit to either variety when Fuerte
and Challenge, Fuerte and Blakeman, Fuerte and Spinks, or
Tingley and Harman were top-worked together, although these
pairs are all reciprocal in flower behavior and abundant insect
activity was manifest. Likewise a test made by Mrs. W. J.
Krome at Homestead in 1932, when Linda and Taft were tented
together with a hive of bees at one end of the tent, indicated no
mutual benefit as compared with untented trees.
Robinson and Savage (18) reported observations in Florida,
at Terra Ceia and at Lake Eloise, of marked increase in yields
when a reciprocating variety was provided. This was true of a
solid block of Fuertes which had been unfruitful for several
years. In this case it was reported that when Spinks trees came
into flower on one side of the Fuerte planting, there was a def-
inite gradation in Fuerte crop-setting, it being greatest next to
the reciprocating Spinks trees and diminishing steadily with
distance from them.
A large number of Lula trees on the Ivey Properties, Lake
Placid, is in solid block planting except for three scattered trees
of reciprocating varieties. Careful observations over several
years, however, have shown no evidence of differential bearing
of these Lulas, corresponding either with the location of these
scattered interplants or with the adjacence of a neighboring
block of mixed varieties. In the Homestead district two solid
10-acre plantings of Waldins, with Trapps adjoining on one side
in each case, are stated by the owners to have borne uniformly
well throughout the block and not to have borne more heavily
on the Trapp side. Another large block of Taylors planted sol-
idly is stated also to have fruited uniformly well, while the
authors have examined smaller blocks of Taylors which were
several hundred yards from any reciprocating variety and in
which every tree bore heavily. Even blocks of Collinsons five to

44 Florida Agricultural Experiment Station

10 rows deep have apparently fruited well throughout the block
without interplants.
Such observations by experienced growers have made many
of them skeptical of the need for interplanting reciprocating
varieties, in spite of undoubted need for it as indicated by flower
studies. Consequently the Sub-Tropical Experiment Station has
endeavored to collect accurate data on this question by actual
counts of fruit of thousands of trees in various groves where
A and B varieties are growing close to or far from reciprocating
varieties. Comparisons are only valid when made on a given
variety under different conditions of interplanting in the same
grove and for the same season. It is hoped that such data may
afford a more solid basis for statements regarding the need of
interplanting than can be given by casual observations only.
The following table gives the results of a few of the fruit
counts, where given varieties could be found separated in the
same grove by one or more rows from the nearest reciprocating
Rows Distant from Nearest No. of
Variety Reciprocating Variety Trees
1 ] 2 | 3 1 4 [ 5 Averaged
Collinson* ...................... 43 ........................................ 36 30
Linda .............................. 36 19 35 30 43 15
Taylor ............................ 58 55 59 40 43 7
Wagner .......................... 46 39 28 21 30 30
W aldin ............................ 147 ---- ....-...... ...-- ..- ....--... 123 30
W inslowson .................. 21 37 .............. 14 .............. 15

Interplanted with another variety of the same class.

In another grove, the planting is almost entirely of A varieties,
with another grove of mixed A and B plantings adjacent to one
end of the solid rows of the first grove. Counts were made of
the fruit on the two trees in each row nearest the mixed grove
and of the two farthest. The rows are 36 trees long. Results
are given in Table 4. The figure in parentheses after the variety
name indicates the number of trees whose fruit was averaged
for each count.

Avocado Production in Florida 45


Average Number Fruit on Waldin (22) Wagner (8) Lula (34)

Nearest pair ........................ 29 41 37
Farthest pair ...................... 7 31 50

A few other figures from the great number already collected
will indicate further the difficulty of drawing too definite con-
clusions. A small block of Taylors, seven trees deep, is bounded
on one side by a mixed planting and on the other by an orange
grove. Counts of fruit on 21 trees in the first, second, sixth and
seventh rows from the mixed planting showed average fruit per
tree as 70, 54, 44 and 36 respectively. In another grove a block
of 10 rows of Wagner is bounded on one side by Pollock and on
the other by Linda. The average fruit per tree in the two rows
nearest the Pollocks was 40, in the two rows nearest the Lindas
it was 29, and in the two center rows it was 38. Each count
represents the average of 60 trees.
In a third grove, which was not in good condition, Waldins
were alternated with another A variety for the first 15 rows,
with no avocados for half a mile on that side, while the last 40
rows have Waldin alternated with a row of mixed A and B
varieties. Counts of fruit on 60 Waldins in the first two rows
showed an average per tree of 14 fruit, while on the 15th and
17th rows, interplanted with reciprocals, the average tree count
was 12.
From these and many other data obtained in fruit counts on
thousands of trees, it seems clear that, while maximum yields
cannot be expected from solid plantings, nevertheless there is
not necessarily or clearly any advantage in having reciprocating
varieties closer than three or four rows. There seems also to be
some difference between varieties with respect to their ability
to set crops in more or less solid plantings. Waldin, Lula' and
Taylor seem to be as well able to do this as is Trapp, while
Wagner, Winslowson, Linda and Schmidt seem to have greater
need of interplanting than the group just mentioned, and seem
to show some correlation between the amount of crop yield and
the distance from reciprocating varieties. The problem still
requires for its solution, however, the keeping of accurate yield
records over a period of years.

46 Florida Agricultural Experiment Station

During the past five years there have been made a great many
analyses of fruits of a large number of avocado varieties. The
results of the very careful study of the changes taking place
in the avocado from early in its development until full maturity
for the commercially important varieties have already been
published (21). In Tables 5 and 6 are given the condensed
results of determinations of fat, sugar, protein, ash and moisture
content of the 12 most important Florida varieties. These de-
terminations were made on the fresh pulp of mature avocados,
and are expressed in percentage composition of this fresh pulp-
except for the figures giving the fat content expressed on the
basis of the dried pulp-and so represent the constitution of
the avocado as consumed. The methods used in making these
analyses have been described fully in the publication referred
to above (21). There are also given in these tables interesting
data on the proportions of the whole fruit which are skin, seed
and pulp. For ease of comparison, the data of these tables are
presented graphically in Figures 21 and 22. In Table 7 are given
the determinations of the fat, ash and moisture contents, and
the proportions of seed, skin and pulp, for a number of varieties
of little or no commercial importance at present.

% 00-7 r zl F7ZI
90- SEED

70- SKIN

30- PULP


: g

Fig. 21.-Proportions of seed, skin and pulp for standard varieties of
avocados. (See Table 5.)

(Averages of 10 to 100 mature fruits, Green Basis)*
% -%
Rank Variety Weight Variety %0 Variety Skin Variety Edible Variety %
S(pounds) Seed I___ ___ Pulp__ Ash
1 Linda 1.71 Linda 8.56 Pollock 9.42 Linda 77.72 Winslowson 1.23
2 Pollock 1.59 Simmonds 12.50 Trapp 9.53 Simmonds 77.22 Wagner 0.99
3 Winslowson 1.48 Schmidt 12.71 Waldin 10.13 Pollock 75.92 Collinson 0.96
4 Simmonds 1.39 Eagle Rock 14.67 Simmonds 10.71 Collinson 74.82 Linda 0.93
5 Eagle Rock 1.37 Pollock 14.68 Winslowson 10.72 Trapp 72.15 Lula 0.92
6 Collinson 1.37 Collinson 15.87 Collinson 10.94 Winslowson 72.12 Taylor 0.87 '
7 Waldin 0.99 Winslowson 17.17 Lula 12.60 Schmidt 71.84 Schmidt 0.86 g.
8 Lula 0.94 Trapp 18.32 Wagner 12.86 Eagle Rock 71.03 Pollock 0.81
9 Trapp 0.93 Taylor 20.83 Linda 13.75 Waldin 65.57 Eagle Rock 0.80 .
10 Schmidt 0.93 Wagner 22.91 Eagle Rock 14.30 Taylor 64.79 Simmonds 0.72
11 Wagner 0.72 Waldin 24.31 Taylor 14.37 Wagner 64.24 Waldin 0.70
12 Taylor 0.67 Lula 24.36 Schmidt 15.44 Lula 63.32 Trapp 0.64

Varieties ranked under each classification according to percentage composition.


(Averages of 10 to 100 Mature Fruits)*

% Fat and Oil (Ether Extract) Total %
Rank Variety % Variety Sugar Variety Protein 'j
Moisture Variety Green Variety Dry (Green (Green
Basis I Basis Basis) Basis)
1 Wagner 72.47 Wagner 18.77 Wagner 67.46 Simmonds 1.92 Simmonds 1.71
2 Lula 73.89 Lula 13.60 Linda 58.66 Eagle Rock 1.85 Taylor 1.40 .
3 Taylor 76.89 Winslowson 13.02 Winslowson 58.31 Winslowson 1.80 Eagle Rock 1.34
4 Eagle Rock 78.06 Taylor 12.81 Eagle Rock 55.12 Lula 1.78 Lula 1.21
5 Winslowson 78.08 Linda 12.32 Collinson 53.80 Trapp 1.56 Trapp 0.90
6 Linda 78.74 Eagle Rock 12.18 Taylor 53.38 Taylor 1.52 Winslowson 0.86
7 Collinson 79.44 Collinson 11.55 Lula 53.30 .
8 Waldin 82.37 Schmidt 7.21 Schmidt 39.97
9 Schmidt 82.55 Simmonds 6.63 Simmonds 37.12
10 Trapp 83.53 Waldin 6.34 Trapp 35.61
11 Simmonds 83.88 Trapp 5.91 Waldin 35.37 "
12 Pollock 85.05 Pollock 4.77 Pollock 31.39

Varieties ranked under each classification according to percentage composition.

Avocado Production in Florida 49

s t fat content on dty weight basis
00oo1. geen weight basis
Moisture content


30-- I

Ij Z

avocados. (See Table 6.)

There is a considerable difference between the lowest and the
highest fat content shown in these tables, and there is no abso-
lute correlation between fat content and race. In general the
West Indian varieties show from 4 to 7 percent of fat, the Gaute-
malan varieties from 10 to 13 percent, and the Mexican varieties
from 12 to 15 percent, but there are exceptions in all three races.
It is of interest to find that the same variety almost invariably
shows a fat content several percent higher in California analyses
than in Florida analyses, a condition undoubtedly due to climatic
conditions and to the difference in time required to reach ma-
turity. One variety, the Dorothea, has analyzed several points
higher in Florida, and the Linda, a comparatively late maturing
variety in Florida, shows the same analysis in both states. The
other varieties mature in much shorter time in Florida than in
California, and the studies of the changes during fruit develop-
ment have shown that there is a steady increase in fat content
while the fruit remains on the tree, even if it is allowed to hang
until well past the normal harvesting time for the variety.

