Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 221
Title: The tung-oil tree
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Permanent Link: http://ufdc.ufl.edu/UF00026414/00001
 Material Information
Title: The tung-oil tree
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 63 p. : ill., map ; 23 cm.
Language: English
Creator: Newell, Wilmon, 1878-1943
Mowry, Harold
Barnette, R. M
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1930
 Subjects
Subject: Tung tree -- Florida   ( lcsh )
Tung oil   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references.
Statement of Responsibility: Wilmon Newell, Harold Mowry, R.M. Barnette.
General Note: Cover title.
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Bibliographic ID: UF00026414
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000923530
oclc - 18175898
notis - AEN4081

Full Text





HISTORIC NOTE


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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida







October, 1930


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
Wilmon Newell, Director





THE TUNG-OIL TREE
WILMON NEWELL
HAROLD MOWRY
R. M. BARNETTE


FIG. 1.-Tung-oil planting at the Florida Experiment Station, photographed
in the fourth year after planting.


Bulletins will be sent free upon application to the
Agricultural Experiment Station
GAINESVILLE, FLORIDA


Bulletin 221









BOARD OF CONTROL
P.. YONGE, Chairman, Pensacola RAYMER F. MAGUIRE, Orlando
A. H. BLENDING, Leesburg FRANK J. WIDEMAN, West Palm Beach
W. B. DAVIS, Perry J. T. DIAMOND, Secretary, Tallahassee
STATION EXECUTIVE STAFF
JOHN J. TIGERT, M.A., LL.D., President IDA KEELING CRESAP, Librarian
WILMON NEWELL, D. Sc., Director RUBY NEWHALL, Secretary
S. T. FLEMING, A.B., Asst. Director K. H. GRAHAM, Business Manager
J. FRANCIS COOPER, M.S.A., Editor RACHEL McQUARRIE, Accountant
R. M. FULGHUM, B.S.A., Asst. Editor

MAIN STATION-DEPARTMENTS AND INVESTIGATORS


AGRONOMY
W. E. STOKES, M.S., Agronomist
W. A. LEUKEL, Ph.D., Associate
G. E. RITCHEY, M.S.A., Assistant*
FRED H. HULL, M.S., Assistant
J: D. WARNER, M.S., Assistant
JOHN P. CAMP, M.S.A., Assistant
ANIMAL HUSBANDRY
A. L. SHEALY, D.V.M., Veterinarian in
Charge
E. F. THOMAS, D.V.M., Asst. Veterinarian
R. B. BECKER, Ph.D., Associate in Dairy
Husbandry
W. M. NEAL, Ph.D., Assistant in Animal
Nutrition
C. R. DAWSON, B.S.A., Assistant Dairy
Investigations
CHEMISTRY
R. W. RUPRECHT, Ph.D., Chemist
R. M. BARNETTE, Ph.D., Associate
C. E. BELL, M.S., Assistant
J. M. COLEMAN, B.S., Assistant
H. W. WINSOR, B.S.A., Assistant
H. W. JONES, B.S., Assistant
COTTON INVESTIGATIONS
W. A. CARVER, Ph.D., Assistant
E. F. GROSSMAN, M.A., Assistant
PAUL W. CALHOUN, B.S., Assistant.
RAYMOND CROWN, B.S.A., Field Assistant


ECONOMICS, AGRICULUTRAL
C. V. NOBLE, Ph.D., Agricultural Economist
BRUCE McKINLEY, A.B., B.S.A., Associate
M. A. BROOKER, M.S.A., Assistant
JOHN L. WANN, B.S.A., Assistant
ECONOMICS, HOME
OUIDA DAVIS ABBOTT, Ph.D., Head
L. W. GADDUM, Ph.D., Biochemist
C. F. AHMANN, Ph.D., Physiologist

ENTOMOLOGY
J. R. WATSON, A.M., Entomologist
A. N. TISSOT, M.S., Assistant
H. E. BRATLEY, M.S.A., Assistant
L. W. ZIEGLER, B.S., Assistant

HORTICULTURE
A. F. CAMP, Ph.D., Horticulturist
M. R. ENSIGN, M.S., Assistant
HAROLD MOWRY, B.S.A., Associate
A. L. STAHL, Ph.D., Assistant
G. H. BLACKMON, M.S.A., Pecan Culturist
C. B. VAN CLEEF, M.S.A., Greenhouse Fore-
man
PLANT PATHOLOGY
W. B. TISDALE, Ph.D., Plant Pathologist
G. F. WEBER, Ph.D., Associate
A. H. EDDINS, Ph.D., Assistant
K. W. LOUCKS, M.S., Assistant
ERDMAN WEST, B.S., Mycologist