50 Florida Agricultural Experiment Station

% Fat
Varity Weight % % % % and Oil %
(pounds) Seed Skin Edible Moisture (Ether Ash
______Pulp Extract)

1 Atlixco............ 1.21 16.3 15.3 68.4 80.1 12.9 1.05
2 Blakeman........ 1.29 10.4 10.1 79.5 85.7 7.8 0.99
3 Booth No. 3.... 1.00 17.4 13.7 68.9 82.3 10.2 1.23
4 Booth No. 5.... 1.20 18.2 14.0 67.8 80.2 9.7 0.85
5 Booth No. 6.... 1.16 19.3 13.9 66.8 81.8 8.6 0.84
6 Booth No. 7.... 0.85 19.1 16.4 64.5 83.4 7.2 0.77
7 Booth No. 8.... 1.07 15.4 12.4 72.2 81.7 8.6 0.80
8 Booth No. 9.... 1.03 20.1 14.3 65.6 78.4 11.9 0.91
9 Cantel ............ 1.05 9.4 15.2 75.4 80.2 10.6 0.84
10 Collinred.......... 1.22 15.7 11.5 72.8 75.7 18.3 1.07
11 Collins.............. 0.70 12.5 15.4 72.1 79.4 12.2 1.01
12 Dorothea.......... 0.60 21.7 9.0 69.3 72.8 19.5 1.00
13 Fuerte.............. 0.81 15.0 14.8 70.2 78.1 15.6 0.89
14 Garcia.............. 1.07 16.1 6.7 77.2 78.7 11.2 0.99
15 Gottfried ........ 0.61 9.0 9.2 83.8 81.0 11.6 1.20
16 Hosack ........... 1.19 12.8 13.9 73.3 79.5 9.6 1.04
17 Itzamna .......... 0.95 9.1 13.5 77.4 80.1 10.7 0.97
18 Nirody ............ 1.22 20.4 12.5 67.1 81.4 10.5 0.72
19 Panchoy .......... 1.21 9.5 14.8 73.7 80.3 11.4 0.93
20 Peterson.......... 0.78 17.8 7.3 74.9 85.2 6.7 1.54
21 Pinelli............ 1.30 12.9 12.6 74.5 82.3 8.4 0.80
22 Puebla............. 0.89 17.4 8.9 73.7 78.1 14.2 0.99
23 Roberts.......... 1.00 18.2 12.8 69.0 84.3 6.0 0.71
24 San Sebastian 0.91 17.3 9.8 72.9 78.3 13.2 0.89
25 Solano............. 1.14 19.1 13.5 67.4 85.7 6.9 0.90
26 Stevens........... 0.70 14.9 12.9 72.2 80.2 7.5 0.89
27 Taft.............. 1.12 16.3 12.8 70.9 80.4 10.4 0.92
28 Winslow ....... 0.73 15.4 19.2 65.4 79.9 11.7 1.02

Avocado Production in Florida 51

Two very interesting phases of these developmental studies
may be mentioned very briefly here, although the above bulletin
should be consulted for detailed analyses. Analyses for the
season 1930-31 showed consistently higher fat content for the
same date than the analyses for 1931-32. This difference was
about 2 percent for the varieties with comparatively high fat
contents, and about 1 percent for those with low fat contents.
The only exceptions were the Waldin, which was equally high
both seasons, and Pollock, which was higher in 1931-32 by 1
percent. This seasonal difference is doubtless the result of dif-
ference in time of setting fruit and hence in the length of de-
velopment time during the two seasons. In this connection it
may be noted that Pollock blooms exceptionally early, and may
have set fruit earlier in the same season when other varieties
had a late set.
It is impossible to make definite statements regarding the
cause of the differences noted, but the fact of the seasonal varia-
tion in fat content is of importance and so is the small amount
of this variation. The variation shown in fat content of fruit
grown in different localities is much less for any given date than
the variation on this date from one year to another, but is less
than 10 percent of the total fat content of the fruit in either case.
The other point of interest is the finding that fruit stored
until soft after picking showed consistently about 2 percent
higher fat content than fruit analyzed at once after picking on
the same date. This difference was rather uniform all through
the season for all varieties tested. In part it is due to loss of
the water from the fruit by evaporation, but this is not the only
factor involved.
There is no correlation at all between high fat content and
good quality, so far as comparison of varieties is concerned. Two
of the finest varieties for eating are the Trapp and Pollock, both
of which are low in fat. Collinson and Linda are almost equally
esteemed, however, and they have twice the fat content of the
other two, while some varieties which are low and some which
are high in this constituent are distinctly mediocre in palatabil-
ity. It is of some interest to note that high fat content is almost
always associated with high ash content, while there is no rela-
tion between fat content and the amount of sugars or protein
contained in the fruit. Trapp and Simmonds are similar in fat
analysis, but the former runs comparatively low in sugar and
protein, while the latter runs high in both. There still remains
the necessity of correlating the fat content of the individual

52 Florida Agricultural Experiment Station

variety with its palatability, that we may have a satisfactory
basis for determining maturity. Since there is no necessary
connection between fat content and quality, we must find out
the time at which each variety acquires maximum quality, to
make possible the assigning of a definite fat content and time
of year for proper maturity.
These analyses may be more significant if we compare the
avocado with other well-known fruits. The apple, banana, black-
berry, cherry, grape and mango are fruits which have many
similarities to the avocado and one important dissimilarity. In
content of water, protein, ash and energy, these fruits are very
similar to the avocado, but they all have their energy derived
chiefly from sugars while the avocado food energy is stored
principally as fat.
The avocados of Florida range in water content from 72 to
85 percent, which compares well with the range of from 75
percent for bananas to 85 percent for blackberries, and inter-
mediate percentages for the other fruits. The protein of the
avocados constitutes from 0.85 to 1.70 percent of the fresh pulp,
while in the sweet fruits it ranges from 0.3 percent in apples
to 1.4 percent in grapes. Florida avocados would seem to be
comparatively rich in proteins among fruits. The ash content is
a measure of the mineral salts contained in the fruit. In the
avocado varieties it is seen to be from 0.65 to 1.25 percent, as
compared with from 0.30 percent in apples to 0.84 percent in
bananas. Florida avocados are comparatively high in mineral
content, among energy-producing fruits.
The fat or oil content of Florida avocados makes up from 4 to
20 percent of the weight of the fresh pulp, and this seems at
first glance to compare well with the range of sugar content in
the sweet fruits above listed, from 6 percent in blackberries to
20 percent in bananas. The energy value of fats, however, is
more than twice that of carbohydrates, so that avocados of a
given fat content contain over twice the calories contained in
fruits showing an equal percentage as sugars. Thus our West
Indian varieties compare in energy content with apples, cherries,
grapes and mangoes, while our Guatemalan varieties mostly
exceed bananas in fuel value.
The sugar content of all avocado varieties is the lowest found
in any fruit of which we have analyses, and there is less variation
among the different varieties in this respect than is the case for
any other constituent of the fruit. The range is only from 1.5
to 2.0 percent. This range of values may be compared with the

Avocado Production in Florida 53

0.2 to 1.4 percent of fat found in the sweet fruits, which pro-
duces an amount of energy quite comparable to the energy of
the avocado sugar. This extremely low sugar content of avocados
is a very important feature of their constitution.

Nursery Practice.-As has been noted previously, the avocado
was propagated exclusively by seed until 35 years ago, and in
tropical countries that is still the usual method, but, as seedling
groves have great variability in the quality and quantity of fruit
produced by different trees, a method of vegetative propagation
must be employed to insure reproduction of any given variety.
Cuttings of avocado have proven difficult to root, although the
experiments along this line have not been very extensive. Bud-
ding and grafting are the methods of propagation employed for
the avocado by nurserymen in Florida.
Seeds of the West Indian race are imported in great quantity
from Cuba to provide nursery stocks, although seeds of any cull
fruit of any variety or race produced locally are also used. They
are viable for two or three weeks after being removed from the
fruit, if kept in a cool, dry place. Seeds planted in the early
part of the season, if from mature fruit, have the advantage
of warm weather to hasten their germination and growth. Very
small seeds should be discarded, even though of normal size for
the fruit from which they are taken, since the size of the seed
indicates the amount of food stored for the young seedling.
For box-grown trees in the slat-house, seeds may be sprouted
in shallow beds of sawdust and transferred to boxes as soon as
they have sprouted, or may be planted at once in the boxes.
Seeds should be planted so that the end which was nearest the
stem of the fruit is up. In pointed seeds the point should be up.
Standard avocado boxes are usually made of 5/8" pecky cypress
and are 6"x6" in cross-section and 12" deep. They are filled
with a sandy loam containing a light sprinkling of commercial
fertilizer. Good drainage and regular watering are essential to
successful growing of seedlings, and seeds are best covered not
more than half an inch.
Seeds may also be planted 18" apart in nursery rows in the
open, when the soil is of sufficient depth and irrigation can be
provided, and the seedlings are then budded or grafted in the
nursery row. These rows should be 4 ft. apart to allow for
cultivation. Young seedlings are more susceptible than older

54 Florida Agricultural Experiment Station

trees to injury from low temperature, and some protection must
be given to stock grown in the open when damaging frosts or
freezes are experienced.

Fig. 23.-Interior of avocado nursery slat-house.

Until recent years the avocado has been propagated in Florida
nurseries usually by shield-budding, the same method used in
citrus nurseries. This operation, however, requires much care
and experience for success, and even experienced citrus budders
are frequently unsuccessful in their first attempts at budding
the avocado. When the work is properly done, a high percentage
of avocado buds unite with the stock. The most important factors
are the condition of the budwood and of the stock. Seedlings
for budding should be kept in a thrifty growing condition, and
any unthrifty or weak seedlings should be discarded. Vigorous
seedlings should have reached budding size-3/16" to 1/4" in
diameter at the base-within three or four months after plant-
ing. The best season for budding in Florida is from November
through March, preferably November and December. Budwood
should be selected from well-matured terminal growth, preferably

Avocado Production it lorida 55

from twigs which are just ready to put out a new flush of growth.
The wood should be sufficiently matured that it does not snap
readily on bending. The best buds are those which are plump
and show no sign of having started growth, although the ter-
minal bud shows this. Budsticks should be cut from healthy
trees which are known to bear satisfactory crops.
The bud is cut in the form of a shield from 1 to 11/2 inches
long, depending on the size of the stock. A very sharp, thin-
bladed knife should be used, and the cut should be made with a
single smooth, sliding stroke. Most propagators carry a heavy
razor strop and renew the knife edge after cutting every 25 or
30 buds. The union depends largely upon close contact of the
cambium tissues of the bud and of the stock, and buds which
have been gouged out or cut with a rough contact surface have
little chance to unite properly. The cut in the stock, whenever
the bark slips readily, is made in the form of an inverted T, the
cross cut being slanted slightly upward. The bud should be
inserted immediately after it is cut, to avoid drying out of the
tender cambium, and should be allowed to complete the opening
of the slit by its own entrance. After insertion of the bud, the
stock is wrapped with waxed cloth or raffia. Within four or five
weeks the wraps must be examined and removed or loosened if
necessary to prevent binding the stock. At this time the top of
the seedling stock should be pinched out to force the bud into
development. A few weeks later the stock may be cut off just
above the union and the cut surface covered with grafting wax
or asphalt paint. Stock sprouts which arise above or below the
bud should be pinched out. The bud should be inserted in the
first few inches above the ground level.
Grafting haslargel superseded budding in Florida avocado
nurseries in the last few years. The time required for producing
a tree of planting size is lessened considerably by grafting, and
some varieties difficult to bud-especially Taylor, Wagner and
Simmonds-are easily grafted. Also it is much easier to find
suitable graft scions than suitable budwood, and there is less
danger of buds being shed. Stocks of lead-pencil size may be
grafted by whip-grafting and even more slender ones by side-
grafting. Terminal scions or "tips", 2 to 21/2 inches long are
used and they should be from the last matured growth just as
it starts to flush. However, there is more latitude of choice
possible in selecting twigs more or less mature than there is in
selecting budwood. The buds and leaves along the lower part
of the scion are cut off closely so that the wraps will fit tightly.

56 Florida Agricultural Experiment Station

Fig. 24.-Side-grafting avocados. A, seedling suitable for grafting; B,
making the incision; C, scion inserted; D, the complete graft wrapped with
rubber band; E, complete graft after scion has started growth (left) and
the stock cut back (right).

Avocado Production in Florida 57

Either very thin waxed cloth or No. 63 rubber bands are used
for wraps. The bands possess the advantage of giving adequate
pressure and exclusion of water without danger of injurious
binding of the tender stock and scion.


Fig. 25.-Cleft-grafting avocados. A, making the incision; B, scion
inserted; C, completed and wrapped graft.

Side-grafting is the easier and more popular form of nursery
propagation. For this it is especially important that the tissues
of the stock shall not be too mature, since the scion is inserted
in the center of the stock. Seedlings suitable for grafting are
shown in Figs. 23 and 24A. The scion is cut with a long, wedge-
shaped lower end, and this is inserted in a long, sloping cut made
diagonally down into the stock, as shown in Fig. 24B. The scion
should be inserted so that all of the cut portion is enclosed.
After the scion and stock have united, the seedling top is treated

58 Florida Agricultural Experiment Station

as for budded stocks (Fig. 24, D and E). In case of the failure
of the graft to take, the stock may still be cleft-grafted lower
down (Fig. 25).
Whip-grafting offers an even larger surface of contact for the
cambium layers of scion and stock than does side-grafting, but
it involves cutting off the top of the seedling stock at the time
of grafting, and in case of a failure of the graft, it is necessary
to let a new top develop on the stock. It can be used successfully
for older stocks than can side-grafting.
A few other methods of grafting have been employed for avo-
cados, but none of these is in general use or offers any advan-
tages over those described above. So-called "seed-grafting" was
introduced about 15 years ago by the late John Beach, but never
attained favor. Seeds were sprouted in sawdust and bench-
grafted with tender tips as soon as the young plumule attained
an inch or two of length. No opportunity is afforded for dis-
carding weak stocks in this method.
Whether budwood or scions are being cut, it is very important
that the propagating material should not be allowed to dry out.
Budsticks can be held for a time by sealing the cut end in paraf-
fin and keeping the stick in slightly moist sphagnum or peat
moss. The more tender tip scions should be put at once into
this medium to keep them from wilting.
The young trees are fertilized with light applications of a
fertilizer high in ammonia and low in potash, such as 5-7-3 or
6-6-3. Occasional applications of liquid manure also are bene-
ficial. Trees grown in boxes in slat-houses require no further
attention until they are large enough to plant. Field-grown
trees may be taken up about a year after budding and re-
established in 8 or 10 inch boxes in the slat-house, to develop
new roots before being set out in the field. Balled and burlapped
trees partially defoliated are quite successfully transplanted
from the field nursery to the grove. Trees grown in the open
are stockier than shade-grown trees, and, being accustomed to
full sunlight, they need not be shaded when planted in the grove
except during the hot summer months, although shade is always
Rootstocks.-It is customary in this state to use West Indian
seedlings as stocks on which to bud or graft the avocado. Seed-
lings of this race are generally vigorous, although there is some
variation in this respect. Seeds taken from fruit of Guatemalan
varieties growing near West Indian varieties usually make thrifty
seedlings also, perhaps due to "hybrid vigor". Some Mexican

Avocado Production in Florida 59

seedlings are of exceptionally vigorous growth, while others are
not at all so. Guatemalan seeds and scions appear to succeed
equally well on stocks of all three races, but West Indian varieties
usually are unsuccessful on Mexican stock, although successful
on West Indian and Guatemalan seedlings. There is little accu-
rate information available concerning racial and varietal com-
patibilities of stock and scion, although doubtless certain definite
differences exist. How important these relations are can be
determined only by carefully planned investigations extending
over many seasons. For the present, Cuban seedling stocks,
variable in vigor though they are, offer the most satisfactory
material for commercial propagation, but Guatemalan stocks
may confer slightly more cold resistance for plantings in central
Top-Working.-As has been the case in many other fruit
industries, the earlier plantings of avocados in Florida contained
many unproductive and inferior seedlings, and many of the
propagated varieties have proved unsatisfactory after extended
trial. No consistent, organized interest has been maintained in
the study and standardization of varieties, and in consequence
growers are now resorting to extensive top-working of the un-
satisfactory varieties and seedlings. No attempt should be made
to top-work trees in poor condition unless that condition is due
to a temporary lack of fertilizer. It is more economical in the
long run to replace unhealthy trees with thrifty nursery trees
than to attempt to work them over.
It was formerly considered very difficult to graft avocado
trees of bearing age, and budding was the only method available
for top-working. A method of cleft-grafting has now been de-
veloped, first suggested by Manning (9) and amplified by Elliott
(6), that has given excellent success in Florida when the work
is done during the cooler season of the year. December and
January are the best months for grafting in Florida, but the
process may be carried on until April, although the percentage
of success is likely to decrease steadily as the season advances.
Grafts have been made with success in July, but the chances
are too great against success for this to be done except in emer-
gencies. Grafting is a more detailed and slower process than
budding and involves a greater outlay for equipment, and so
shield-budding is still employed in top-working by many growers.
It usually takes longer, however, to produce a bearing tree by
budding than by grafting, and so the latter method has steadily
gained favor (Fig. 28).

60 Florida Agricultural Experiment Station

Fig. 26.-Top-working avocados by cleft grafting. A, making the cut;
B, opening the cleft; C, trimming the cleft; D, inserting the scions; E,
removing the wedge. (See Fig. 27 for final steps in the process.)

Avocado Production in Florida 61

For cleft-grafting, scions should be chosen from more mature
growth than is used for budwood, preferably from the second
or third flush back from the tip. They should have a diameter
of %/8 inch or more and are preferably cut about 6 to 8 inches
long. The upper portion should have at least two plump, dor-
mant buds, and the lower half must be fairly straight. Trees
to be grafted are sawed off 1 to 4 feet above the ground, depend-
ing on the diameter of the trunk. If several large limbs are
present with diameters of 3 inches or more, the cuts should be
made on these limbs a foot or more above their insertion so
that they form the framework for the new tree. Some propa-
gators prefer to leave several "nurse" limbs, but this is not
essential to success. Experiments in which one-third, two-thirds
and all of the limbs have been removed at the time of top-working
have shown no striking differences in result. The cleft is made
with a saw (Fig. 26A) and should be 3 to 5 inches deep, accord-
ing to the length of the scion. The portion of the stumps
through which the cut is made should be straight and free from
knots at the sides of the cleft. A hardwood wedge is driven into
this cleft until the trunk beneath the cut begins to split (Fig.
26B). The sides of the cleft should be pared thinly to remove
sawdust and make a smooth surface so that the cambium layers
of stock and scion may fit snugly and make close contact (Fig.
The scions are trimmed to a wedge shape along the lower
portion (Fig. 26D) leaving them slightly thicker on the edge
which is to be on the outside of the cleft, so that the cleft will
not be held open by the inner edge and the cambium layers
prevented from coming close together. A scion is placed in the
cleft at each side (Fig. 26D) and fitted carefully down into place
so that the cambium layers of scion and stock coincide as fully
as possible. In this connection, it must be remembered that
the bark of the stock will be much thicker than that of the
scion, and that it is the juncture of wood and bark which must
be in contact in both cases. When the scions are tightly fitted,
the wedge is withdrawn entirely in the case of small stocks of
less than 3 inches diameter, leaving the pressure of the closing
cleft to hold the scions in place (Fig. 26E). In large stumps,
however, this pressure will be too great for the scions, and the
wedge is withdrawn only far enough to insure a tight holding
of the scions by the cleft. The top of the wedge may then be
sawed off flush with the stump. To prevent decay, it is essential
that all cut surfaces be coated with a grafting compound (Fig.

62 Florida Agricultural Experiment Station

27F) and the cleft filled also (Fig. 27G). The scions also should
be coated where they are in the cleft. A strip of heavy paper
is then tied around the stub (Fig. 27H) projecting several inches
above the tops of the scions, and filled with a mixture of sand
and peat moss (Fig. 271). This is watered lightly at intervals,


Fig. 27.-Final steps in top-working by cleft grafting. F, painting the
scions and exposed stock surfaces; G, filling the cleft with grafting com-
pound; H, protecting the completed graft from sun and wind; I, putting
damp peat moss in the graft collar to keep the scions moist.

Avocado Production in Florida 63

to prevent drying out of the scions before they have united with
the stock. It is advisable also to bend a small strip of paper
as a cap over the open cylinder, to give additional protection
against the sun, but holes for ventilation should be made at the
top and bottom of
the cylinder also.
These cylinders
may be left in -
place indefinitely,
as they afford
protection against
cold as well as
against sun and
The grafting
compound com-
monly used in
Florida is a mix-
ture of 4 parts
beeswax with 1
part paraffin.
Some prefer to
add a small piece
of carnauba wax,
about an inch in
diameter, to each
pint of the above
mixture in order
to raise the melt-
ing point some- "0
what. This is de-
sirable especially
when the work is
done in the warm-
er spring months,
but is not essen-
Fig. 28.-Scions 12 months after grafting. These
tial to success. were on a very vigorous seedling stock.
Results equal to
those obtained with the beeswax-paraffin mixture have also been
obtained by use of a proprietary asphalt emulsion (Tree-seal).
This is no more expensive to use and requires no heating.
The following tools and materials are required in top-working:

64 Florida Agricultural Experiment Station

Carpenter's saw, adjustable pruning saw (known as California
saw), hand pruning shears, hardwood wedges, roll of heavy
building paper 15" wide, heavy twine, labels, pencil, whetstone,
mallet or hammer, very sharp thin-bladed knife, a mixture of
sand and peat moss, and the grafting compound. If the beeswax-
paraffin mixture is used, there must be added a melter for the
wax. Patented wax melters are on the market and are well worth
their cost when much grafting is being done. Care should be
taken not to apply the wax too hot.
For top-working avocado trees by shield-budding, the tree
should be cut back in early winter to the main framework of
large limbs. The closer to the ground the new limbs can be
placed, the better. A few branches should be left growing below
the cut, to keep the roots in good condition. In about two months
after cutting back, sprouts will have grown from the stumps
and will be ready for budding. A good many sprouts may be
budded on each limb, and after they have "taken" and grown
off, selection can be made of the most desirable ones for perma-
nent limbs.
Budding is done just as described under Nursery Practice,
except that, because the stocks are growing much more vigor-
ously than nursery stocks, the wraps must be examined within
two weeks after budding to be sure they are not binding. These
sprouts may also be worked by the side-graft or whip-graft
methods, as for nursery stocks, or by a specialized form of side-
grafting known as shield-grafting or "sprig-budding". The cut
in the stock is made just as for shidld-budding with an upright
T, but instead of a shield bud, there is inserted a terminal scion
with the lower portion cut to a wedge by trimming from one side
only and this side placed next the cambium of the stock.

Planting Distances.-The spacing of trees in the grove should
be governed somewhat by the varieties planted, by the type of
soil, and to some extent, by the shape of the grove tract. Trees
tend to grow larger in rich soil than in poor, and should be
spaced more widely where known to grow larger. Likewise,
some varieties grow tall and slender and may be spaced closer
than varieties with a wide spreading habit of growth. On the
whole, however, it is unwise to adopt several spacings in the same
grove, since, if top-working to other varieties is later desired, the
close spacing of originally slender trees may cause inconvenience.

Avocado Production in Florida 65

The earliest plantings of avocado trees in Florida were in
places where there was an abundance of soil, such as large pot-
holes, and the seedling trees grew quite large. Consequently,
the first seedling groves, and also the first groves of budded
stock, were set out with spacings of 30 feet between trees, giving
about 50 trees to the acre. As these groves matured, it was
realized that such wide spacings were wasteful, and many of
these older groves were later interplanted. The practice now
is to plant the trees. about 20 feet apart, and there is even a
tendency to plant more closely than this, one way. Where the
trees are planted close, the ground is shaded more completely,
and this prevents burning of the humus from the soil so rapidly,
with resultant benefit to the roots and to the water-holding
capacity of the soil. The avocado is native to lowland and high-
land forests of the tropics, where partial shade, a carpet of fallen
leaves, and wind protection are present. The grower may well
attempt to duplicate such conditions so far as is consistent with
economical and efficient handling of the grove. Wider spacing,
30 feet or so, should be allowed every six rows, to provide road-
ways through the grove.
Preparation of Land for Planting.-In Dade County, where is
grown the bulk of Florida avocados, the soil is peculiar in consist-
ing of a more or less hard oolitic limestone containing numerous
pockets of sand or red clay. In the Redlands district, the oolite
crops out all over the surface, so that only in pot holes of varying
size is there any tillable soil. Further north, sand often overlies
the rock to a depth of from two inches to two feet. Early plant-
ings were made in deep sand or in potholes of soil, but it was
impossible to set out a grove in straight rows when only potholes
were employed. The next step was to dig shallow holes in the
rock where the trees should go and fill in around the trees with
surfaced soil. At yearly intervals the rock was chipped further
back in a band just outside the root zone. Still later the practice
of blasting holes with dynamite came into vogue, and this is
still a standard method.
There is no generally accepted depth of tree hole preferred by
all growers, some insisting on deep blasting and some on shallow.
The most common practice, however, is to make a shallow hole.
Four or five charges of 1/4 stick of dynamite each are placed in
holes drilled 18 inches deep and spaced equally in a circle of 2 ft.
radius with the center where the tree is to be. This breaks up
the rock to a maximum depth of 3 ft. at the center and forms
a bowl tapering off at the sides. The broken rock is cleaned out,

66 Florida Agricultural Experiment Station

some fragments are replaced in the bottom of the cavity, and
the hole is filled again with surface soil. Two or three shovels
full of well-rotted animal manure should be thoroughly mixed
with the soil in each hole some weeks prior to planting.
The earlier groves were set out among the stumps of the pine
forest which covered the ground, and these groves often bore
excellent crops, but grove cultural operations were rendered dif-
ficult by the stumps, and so it has become the practice to clear
and scarify the land. The scarifier is a massive frame carrying
several rows of pointed steel bars one inch square. These rows
are spaced about 9 inches apart, and the weight of the carriage
keeps them in the ground when meeting obstruction. Pulled
by a 60 H. P. track-type tractor and followed by a steam roller
to crush the rock fragments, or pulled by a large steam tractor
which accomplishes both functions at once, these scarifiers break
up the rock to a depth of 4 to 6 inches and leave a surface layer
of mingled rock and soil in which the roots can spread and feed.
It is usually necessary to scarify a piece of land four times in
order to get it into good condition.
A recent innovation in hole preparation consists of scarifying
the ground to a greater depth than that above mentioned along
the tree rows in both directions. Underneath the trees the
ground is scarified to a depth of 9 to 10 inches, and soil is also
mounded up from either side of the row, so that there is over
a foot of soil in the place where the tree is to stand, besides a
uniform soil depth all over the grove of 4 to 6 inches. No groves
planted thus have reached maturity, but the method seems sat-
isfactory and has been widely followed in the last two or three
On the deeper sandy soils of the other parts of the state, the
same method of land preparation is followed for avocados as for
citrus, except that compost is mixed in the soil of the tree hole.
It is decidedly worth while, where possible, to prepare the land
a year in advance of planting, and to grow a heavy cover crop
before planting. An even better plan is to crop the land to
winter tomatoes, following these by a rank cover crop growth
during the summer, and then plant the trees the following spring.
Time of Planting.-Avocados may be planted successfully in
Florida at any time of year, at least in the sections where com-
mercial culture is practiced, provided precautions are taken
against certain seasonal weather conditions which follow the
setting of the trees. Much more expense is entailed, however,
in setting out at some seasons than at others. The best season

Avocado Production in Florida 67

for setting avocados is during the spring months, from early
April to early June. The temperatures at this season favor
growth and the amount of watering to be done is likely to be
small. The cost of watering newly planted trees becomes very
great when trees are planted during a dry season.
Trees set in October are likely to have good weather conditions
for getting established, since abundant rains can be expected
during this month and the temperatures are no longer those of
summer. The winter months which follow are the driest of the
year and watering must be done fairly regularly all winter. Fur-
thermore, the newly established trees are the most easily injured
by cold weather, whereas trees set out in early summer or late
spring are well enough established and have matured their first
flushes of growth sufficiently by winter to be a little hardier
than newly set trees. The grower planning to set out trees in
late autumn should be prepared to give them some protection
from cold in case of frost. In the central and northern parts
of the state avocados should be banked like citrus trees during
the winter, and fall planting is somewhat more hazardous in
these areas. Trees planted in mid-summer require more care
in shading than trees set in the fall or spring.
Interplanting and Variety Selection.-There is no evidence at
all so far regarding which reciprocating varieties are most help-
ful mutually, and so the only general rule which can be given is
that formulated by Nirody: See that varieties are planted to-
gether which will provide pollen for each other at the time when
each is ready to receive pollen. Fortunately, however, the studies
of Stout enable us to simplify the application of this rule con-
siderably, for he has shown that almost any B variety sheds
pollen at a time of day suitable for almost any A variety to
receive it, and it is only necessary to select varieties not too
widely separated in their season of bloom. Many B varieties
can also be pollinated by almost any A variety, but some of them
open too late in the afternoon for any A variety to be able to
pollinate them certainly. The normal season of bloom for a
number of varieties, as observed by the authors, is given in Fig.
29. It will be noted that there are few varieties whose seasons
are so widely separated that they do not have a few days or
weeks of simultaneous blooming, but it is better not to trust to
brief periods of common bloom. Early varieties ought to have
early or mid-season varieties as reciprocals, and late varieties
should have late or mid-season reciprocating varieties. The fol-
lowing classification may be of assistance.

68 Florida Agricultural Experiment Station

Early Blooming Mid-season Blooming Late Blooming
Fuchsia Collinson Booths 3, 7 and 8
Fuerte Lula Eagle Rock
Gottfried Tonnage Itzamna
Pollock Trapp Linda
Simmonds Wagner McDonald
Waldin Schmidt
Winslowson Taylor

FUERTE _--_ ________

'FUCHS____ _____
uINSLOW5 _____0_ __ ______ _______
WALDIN_____ ___
LINDA ____" ___ZZ _-_______

BoorH # 3
Fig. 29.-Normal blooming season for various varieties of avocados.

The method by which adequate pollination is to be assured in
planting a grove is not wholly established, but the considerable
data amassed at the Sub-Tropical Experiment Station show that
alternating several rows of one variety with an equal number
of one from the reciprocating group provides quite adequate
opportunities for pollination.
In Table 8 is given a scheme of interplanting which combines
the greatest possible number of chances theoretically for cross-
pollination with a fair degree of grove convenience. Diagonal
rows are one variety only, and yet each tree has two reciprocating

Avocado Production in Florida 69

varieties next to it and a third rather close by. This plan is
based on the supposition that three varieties each of A and B
groups are to be planted, but it is readily adaptable to a smaller
number. This satisfies the theoretical considerations for a safe
method of assuring sufficient cross-pollination, but it is not con-
sidered very practical. In this and the succeeding figures of this
section, A and B indicate flower-behavior groups, and the sub-
script numerals indicate any desired varieties. For instance,
A,, A2 and A3 may be Simmonds, Collinson and Waldin, respec-
tively, while B1, B2 and B3 are Trapp, Pollock and Winslowson.

A1 B1 A2 B2 A3 B3 A1 B1 A2 B2 A3 B3
Ba A1 B1 A2 B2 A3 B3 A1 B1 A2 B2 As
As B3 A, BI A2 B2 A3 B3 A1 Bi A2 B2
B2 As B3 A1 B1 A2 B2 A3 B3 A1 B1 A2
A2 B2 A3 B3 A1 B1 A2 B2 A3 B3 A1 B,

B1 A2 B2 A3 B3 A1 B1 A2 B2 A3 B3 A1

A1 B1 A2 B2 A3 B3 Ai Bi A2 B2 A 1 B3
B3 A1 B1 A2 B2 A3 B3 A1 B1 A2 B2 A3
As BS A1 B1 A2 B2 A3 B3 A1 B1 A2 B2
B2 A8 B3 A1 B1 A2 B2 A3 Ba A, B1 A2
A2 B1 A3 B3 A1 B1 A2 B2 As B3 At B1
B1 A2 B2 A3 B3 A1 B1 A2 B2 As B3 A1

Table 9 offers a planting plan which is believed to be quite
satisfactory for assuring cross-pollination and yet offers the
maximum of convenience in grove handling. A wide middle is
left every six rows for a roadway, and the three rows on either
side of it are the same variety. Thus picking and spraying are
done uniformly for any roadway, and yet reciprocating varieties
are never more than three rows from any tree. This scheme of
planting is recommended as quite practical.

70 Florida Agricultural Experiment Station


A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

A, A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B1 BI Bi B1 B1 B1 B1 B1 B1 B1 B1 B1

B1 BI Bi B1 B1 B1 Bi B1 B1 B1 B1 B1

B, Bi B1 B1 B1 Bi B B1 B1 B1 B1 B1

B1 B, Bi Bi Bi Bi Bi B1 Bi B1 BP B1

B1 B1 Bi Bi BI Bi B1 Bi B1 Bi B1 B1

B1 Bi BI Bi Bi Bi Bi Bi B1 B1 B1 B1

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

B3 Bs B3 B, Ba B s B3 B2 B2 B s Bs B

B3 B, B8 B3 B2 Bs B3 B, B3 Bg Bg B3

Bs B2 B3 B2 B, B3 B2 B- B3 B2 B2 B.

Avocado Production in Florida 71

Table 10 suggests a planting scheme intermediate between
the other two, both as to theoretical pollination assurance and
as to convenience of grove handling.


A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B1 Bi B1 B1 B1 B1 B1 Bi Bi Bi BI Bi
Ai A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B1 B Bi B1 B1 B, B1 B, B1 B1 B1 B1

Ai A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B1 BI Bi Bi Bi Bi Bi Bi Bi Bi Bi Bi

A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2
A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2
A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A,

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2

A1 A1 A1 A, A1 A1 A1 A, A1 A1 A1 A1

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2
A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2

A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1 A1

B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2 B2

For those who are contemplating the planting of large acreages,
it is urged strongly that they give careful consideration to the
opportunity afforded them for finding out whether some com-
binations of varieties give greater fruitfulness than others.
There may be compatibilities between certain avocado varieties,
such as are well known for apples and some other fruits, so that
one variety is more satisfactory as a pollinator for certain other

72 Florida Agricultural Experiment Station

varieties than another one is; or, more often, certain varieties
may be poor pollinators for some or all varieties. It may not be
sufficient to provide pollen, if the pollen of some varieties does
not effect fertilization satisfactorily on some other varieties. No
such condition is known for avocados yet.
The planter of a large acreage can plant in 5-acre units, using
only two varieties to the block and interplanting as in either the
second or the third scheme. In a 40-acre tract, he could make
eight such combinations, and with such large units of planting
any difference in pollination compatibility ought to be strikingly
apparent in crop yields. A few hundred acres planted judiciously
would answer positively all questions as to the varieties best
suited for interplanting, and yet the grove owner would be taking
no greater risk in laying out plantings on this basis than he does
at present with any current method of planting.

Fig. 30.-Planting gauge in use.

Planting.-On the limerock soils of Dade County, the practice
is to set the trees higher than in other sections. They are planted
in a mound so that the crown roots are about 6 inches above
the general ground level. The improvised planting gauge shown
in Fig. 30 is made of light 1"x1/s" wood and will be found very
useful by those not accustomed to this type of planting. When

Avocado Production in Florida 73

boxed trees are being set out, the bottom of the box is removed
and the tree set in place in line with the sighting stake. The
soil is packed firmly around it, the sides of the box split with a
hatchet and pulled out, and the tree watered well. A basin
should be made about the tree to hold water and should be
mulched heavily with grass and weeds or sawdust to prevent
drying out and heating of the soil about the new roots. This
mulch should be pulled away, however, when there is danger
of frost, unless the tree is to be covered as frost protection, for
young trees with a mulch, or with weeds growing around the
base, are more readily injured by frost than those around which
the soil is bare.
Trees dug in the field nursery and transported directly to the
grove for setting out, either with bare roots or balled, are planted
to the same depth as are boxed trees. More care must be exer-
cised in filling in the dirt about their roots, however, and it is
well to pour in water while firming the soil about them. Balled
trees should be partially defoliated several days before digging,
either by pulling off most of the leaves or by cutting off about
two-thirds of each leaf. The latter method seems very satis-
factory in practice and gives less chance for sunburn of the limbs.
The trees should be watered liberally several hours prior to dig-
ging, and the ball of roots and dirt enclosed, at once after digging,
in a piece of burlap. They may be loaded on a truck as dug and
wrapped, and when bedded there in moist sawdust they may be
transported long distances. The roots are never exposed to
drying conditions and the trees start readily when planted.
Somewhat older nursery trees are planted with bare roots, but
in this case the branches are cut back severely and buds allowed
to develop from mature wood. Such trees cannot be shipped as
far as balled trees or boxed trees, although, when bedded in wet
sawdust, they can be transported for several hundred miles.
Frequent waterings are necessary until the trees have estab-
lished themselves, and if rainfall does not keep the trees ade-
quately supplied, water must be provided from barrels or tanks.
Four gallons of water per tree should be assured for every three
or four day period during the first two weeks, and thereafter
for two or three months this amount per tree should be given
weekly. One inch of rain will probably give the tree the equiva-
lent of this amount, and whenever a week has passed since more
than an inch of rain has fallen, the trees should be watered
according to need. With a thick mulch the loss of water is less
rapid than in its absence, and these recommendations assume

74 Florida Agricultural Experiment Station

a fair amount of mulch around the tree. By the end of three
months the trees should be able to take care of themselves,
especially if well mulched, unless a long dry period is encountered
during the first year.
Shading of newly planted trees is desirable when plantings are
made at any season, but especially so for plantings in summer.
The most economical and convenient method of shading is to
drive a stake on the south side of the tree, just clearing the
branch spread, and a similar stake on the east and west sides.
A burlap feed or fertilizer sack is split down one side and
stretched in V-form around these three stakes, which should
stand about 4 ft. high. These shades give some protection from
wind as well as from sun.
Culture and Mulching.-On sandy soils, clean cultivation is
usually given during the dry season, followed by cover crops
in the middles during the summer rainy season. On the lime-
rock soils of Dade County, however, such cultural practice is
both difficult and unwise. The usual practice is to permit a
volunteer growth of weeds and grasses to flourish throughout
the rainy season, mowing it at intervals to facilitate grove opera-
tions, and keeping this growth mowed close during the drier
winter and spring. Where permanent cover crops can be estab-
lished they are handled in the same way as the weeds and grass.
Dragging or disking the land need never be done after the initial
scarification, except as preparation for sowing cover crops and
as fire protection. Because the shallow soil necessitates the roots
feeding near the surface, it is unwise to drag a grove at all after
the trees reach size enough that the roots occupy the middles,
although sometimes fire hazards may make it advisable to drag
a few rows.
Most of the soils on which avocados are grown in Florida are
deficient in humus, the only exceptions being those of the Lake
Okeechobee region, and some practice should be followed which
will add organic matter to the soil. In some groves on both sand
and limerock soils the practice of permanent mulching is fol-
lowed with excellent results. The grass and weeds growing in
the row middles are piled about the trees to shade the roots and
conserve moisture, but unless the middles are fertilized also for
the definite purpose of producing a heavy mulch, it is rarely
that enough material can be produced in the grove itself. It is
highly desirable to bring in large quantities of mulching materi-
als from any available outside sources. Where this plan is fol-
lowed, the feeding roots grow into and just beneath the mulch,

Avocado Production in Florida 75

and as it decays more must be added so that the roots will not
be injured by exposure to drying conditions. Mulching is of
extreme importance in the growing of avocados in warm, humid
climates, and particularly so when the soils are as light and
shallow as are those of southern Florida.
Cover Crops.-Leguminous cover crops, or green manures, are
of particular value in that they add nitrogen as well as humus
to the soil, and so reduce the cost of fertilizers. The main factors
to consider in a cover crop are (1) adaptability to local condi-
tions; (2) yield of green matter produced, and (3) ease of
handling the growth produced. A number of cover crops satisfy
these criteria well for the sandy soils of the central part of the
state, where they can be replanted each spring economically,
but, to date, no satisfactory permanent leguminous cover crop
has been found for Dade County, despite several years of effort.
Many cover crops make satisfactory tonnage, but they are either
unable to compete with the volunteer cover crops after the first
season, or they cannot be handled satisfactorily for grove culture,
and the nature of the soil makes it impossible to replant annually.
Two species of Crotalaria (Crotalaria spectabilis and C.
striata) are being grown as green manures rather generally
throughout the state, and have proven more satisfactory than
any other cover crops. The former is somewhat the more de-
sirable of the two. Bunch velvet beans, cowpeas, beggarweed,
soybeans, and other crops may be grown in sections where they
give satisfactory growth. No cover crop makes a better growth
on newly scarified pineland in the Redland district than Crota-
laria spectabilis. The seed may be sown at any time during the
winter and allowed to germinate with the spring rains. An
application of 500 lbs. per acre of acid phosphate soon after the
seedlings appear is highly beneficial for this or any other cover
crop on the limerock soil, but on the sandy soils a complete fer-
tilizer analyzing 4-8-3 or of similar analysis should be applied
in like amount.
Most cover crop seeds should not be sown until the spring
rains make germination sure. In preparing the ground, it is
well to harrow or drag it very thoroughly in order to kill out as
much as possible of the grass and weeds and prevent their com-
peting with the young cover crop plants. It is also advisable to
sow a somewhat larger quantity of seed than is generally recom-
mended, because of the persistence and rapidity of growth of
volunteer weeds at this season. The seed is sown broadcast
usually, and lightly harrowed in.

76 Florida Agricultural Experiment Station

Where a winter tomato crop is planted in the row middles the
first season, it should be followed by Crotalaria or soybeans,
which will produce several tons of green matter. Crotalaria is
able to volunteer successfully year after year only if the ground
is dragged each spring to cover the seed and reduce weed com-
petition. This dragging is not recommended after the first few
years because of the spread of the tree roots to the middles.
Natal grass offers, for the present, the best permanent cover
crop for southern Dade County, and if given a good start and
allowed a little plant food for itself, it makes a good supply of
mulch annually without having the disagreeable features of some
common weeds.
Pruning.-No systematic pruning methods for the avocado
are generally followed. Trees which have been well. cared for
and have never suffered a set-back require little pruning. Some-
times, with certain varieties, small limbs which have carried a
very heavy crop are devitalized, and these should be cut back
to strong healthy growth. Limbs resting on the ground should
be removed if they interfere with mowing and other cultural
operations. Fruit on such limbs is sometimes scarred and
bruised, and it is more likely to be eaten by rats and other
animals. Some varieties, especially Lula and Taylor, tend to
grow very tall, and these should be pinched back periodically
while young to encourage a more spreading habit. Low, spread-
ing trees are more economically handled in spraying, pruning,
picking and other cultural operations and are less liable to wind
damage. Dead, broken or diseased limbs should be removed, the
cuts being made close to the limbs from which these branches
The best time to prune is in the dormant period of winter
after the fruit has been picked, if it matures in the fall or early
winter. All exposed surfaces should be painted with some
protective material soon after the cuts are made. Carbolineum
and several commercial pruning paints having an asphalt base
have been found very satisfactory for this work. When cuts
are left unpainted, wood borers are sometimes found deep in the
pith. These insects gradually burrow downward and weaken
the limb to such an extent that it rarely recovers, and wood-
decaying fungi follow them.
Fertilization.-In the early days of avocado growing in Florida
the trees were generally fertilized with the same mixtures and
in approximately the same amounts as were citrus trees. It
became evident, however, that the requirements of the two in

Avocado Production in Florida 77

respect to fertilization differed somewhat, and separate formulas
and analyses for avocados were tried. From these trials a scheme
of fertilization of avocados has been developed which differs
from that used for citrus in the greater quantities used, the
higher percentage of ammonia in theanalysis, and the derivation
of a greater proportion of the ammonia from organic sources.
These points of difference, if not universally accepted, are the
basis upon which most avocado fertilizer mixtures are made.
The formulas used by different growers vary considerably and
good results have been obtained under widely varying treat-
ments, providing the quantity used was sufficient. Animal and
poultry manures are very beneficial to the avocado, adding humus
and bacteria to the soil besides being valuable as fertilizers.
In the absence of experimental data no definite and specific
information can be given. The following practices are based on
the experience and observations of successful growers. Newly
planted trees receive 1 lb. per tree of a mixture analyzing ap-
proximately 5-7-2*, the ammonia being derived chiefly from
organic materials. This application is made from 3 to 4 weeks
after planting. Following this, the same amount of similar
analysis is given at intervals of about 60 days during the first
year. Cottonseed meal or tankage in the same amount is
often substituted during the summer rainy season. In the second
year the same analysis is used but the total quantity is ap-
proximately double that for the first year. The number of
applications per year is reduced to three after this time, usually
made in February, June and October, although some growers
split the summer application because of leaching during the
heavy rains of this season. The amounts applied are increased
annually. Five year old trees of average size receive 8 to 10 lbs.
per application and older trees are fertilized according to size
and age. The percentage of potash used in the mixture is
usually increased as the trees come into bearing, especially in
the summer and fall applications. Trees of fruiting age are
usually fertilized in the spring with a 5-8-3 or 6-6-3 mixture,
and in the fall with 4-8-10, while the summer application is
likely to be 4-7-5 or 5-5-5.
The tolerance of the avocado tree to extreme conditions of
soil acidity and alkalinity has not been thoroughly investigated.
Where the soil is known to be far from average in reaction, the
safer plan is to use, so far as possible, materials which will tend
to bring about a more nearly normal soil reaction. Sulphate of
5% ammonia, 7% available phosphoric acid, 2% potash.

78 Florida Agricultural Experiment Station

ammonia and most of the organic ammoniates will aid in cor-
recting highly alkaline soils, while nitrate of soda, bone meal,
basic slag and lime tend to neutralize acid soils.
Under Florida conditions the avocado may receive large
amounts of nitrogenous fertilizer without apparent injury to
the tree. In common with most fruits, however, a vigorous
growth and a fruitful habit do not exist at the same time in
the same tree. A check in growth must take place before the
tree will become fruitful. The higher percentage of potash in
the fall application of fertilizer is usually employed with the
idea of achieving this result, although such experiments as have
been carried out lend no encouragement to the hypothesis.
Tree condition should be considered in determining the kind
and quantity of fertilizer to be used, and the mistake should
not be made of allowing trees to suffer for lack of sufficient
fertilizer for normal development. Under-nourished trees pro-
duce fruit which is sub-normal in size and pale in color and is
generally lacking in attractiveness. If considerable variation
is apparent in the grove, the trees should be divided into two
classes with respect to condition of growth and fertilized ac-
Special attention must be given to the fertilization of trees
carrying heavy crops of fruit. If they are allowed to become
undernourished, there is danger of shedding much of their foliage
and fruit when fertilizer again becomes available. A very heavy
bloom is also quite a drain on the resources of the tree and should
be compensated. When an unusually heavy crop has been set,
it is well to make one or more light applications of ammonia
intermediate to the regular ones, so that the tree never has an
opportunity to suffer from hunger. Kept in vigorous growing
condition, with full foliage, the tree matures its fruit without
injury to itself and without sun-burning and dwarfing of the
fruit. Trees which fail to set a crop need not be fertilized nearly
so heavily as those loaded with fruit, and need only be kept in
good healthy condition for the next year's crop.
Windbreaks.-In the areas where avocados are grown com-
mercially in Florida, winds are prevalent and cause more or less
injury to tree and crop. One is prone to think first of the occa-
sional winds of hurricane force, but these are not really so im-
portant a factor as the ordinary sea breezes, because the former
come at infrequent intervals. During the dry season the winds
cause an additional tax on the water-obtaining power of the tree
by increasing evaporation losses, and this may result in heavy

Avocado Production in Florida 79

dropping of immature fruit. The leaf of the avocado is stiff
enough in structure so that it never shows water deficit by wilt-
ing, as citrus leaves do, but the rapid shedding of fruit when
rains come again, if not sooner, shows that the deficit has been
felt keenly. Windbreaks reduce air movement and so lower
evaporation loss. Another factor of great importance is the
injury of fruits through rubbing against branches or against
each other. If bruised, a source of entry for fungi is afforded,
and if only scarred, the fruit is spoiled in appearance. During
high winds there is danger of the breakage of limbs heavily
loaded with fruit. These mishaps are greatly reduced by good
While a single row of windbreak trees affords some protection,
it is highly desirable to plant at least a double row in staggered
formation. The windbreak should extend clear around the
grove, and when the grove is larger than five acres, it is well to
separate each tract of five acres from the next by a single or
double line of windbreaks. The space sacrificed for windbreak
purposes will be a valuable investment in improved fruit. Where
the contour of the land is uneven, as in the Ridge section, open-
ings in the windbreaks should be left at one or more of the lowest
places to permit drainage of cold air out of the grove.
The selection of windbreak species should be based on the
following considerations: (1) Rate of growth; (2) ultimate size
reached; (3) resistance offered to wind; (4) toughness of
branches; (5) root habits, and (6) adaptation to soil and climate.
Some species of Ficus would make excellent windbreaks were it
not for their undesirable root spread. Other trees are easily
broken up by the wind, or grow too slowly to be serviceable for
grove protection. No trees have shown themselves more satis-
factory as windbreaks in southern Florida than the Casuarinas.
In Dade County there are two species commonly grown, the tall,
slender "Australian pine" and the shorter, thicker "Brazilian
oak". These species have been considered provisionally as Casu-
arina equisetifolia and C. lepidophloia, respectively, although
the correctness of this taxonomy is in doubt. Both species give
very good protection against wind, are rapid in growth, and
become tall enough to be effective windguards. Furthermore,
they both have nitrogen-fixing bacteria in their root nodules, as
Mowry (11) has shown, and so they enrich the soil somewhat.
The second species tends to produce root suckers on the limerock
soil when the roots are injured by dragging. It makes a lower
and denser growth than the other species and is a better wind

80 Florida Agricultural Experiment Station

protection. Both species grow well along along the East Coast
and on the muck soils of the Everglades section.
Other satisfactory windbreak species are the Australian silk-
oak (Grevillea robusta) in the Ridge section and the Woman's-
tongue (Albizzia lebbek) in Dade County. The species of Euca-
lyptus have in general not made satisfactory windbreaks in
Florida. Many other trees are on trial for windbreaks at the
Sub-Tropical Experiment Station and elsewhere, but they have
not been tried sufficiently to be either recommended or rejected.
Rejuvenation of Neglected Groves.-Trees, abandoned or
neglected for some time, may be brought back to a fruitful
condition if reasonably sound in roots, trunk and larger limbs.
Each tree should be examined carefully, and those which have
become stunted on account of being loose in the ground should
be replaced with nursery trees. Drastic cutting back of tops
and the application of a mixed fertilizer such as is used on young
trees are the two most important remedial measures. The trunk
and limbs should be examined for decayed places. Wherever
the bark has been broken, wood-rotting fungi and borers are
almost sure to enter and begin their destructive work. Green
avocado wood is comparatively soft and decays rapidly, and
diseased areas must be treated before the decay has penetrated
deeply. All diseased tissues should be cut away and the exposed
surfaces treated as described under "Pruning". It is important
that the cuts be made in such a way that they will not collect
and hold water. If the decay has extended downward inside
farther than outside, a hole may be bored upward through the
bark and wood to the bottom of the pocket. A small opening of
this kind will provide drainage without the necessity of weaken-
ing the trunk or limb by excessive cutting. The hole may need
to be opened again later if it has healed over before the large
wound has.
If insect pests or fungus diseases are present, control measures
should be started as indicated in the discussion of these organ-
isms. Top-working of unsatisfactory varieties in the planting
may be done as described under "Propagation". The opportunity
is a good one to revise the grove planting scheme, if necessary,
to allow better facilities for proper pollination by top-working
or replacement with nursery trees. In addition to the remedial
measures described above, the grove should be mowed and
mulched well. Subsequent care should be as for any other plant-
ings, except that the trees should not be allowed to carry a heavy
crop the first season.

Avocado Production in Florida 81

Yields.--Seedling avocados as a rule come into bearing much
later than budded trees, from 5 to 7 years being required usually.
Budded trees frequently bear one or two fruits the year after
being planted, and one or two precocious varieties may fruit
in the nursery row. Usually, however, no fruits are borne the
first year, and those produced should be removed as soon as they
are noted, since carrying a crop at this age may seriously retard
the development of the tree. Any fruit set the second year also
should be removed, but by the third year the budded tree should
be able to set and mature a crop of small size, and by the fourth
year it should carry a good crop safely.
Accurate yield data, extending over several normal seasons,
are not available for most varieties of avocados. The yield varies
tremendously from one season to the next, partly depending on
the size of crop carried the previous year, partly determined by
the conditions at the blooming season, and partly governed by
the rainfall and winds during fruit development. Following the
infrequent hurricanes, trees on the lower East Coast may require
several years to come back into normal condition. Basing esti-
mates on exceptional specimen trees or on one or two unusually
good seasons for a fine grove, yield probabilities have sometimes
been placed ridiculously high. Even such heavy and consistent
bearers as Trapp and Waldin cannot be expected to produce
more than two 40-lb. crates of fruit per season, as the average
over a period of years, although occasionally such trees may
produce more than 10 crates. A safer expectancy for long time
production would be one crate per tree. Lula, Collinson, Taylor,
Wagner and Linda may be counted on for an average production
of about one crate also, while Winslowson, Fuchsia and Simmonds
will average a little below this figure, and varieties like Pollock,
Schmidt and Taft will not average 10 fruit per tree in commer-
cial groves over a long period of years. The new hybrids have
not been grown in commercial grove form long enough to make
estimates of production have any value, although these hybrids
give promise of being reasonably prolific.
Thinning.-Most varieties of avocados tend in greater or less
degree toward alternate bearing, i.e., a heavy crop one season
is followed by a light crop or none at all the next year. Some
varieties are more pronounced in their expression of this ten-
dency than are others. While it seems to be a natural tendency
for the species, it is highly probable that proper thinning of the

82 Florida Agricultural Experiment Station

crop would in large measure bring about more regular bearing.
This practice has long been recognized as practical and desirable
for some other fruits, such as apples and peaches, and it is
believed that it would prove equally desirable for avocados. A
large portion of the crop is shed naturally in separated periods
of dropping fruit, but this varies with the seasonal conditions
and cannot be relied upon to relieve an overburdened tree suf-
ficiently. So far as is known no one has ever practiced avocado
thinning extensively, and so there is no basis of experience for
making suggestions. In the absence of such experience, the
following suggestions are offered, derived from experience with
other fruits.
The best time for the first thinning is when the fruit is about
one inch in diameter. Heavily laden trees and early maturing
varieties should receive attention first. The number of fruits to
be removed must be determined by the grower, and should be
governed by the condition of the particular tree and the ability
of the variety to carry heavy crops. All fruit which is badly
blemished, bruised or misshapen should be removed first, since
such fruit would be of little value even if the tree could mature
it, and the food and moisture which it would use may better go
to develop better quality fruit. Small branches carrying very
heavy loads of fruit should be relieved of much of it. Such
branches rarely are able to produce the normal amount of foliage,
and the fruit is likely to be dwarfed and sunburned if not thinned
radically. Six or eight weeks later a check-up should be made,
and additional fruit removed where necessary.
Picking.-Avocados should be picked with orange clippers,
cutting the stem close to the fruit so as to avoid stem punctures
of other fruit. The avocado is very susceptible to decay when
the skin has been broken, and careful handling at all times will
prevent the loss of much fruit from this cause. For reaching
fruit in the top of tall trees, a long bamboo picking pole is used.
To the end of the pole is attached a sharp-bladed hook, and below
this is fastened a small canvas bag to catch the cut fruit. The
picker carries a galvanized iron picking bucket with a layer of
excelsior at the bottom to receive the fruit on transfer from the
picking pole receptacle, or to pick fruit into directly by hand
clipping, and these buckets have their contents in turn placed
in field crates well padded with some soft material on the bottom
and sides. In these padded field crates the fruit is delivered
to the packing shed.

Avocado Production in Florida 83

The most difficult phase of picking avocados is to know when
they are ready to pick. The season of maturity varies slightly
from year to year for each variety, according to the time of
bloom and the seasonal conditions during fruit growth, and so
no calendar date can be given for maturity of any variety. In
order to create a market and maintain the demand necessary
for the profitable culture of a little known fruit such as the
avocado, it is imperative that the consumer be offered fruit
which has attained its full flavor and maturity. The avocado
can be popularized on its merits, but unripe fruit has no merit
and is only distasteful. Due to the similarity in external ap-
pearance of mature and immature fruits, it is usually impossible
for the purchaser to differentiate between them, and the result
is too often disappointment and prejudice against the avocado.
Unlike some fruits, the avocado remains in perfect condition
on the tree for sometime after reaching maturity, a few fruit
often hanging on for months, and never becomes soft enough
on the tree for eating. Before the first picking is made, several
fruits should be laid aside for a week to see if they will soften
properly and possess the normal flavor of the variety. If the
samples taken become tough and rubbery and begin to shrivel,
they have not yet reached the proper degree of maturity and
picking should be delayed until such a stage is reached. The
dropping of the first sound fruits when approximately full sized
is usually taken as an indication that the fruit is mature. When
combined with the ripening test, this affords a fairly dependable
determination of maturity, but care must be exercised to see
that the fruit has not dropped because of fungus infection of
the stem. Until such time as a relatively simple and accurate
test of maturity can be standardized, the ripening test should
be used in determining whether fruit is ready to pick and ship.
In the case of over-ripe fruit, the consumer can usually judge
its condition readily by the decayed or discolored skin and the
mushy consistency. The picking and shipping of fruit which
has reached the fullest possible degree of maturity on the tree
is not recommended, but it is much preferable to shipping im-
mature fruit. Such exceptionally mature fruit, if graded care-
fully, may be marketed successfully when packed in iced crates
and shipped to consuming centers, and its quality is splendid if
the fruit is firm on arrival.
When the fruit is adjudged mature, the first pickings from
the more heavily loaded limbs should consist of all but the very
small fruits. Unless this is done, the loss of vitality occasioned

84 Florida Agricultural Experiment Station

by the overcrop may induce a dying back of such branches and
the consequent loss of all the fruit borne on them. Of course,
if the fruit has been thinned judiciously, this situation will not
arise at harvesting. From parts of the tree when the fruit is
well distributed, the practice should be followed of picking the
largest fruit each time.

A -S '

Fig. 31.-Avocados packed in excelsior for shipment.

Packing.-Florida avocados are packed for shipment in three
kinds of containers: The "vent" crate, the iced crate, and the
lug. The last container is used for the great bulk of the crop.
The ventilated or "vent" crate is the standard tomato crate and
holds 40 pounds of fruit. The iced crate is used for long distance
shipments in hot weather and for very mature fruit. There are
two types in use. In one, the ice compartment is in the center
and holds about 12 pounds of ice; in the other, the ice compart-
ment is above the fruit, extending over the entire pack, and holds
about 20 pounds of ice. The commonly used lug holds approxi-
mately 15 pounds of fruit and has inside dimensions as follows:
Length 15", width 13", and depth 31/4", 33/4" or 41/4", to allow
for different sizes of avocados.

Avocado Production in Florida 85

In packing avocados, layers of excelsior or wood wool are
placed on all the inside surfaces of the package, as well as be-
tween the fruits, so that each fruit is "nested". (Fig. 31.) The
bulge pack used for citrus is quite impracticable for avocados,
as they have no resiliency and cannot withstand pressure without
injury. The use of tissue wraps for avocados is also undesirable,
as wrapped fruit tends to ripen too quickly. The pack, or number
of fruits per lug, varies with the variety and also within the
variety. The normal range for each variety is given under the
varietal description.
Marketing.-In past years the bulk of the avocado crop has
moved to market by express train and boat, mostly to Northern
markets. New York, Chicago, Washington, Boston, St. Louis
and Cleveland receive the largest shipments, in the order of
naming. In the last two years, however, there has been a great
increase in the amount of fruit carried by motor trucks, owing
to the constantly improving system of state and federal high-
ways, and the volume carried by trucks bids fair to equal or
excel that carried by older transport forms. The newer trans-
portation vehicles have greatly increased the range of distribu-
tion of avocados and have opened many new markets all through
the South and East.
Prior to 1928 the crop was marketed either by fruit buyers
or by the individual growers through private customers and
commission houses. In 1928 the Florida Avocado Growers Ex-
change was organized as a cooperative marketing agency com-
posed of South Florida growers, and headquarters and packing-
house were established at Naranja, near Homestead. A good
portion of Florida avocados now goes to market through this
medium. The fruit handled by the Exchange is marketed under
the trade name "Flavocado". Four grades have been established,
ranging from Blue, the highest, through Red and Yellow to
Black. This last grade is not sold under the "Flavocado" label,
and most of such fruit is sold in bulk at the packinghouse and
disposed of on the Miami market. The variety name is stamped
on each lug shipped, except that seedlings and minor varieties
are marked "Assorted".
The preference of consumers with regard to size, color and
texture of fruit varies widely in different markets and with
fluctuating price levels. Considerable experience in marketing
the avocado and constant contact with the principal markets are
necessary in order that maximum returns may be obtained by
the shipper. The general tendency of the trade, however, seems

86 Florida Agricultural Experiment Station

to be toward fruit of small to medium size, green in color, and
fairly smooth-skinned or pebbled.

This disease attacks the leaves, bark and fruit. On the fruit,
where it is most commonly found, it is known as "black spot".
The organism (Colletotrichum sp.) enters the fruit through
breaks in the skin and forms dark, sunken spots, usually circular
in outline. The infection may penetrate into the flesh of the
fruit, causing decay which may spread widely through the fruit.
The fungus sometimes attacks branches, killing the growth back
from the tip and spreading down until it may cause the death
of the whole tree. The affected twigs have their bark turned
black, and the wood underneath is also discolored. Usually
when a tree is attacked and has become badly affected, the sur-
rounding trees will begin to show the disease in a short time.
Control.-Anthracnose can be controlled on the fruit by timely
applications of bordeaux spray, as Stevens (21) has demonstrat-
ed. Three applications of 3-3-50 bordeaux are recommended, as
follows: (1) Three weeks after the fruit has set; (2) four weeks
later; and (3), three or four weeks after the second. Fresh
stone lime should be used in making up the spray mixture.
When branch infections are noticed, the infected parts of the
tree should be cut off and burned. Care should be taken to cut
back to clean, healthy tissue. The affected tree and those adja-
cent to it should be sprayed with 3-3-50 bordeaux. Keeping
trees in a healthy growing condition will largely prevent occur-
rence of the disease in branches. Places where the bark has
cracked open as the result of sun-burning or other injury afford
easy entrance for the organism. Dropped fruit which is affected
with the disease and the diseased twigs afford sources of infec-
tion for other fruit and twigs, and should be removed.
Blotch is a disease of the fruit which Stevens has described.
It resembles black-spot somewhat, but the spots differ in being
irregular in outline, only slightly sunken, and never penetrating
into the flesh. In itself the disease only spoils the appearance
of the fruit, although it may open up an entrance for other
fungi to enter and cause fruit decay, especially for the anthrac-
nose fungus. The blotch organism (Cercospora sp.) requires

86 Florida Agricultural Experiment Station

to be toward fruit of small to medium size, green in color, and
fairly smooth-skinned or pebbled.

This disease attacks the leaves, bark and fruit. On the fruit,
where it is most commonly found, it is known as "black spot".
The organism (Colletotrichum sp.) enters the fruit through
breaks in the skin and forms dark, sunken spots, usually circular
in outline. The infection may penetrate into the flesh of the
fruit, causing decay which may spread widely through the fruit.
The fungus sometimes attacks branches, killing the growth back
from the tip and spreading down until it may cause the death
of the whole tree. The affected twigs have their bark turned
black, and the wood underneath is also discolored. Usually
when a tree is attacked and has become badly affected, the sur-
rounding trees will begin to show the disease in a short time.
Control.-Anthracnose can be controlled on the fruit by timely
applications of bordeaux spray, as Stevens (21) has demonstrat-
ed. Three applications of 3-3-50 bordeaux are recommended, as
follows: (1) Three weeks after the fruit has set; (2) four weeks
later; and (3), three or four weeks after the second. Fresh
stone lime should be used in making up the spray mixture.
When branch infections are noticed, the infected parts of the
tree should be cut off and burned. Care should be taken to cut
back to clean, healthy tissue. The affected tree and those adja-
cent to it should be sprayed with 3-3-50 bordeaux. Keeping
trees in a healthy growing condition will largely prevent occur-
rence of the disease in branches. Places where the bark has
cracked open as the result of sun-burning or other injury afford
easy entrance for the organism. Dropped fruit which is affected
with the disease and the diseased twigs afford sources of infec-
tion for other fruit and twigs, and should be removed.
Blotch is a disease of the fruit which Stevens has described.
It resembles black-spot somewhat, but the spots differ in being
irregular in outline, only slightly sunken, and never penetrating
into the flesh. In itself the disease only spoils the appearance
of the fruit, although it may open up an entrance for other
fungi to enter and cause fruit decay, especially for the anthrac-
nose fungus. The blotch organism (Cercospora sp.) requires

Avocado Production in Florida 87

no break in the skin in order to effect entrance, as the black spot
organism does.
Control.-The spraying recommended for black spot control
will also control blotch satisfactorily.
Different varieties of avocado differ greatly in their suscepti-
bility to this disease, which is closely related to citrus scab.
The Collinson is one of the most resistant varieties, and Lula
one of the most susceptible. The scab organism (Sphaceloma
sp.) attacks the young foliage and young fruit, but it is rarely
a serious trouble on the foliage except in the nursery. The
fruit of some varieties, however, may be almost entirely of cull
grade because of the degree of scabbiness. The spots on the
fruit are irregular in outline, but often coalesce into a large
irregular area which gives the fruit a russetted appearance.
Practically the whole surface of the fruit may be affected in
some cases. The quality of the mature fruit is not in the least
affected by the disease, which is limited to the skin, but the
appearance is made very unattractive and in severe cases the
fruit may be deformed or dwarfed. On young twigs and leaves
the spots become corky in mature stages and cause considerable
distortion of the leaves.
Control.-The extensive studies on scab by Stevens have
shown that it can be controlled on the fruit by proper spraying
with 3-3-50 bordeaux, at least under most conditions. Three
applications should be made, as follows: (1) Just before the
opening of the bloom cluster, especially if the old foliage shows
scab; (2) near the end of the main flush of growth, when the
small fruits are just becoming visible; (3) about three weeks
after the second application. The first or dormant spray may
be omitted if no old scab infections are evident, but its applica-
tion is highly desirable, especially if there has been much scab
on the fruit the previous season. It will be noted that the third
spray for scab control can serve also as the first spray for black
spot and blotch.
Avocado diseases less frequently found are rusty blight
(Gloeosporium sp.) and powdery mildew (Oidium sp.), the
latter being found more often in the nursery than in the grove.
Sun-blotch is a rather new virus disease of avocados in California
which has been observed only once in Florida, on a branch de-
veloping from a California scion. Avocado blast is another

Avocado Production in Florida 87

no break in the skin in order to effect entrance, as the black spot
organism does.
Control.-The spraying recommended for black spot control
will also control blotch satisfactorily.
Different varieties of avocado differ greatly in their suscepti-
bility to this disease, which is closely related to citrus scab.
The Collinson is one of the most resistant varieties, and Lula
one of the most susceptible. The scab organism (Sphaceloma
sp.) attacks the young foliage and young fruit, but it is rarely
a serious trouble on the foliage except in the nursery. The
fruit of some varieties, however, may be almost entirely of cull
grade because of the degree of scabbiness. The spots on the
fruit are irregular in outline, but often coalesce into a large
irregular area which gives the fruit a russetted appearance.
Practically the whole surface of the fruit may be affected in
some cases. The quality of the mature fruit is not in the least
affected by the disease, which is limited to the skin, but the
appearance is made very unattractive and in severe cases the
fruit may be deformed or dwarfed. On young twigs and leaves
the spots become corky in mature stages and cause considerable
distortion of the leaves.
Control.-The extensive studies on scab by Stevens have
shown that it can be controlled on the fruit by proper spraying
with 3-3-50 bordeaux, at least under most conditions. Three
applications should be made, as follows: (1) Just before the
opening of the bloom cluster, especially if the old foliage shows
scab; (2) near the end of the main flush of growth, when the
small fruits are just becoming visible; (3) about three weeks
after the second application. The first or dormant spray may
be omitted if no old scab infections are evident, but its applica-
tion is highly desirable, especially if there has been much scab
on the fruit the previous season. It will be noted that the third
spray for scab control can serve also as the first spray for black
spot and blotch.
Avocado diseases less frequently found are rusty blight
(Gloeosporium sp.) and powdery mildew (Oidium sp.), the
latter being found more often in the nursery than in the grove.
Sun-blotch is a rather new virus disease of avocados in California
which has been observed only once in Florida, on a branch de-
veloping from a California scion. Avocado blast is another

88 Florida Agricultural Experiment Station

California disease of avocados which has not been reported
from Florida. It is caused by Bacterium citriputeale, which
causes blast of citrus fruits. The blight and mildew can be
controlled by spraying with 3-3-50 bordeaux when they appear.
There are a number of troubles afflicting the avocado and
finding expression in an unhealthy or diseased appearance of
the foliage which are apparently due wholly to conditions under
which the tree is growing. The tree condition known variously
as "rosetting", "frenching" or chlorosiss" is one of these. While
the symptoms are not always well defined, in general the leaves
which appear become curled, yellowed and dwarfed, and some-
times a dying back of new growth follows. Nothing definite
is known as to the cause of this rather infrequent trouble, and
investigation is needed to determine the cause and corrective
measures. It has been observed, however, that trees growing
in soil well supplied with organic matter are rarely affected.
If cases occur in the grove, such trees should be given repeated
heavy mulching and kept well fertilized.
Another apparently physiological disease is "tip-burn", which
affects the leaves of certain varieties of avocados, notably Taylor.
It is characterized by a dying-back of the tip for one-third to
one-half of the length of the leaf, giving a scorched appearance.
The disease usually appears in the fall after the leaves are fully
mature. No serious results have been observed from such a
condition, since affected trees continue to grow and fruit well.
Such leaves would normally soon be shed and replaced by new
growth. There is no reason to believe that spraying would have
any preventive or curative effect.
Trees which have endured a few days of water standing
higher than the crown roots are likely to die back quickly as if
injured by lightning. Development of very small leaves may
follow the application of large quantities of inorganic fertilizers
to trees with consequent burning of feeding roots.

Most of the work on avocado insects has been done by Moznette,
whose bulletin (12) was written in 1922. The reader may refer
to it for a more comprehensive discussion of the insect pests.
The bulletin on citrus insects by Watson (27) gives a full dis-
cussion of methods of preparing various insect sprays, and
should be referred to for information on this matter. However,

Avocado Production in Florida 87

no break in the skin in order to effect entrance, as the black spot
organism does.
Control.-The spraying recommended for black spot control
will also control blotch satisfactorily.
Different varieties of avocado differ greatly in their suscepti-
bility to this disease, which is closely related to citrus scab.
The Collinson is one of the most resistant varieties, and Lula
one of the most susceptible. The scab organism (Sphaceloma
sp.) attacks the young foliage and young fruit, but it is rarely
a serious trouble on the foliage except in the nursery. The
fruit of some varieties, however, may be almost entirely of cull
grade because of the degree of scabbiness. The spots on the
fruit are irregular in outline, but often coalesce into a large
irregular area which gives the fruit a russetted appearance.
Practically the whole surface of the fruit may be affected in
some cases. The quality of the mature fruit is not in the least
affected by the disease, which is limited to the skin, but the
appearance is made very unattractive and in severe cases the
fruit may be deformed or dwarfed. On young twigs and leaves
the spots become corky in mature stages and cause considerable
distortion of the leaves.
Control.-The extensive studies on scab by Stevens have
shown that it can be controlled on the fruit by proper spraying
with 3-3-50 bordeaux, at least under most conditions. Three
applications should be made, as follows: (1) Just before the
opening of the bloom cluster, especially if the old foliage shows
scab; (2) near the end of the main flush of growth, when the
small fruits are just becoming visible; (3) about three weeks
after the second application. The first or dormant spray may
be omitted if no old scab infections are evident, but its applica-
tion is highly desirable, especially if there has been much scab
on the fruit the previous season. It will be noted that the third
spray for scab control can serve also as the first spray for black
spot and blotch.
Avocado diseases less frequently found are rusty blight
(Gloeosporium sp.) and powdery mildew (Oidium sp.), the
latter being found more often in the nursery than in the grove.
Sun-blotch is a rather new virus disease of avocados in California
which has been observed only once in Florida, on a branch de-
veloping from a California scion. Avocado blast is another

88 Florida Agricultural Experiment Station

California disease of avocados which has not been reported
from Florida. It is caused by Bacterium citriputeale, which
causes blast of citrus fruits. The blight and mildew can be
controlled by spraying with 3-3-50 bordeaux when they appear.
There are a number of troubles afflicting the avocado and
finding expression in an unhealthy or diseased appearance of
the foliage which are apparently due wholly to conditions under
which the tree is growing. The tree condition known variously
as "rosetting", "frenching" or chlorosiss" is one of these. While
the symptoms are not always well defined, in general the leaves
which appear become curled, yellowed and dwarfed, and some-
times a dying back of new growth follows. Nothing definite
is known as to the cause of this rather infrequent trouble, and
investigation is needed to determine the cause and corrective
measures. It has been observed, however, that trees growing
in soil well supplied with organic matter are rarely affected.
If cases occur in the grove, such trees should be given repeated
heavy mulching and kept well fertilized.
Another apparently physiological disease is "tip-burn", which
affects the leaves of certain varieties of avocados, notably Taylor.
It is characterized by a dying-back of the tip for one-third to
one-half of the length of the leaf, giving a scorched appearance.
The disease usually appears in the fall after the leaves are fully
mature. No serious results have been observed from such a
condition, since affected trees continue to grow and fruit well.
Such leaves would normally soon be shed and replaced by new
growth. There is no reason to believe that spraying would have
any preventive or curative effect.
Trees which have endured a few days of water standing
higher than the crown roots are likely to die back quickly as if
injured by lightning. Development of very small leaves may
follow the application of large quantities of inorganic fertilizers
to trees with consequent burning of feeding roots.

Most of the work on avocado insects has been done by Moznette,
whose bulletin (12) was written in 1922. The reader may refer
to it for a more comprehensive discussion of the insect pests.
The bulletin on citrus insects by Watson (27) gives a full dis-
cussion of methods of preparing various insect sprays, and
should be referred to for information on this matter. However,

Avocado Production in Florida 89

it should be borne in mind that the avocado will be burned more
readily than citrus trees by oil, and oil emulsions should contain
only 34 of 1% of oil for avocados, where 1% is recommended
for citrus.
In southern Florida this pest (Chrysomphalus dictyospermi
Morgan.) is the most injurious insect attacking the avocado. It
is found in the nursery as well as in the grove. Varieties of the
West Indian race are preferred as hosts, but no variety has been
found immune to its attack in southern Florida. In the grove
the scale is found on twigs, on young vigorous limbs, and occa-
sionally on foliage and fruit. Heavy infestations weaken the
smaller branches and often cause them to die. The first indica-
tion of injury is a cracked and darkened appearance of the green
bark. Trees which are already badly affected and are showing
an unthrifty condition will be found to have the bark almost
concealed by the scales of this pest in the angles where small
branches leave the larger.
The insects are more abundant in the summer and early fall
months, when the trees are carrying a crop. Considerable dam-
age may be done at this season because a drain is already made
upon the tree by the crop and the additional weakening caused
by the insect pest may be more than the tree can stand. The
Trapp is more susceptible to serious injury by this organism
than any other variety, and it has been observed that in groves
of this variety, heavily loaded trees may be badly attacked while
trees carrying little or no crop are uninjured. The insects are
also sometimes found along the fruit stem and at the point where
the stem is attached to the fruit, causing premature dropping
of the fruit. The injury caused by this organism is through
loss of sap which it sucks from the young tissues. The scale
covering is small (about 1/25 inch in diameter) brownish-gray,
circular in outline and nipple-like. In the crawler stage the
insect is yellow.
Control.-Oil emulsions usually are effective in controlling the
dictyospermum scale. Two applications made three weeks
apart are necessary. Since the infestations are lightest in
winter and the cooler weather of this season is less conducive
to spray burn, it is advisable to spray thoroughly in December
or January. If it is found necessary to attempt control during
the summer months, spraying should be done in late afternoons
or on cloudy days.

90 Florida Agricultural Experiment Station

The twice-stabbed lady beetle (Chilocorus bivulnerus Muls.)
feeds upon the dictyospermum scale and has greatly aided in
keeping this pest in check. But it cannot be relied upon for
complete control.
This scale (Protopulvinaria pyriformis Ckll.) is not so de-
structive in Dade County as dictyospermum, but causes a mar-
ring of the fruit appearance due to the sooty-mold fungus
which develops in the honeydew secreted by this insect. In the
northern and central portions of the state it is a serious pest
comparable to dictyospermum in the south. It is found on the
under surface of leaves and occasionally on the fruit, where it
attaches itself and sucks the plant juices. The adult is pear-
shaped, reddish-brown with a white margin, and about 1/8 inch
in length.
Control-Spraying as recommended for dictyospermum scale
will give good control, but special care must be taken to spray
thoroughly the underside of the foliage.
This whitefly (Trialeurodes floridensis Q.) is smaller than
any of those attacking citrus, the adult being less than 1/25
inch in length. The injury caused is very similar to that caused
by pyriform scale. The body of the adult is lemon-yellow. In
the pupa (or resting) stage the insect may readily be identified
by the yellow body covered by a thin transparent membrane,
the circular shape, and the fringed margin.
Control.-Two applications of oil emulsion, the first in Novem-
ber and the second in February, will give satisfactory control.
The insect lives on the under side of the leaves and is more
abundant on the well-protected and shaded parts of the tree.
The spray should, therefore, be directed particularly to these
parts. The papaya, guava, annona and a number of native
plants also are hosts of this insect. When any of these are
growing in or near an avocado grove, they should be sprayed
or removed. Certain entomogenous fungi afford a partial control
of whitefly, but they cannot be relied upon for control.
During warm, dry weather this "insect" (Paratetranychus
yothersi McG.) is often found in great numbers on avocado trees.
The mite is very small, but its bright red color makes it easily
visible to the naked eye when it moves. It sucks the juices of

Avocado Production in Florida 91

mature leaves, feeding on the upper surface only and causing
the foliage to assume a characteristic rusty-brown appearance.
This discoloration is first evident along each side of the midrib
and larger veins of the leaves, but it widens as the mites extend
their feeding area until it finally covers the whole leaf. By this
time the leaves are badly devitalized and they are soon shed.
The grower should be on the lookout for the first signs of injury
during dry weather, and should not wait for browned leaves to
Control.-During the summer usually no artificial control
measures are necessary, as frequent heavy rains keep the red
spider in check. During the dry periods of winter and spring,
and during a prolonged period without rains in summer, it is
necessary to resort to dusting or spraying if the pests become
numerous. Thorough spraying with either oil emulsion or lime-
sulphur, or dusting with sulphur will effect control. Lime-
sulphur 1:60 may be used safely in winter on bearing trees.
While fruit is still on the tree it is better to dust or to spray
with oil, as the lime-sulphur is hard to remove from the fruit,
but oil gives only temporary checking. A second spraying or
dusting should follow the first in about three weeks to effect
complete control, and, rarely, a third is needed. Where only a
few trees are involved and these are fairly low-headed, a hand
duster may be used effectively. Camphor trees are a favorite
host, and where they are present they offer a steady source of
these mites for attacking avocados.
This insect (Acysta perseae Heid.) occasionally may be found
infesting the under sides of leaves in winter, but more often in
the warmer, dry spring months. It prefers the West Indian
race, although no variety is known to be free from attack by
it. The lace-bug is a sucking insect, and pale spots appear on
the foliage wherever it feeds, due to the extraction of plant
juices. The insect may be recognized by the lace-like structure
of its wings and body.
Control.-Spraying with one part of nicotine sulphate (40%)
in 900 parts of water gives good control. A spreader should be
added to the spray to make coverage more complete.
During the summer months the avocado tree may be infested
with the larvae of a small gray moth (Gracilaria perseae Busck).

92 Florida Agricultural Experiment Station

These larvae roll the leaves by drawing them inward from the
margin. They are chewing insects and give the foliage a very
ragged appearance when they are abundant. The actual damage
caused by them, however, is usually not sufficient to warrant
the expense of spraying. Arsenate of lead at the rate of 1 pound
in 50 gallons of water gives satisfactory control. If bordeaux
spray is to be applied at the time the leaf-roller is active, the
lead arsenate may be added to the bordeaux mixture, with con-
sequent reduction in the cost of application.
This beetle (Anomala undulata Mels.) occasionally appears in
great numbers at the time of blooming and devastates the bloom
spikes of avocado trees. It is a relative of the June-bug and
looks somewhat like a miniature edition of that insect in brown
and black. The insects feed at night and drop to the ground,
in the morning, to spend the day under the top layer of the soil.
They play dead when uncovered. Spraying with lead arsenate
has not seemed to have any detrimental effect on them, perhaps
because the bloom spikes are opening fresh buds constantly. A
lighted lamp held against a piece of galvanized iron with a pan
of kerosene below to catch the insects after they strike the shield
and fall has helped reduce infestations. The epidemic is transi-
tory and usually only a comparatively small number of trees is
This little insect (Frankliniella cephalica Craw.) is pale yellow
in color and about 1/25 inch long. By depositing eggs in great
numbers in the flower bases they cause the flowers to be shed
and even more damage is done by feeding on stamens and other
flower parts. On the other hand, these thrips also force their
way into many flowers which have closed after their first open-
ing, and they may pollinate many flowers in their search for
food. Whether the damage done by feeding on flower parts is
greater than the benefit conferred by accomplishing pollinations
is a question that needs and deserves careful investigation. It
may well prove that their assiduous visitations more than com-
pensate for their destructiveness.
This thrips (Heliothrips haemorrhoidalis Bouche) attacks the
upper surface of the leaves of the avocado in a way very much
like the attack of the red spider, but usually causes less severe

Avocado Production in Florida 93

injury. The work of the two may be distinguished by the numer-
out minute drops of blackish fluid left by the thrips, in addition
to the difference in their appearance. The thrips is dark brown
and has wings, while the bright red spider mite has no wings.
The Red-banded Thrips (Heliothrips rubrocinctus Giard.) is
also sometimes found attacking the avocado leaves. Where
control measures are necessary, they are the same as for the
leaf-infesting thrips.
Control.-Control of the leaf-infesting thrips is accomplished
by spraying or dusting with nicotine sulphate. If red spiders
also are prevalent it is best to spray in winter with lime-sulphur
(1:60) containing 1 part of 40% nicotine sulphate in 900 parts
of spray, or in the fall while fruit hangs on, with oil emulsion
containing the same nicotine sulphate amount. As with red
spider, it is important to recognize the presence of this pest
before the damage has proceeded so far as to seriously injure
the leaves.
This pest is the larva of an insect, and not a true worm,
although it is commonly so called. Like the leaf-roller, it is a
chewing insect, and sometimes it becomes so numerous as to
require control measures. The larvae spin a web about a cluster
of leaves during the winter and early spring months and feed
on the leaves until the pupal stage is reached.
Control-Larvae have been found which were parasitized by
small white grubs, and in some cases almost complete control has
been effected by them. If spraying is necessary, lead arsenate
may be used as for the leaf-roller.
Newly planted groves should be carefully watched for infesta-
tion with borers or sawyers. These insects are sometimes found
infesting the pith or sapwood, having gained entrance through
stubs or other exposed surfaces of the trunk or branches. They
work their way downward, destroying all growth as they go, and
may eventually kill the tree. Even large trees are sometimes
severely attacked.
Control.Preventive measures consist in removing all dead
wood present and painting the cut surfaces with pruning paint
as previously recommended under "Pruning". If infestation
is found in trees, all infested branches should be removed and
burned, and the cut ends of the branches treated as above.

94 Florida Agricultural Experiment Station

The following insects at times have become troublesome on
avocados, but are not likely to damage groves sufficiently to
warrant control measures.
Florida Red Scale (Chrysomphalus aonidium L.) is a common
pest of citrus trees in this state. It has been reported once as
-infesting heavily an avocado tree of the Mexican race, and sev-
eral times has been found in very mild infestations. If the insect
adapts itself to the avocado, control may be very difficult because
of its resistance to oil sprays of low concentration such as the
avocado can tolerate. It is necessary to spray several times at
short intervals, since only the young scale can be killed by oil
Mealybug (Pseudococcus sp.) is sometimes found on avocado
foliage, especially under shaded conditions, but the injury
caused is usually very slight. When infestations are trouble-
some in the slathouse, the insects may be washed off with a stiff
spray from a hose, or scrubbed from the leaves with a suds of
laundry or fish oil soap.
Brown Aphid (Toxoptera aurantiae Fonsc.) occasionally at-
tacks nursery trees, but the avocado is very little injured by
attacks of aphids, and even in the nursery it is not likely to
suffer seriously.
Cottony Scale (Pulvinaria psidii Mask.) has been found a few
times infesting the avocado, but no serious effects have ever
been known to result, such as would warrant spraying.
Sometimes much of the fruit on the lower branches of the
tree, and sometimes even fruit higher up, is destroyed by rats
or field mice. If the cover crop is high in the grove. while the
fruit is maturing, it should be mowed if trouble from this source
is expected, since it affords a good hiding place for these rodents.
Poisoned bait may be used if necessary. Sweet potatoes cut into
small pieces and dusted with strychnine sulphate at the rate of
1 oz. per peck give excellent results. Common soda and a pinch
of table salt are first dusted over the cut pieces, and then the
poison is added.

Avocado Production in Florida 95


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