BRANCH STATION AND FIELD WORKERS
L. O. GRATZ, Ph.D., Asso. Plant Pathologist in charge, Tobacco Exp. Sta. (Quincy)
R. R. KINCAID, M.S., Assistant Plant Pathologist (Quincy)
JESSE REEVES, Farm Superintendent, Tobacco Experiment Station (Quincy)
J. H. JEFFERIES, Superintendent, Citrus Experiment Station (Lake Alfred)
GEO. D. RUEHLE, Ph.D., Assistant Plant Pathologist (Lake Alfred)
W. A. KUNTZ, A.M., Assistant Plant Pathologist (Lake Alfred)
B, R. FUDGE, Ph.D., Assistant Chemist (Lake Alfred)
W. L. THOMPSON, B.S., Assistant Entomologist (Lake Alfred)
R. V. ALLISON, Ph.D., Soils Specialist in charge Everglades Experiment Station (Belle Glade)
R. W. KIDDER, B.S., Foreman, Everglades Experiment Station (Belle Glade)
R. N. LOBDELL, M.S., Assistant Entomologist (Belle Glade)
F. D. STEVENS. B.S., Sugarcane Agronomist (Belle Glade)
H. H. WEDGWORTH, M.S., Associate Plant Pathologist (Belle Glade)
B. A. BOURNE, M.S., Associate Plant Physiologist (Belle Glade)
J. R. NELLER, Ph.D., Associate Biochemist (Belle Glade)
FRED YOUNT, Office Assistant (Belle Glade)
M. R. BEDSOLE, M.S.A., Assistant Chemist (Belle Glade)
A. N. BROOKS, Ph.D., Associate Plant Pathologist (Plant City)
R. E. NOLEN, M.S.A., Field Assistant in Plant Pathology (Plant City)
A. S. RHOADS, Ph.D., Associate Plant Pathologist (Cocoa)
C. M. TUCKER, Ph.D., Associate Plant Pathologist (Hastings)
H. S. WOLFE, Ph.D., Associate Horticulturist (Homestead)
L. R. TOY, B.S.A., Assistant Horticulturist (Homestead)
STACY 0. HAWKINS, M.A., Field Assistant in Plant Pathology (Homestead)
D. G. A. KELBERT, Field Assistant in Plant Pathology (Bradenton)
FRED W. WALKER, Assistant Entomologist (Monticello)
D. A. SANDERS, D.V.M., Associate Veterinarian (West Palm Beach)
M. N. WALKER, Ph.D., Associate Plant Pathologist (Leesburg)
W. B. SHIPPY, Ph.D., Assistant Plant Pathologist (Leesburg)
C. C. GOFF, M.S., Assistant Entomologist (Leesburg)
J. W. WILSON, Ph.D., Assistant Entomologist (Pierson)
*In cooperation with U. S. Department of Agriculture.








CONTENTS


PAGE
INTRODUCTION .................................................. 5

DESCRIPTION OF THE TREE ............ ..... ...................... 8

RELATIONSHIPS AND ADAPTABILITY ................................ 11

USES OF TUNG OIL ...... ................... .. .................. 17

IMPORTS OF TUNG OIL INTO THE UNITED STATES ..... ................ 18

THE WOOD-OIL INDUSTRY IN CHINA .................................. 19

INTRODUCTION OF THE TREE INTO THE UNITED STATES ................. 23

PLANTINGS OF THE FLORIDA EXPERIMENT STATION .................... 25

OTHER EARLY FLORIDA PLANTINGS .................................. 28

ACREAGE AND DISTRIBUTION ......... .............................. 30

VARIETIES .................. ............. ........ ........... 33

ANALYSES AND WEIGHTS OF SEED. .................................. 35

CULTURE .... ........................ .. ...... ................. 36
Soils .................................................. 36
Drainage ........................................... .... 42
Propagation ....................... ......................... 42
Transplanting and Cultivation .................. ............. 46
Pruning .......................................................48
Fertilizer Tests ................. ............................ 50
Cover Crops .................... ....... .................... 53

HARVESTING ....................................................... 53

EXPRESSING THE OIL ........................ .. ..................... 54

PRODUCTS .................... .................................. 55

DISEASES AND INSECT PESTS .............. ...................... 57
Nematode ................................................... 58
Cottony Cushion Scale ....... ............................... 59
Latania Scale ................................................ 60
Diseases .................... ............................. 61

CONDENSED INFORMATION ......................................... 61

ACKNOWLEDGMENTS ........................................... 63





















FOREWORD
In 1924 Bulletin 1711 of this Station was published, giving the
then known information on the tung-oil tree and its culture in
Florida. Since then the acreage 6f tung-oil trees has appreciably
increased. considerable cultural information has become avail-
able through experimental and commercial plantings, and an out-
let for the crop has been afforded by the erection of an oil-express-
ing plant in Alachua County.
This bulletin includes information published in the above re-
port together with that which has become available through
observation and experiment during the pat six years.
!NEWELL. W ILMON. A Plelidiinary Ri.port on Expetlriieinti, with the
Tung-Oil Tree in Florida. Florida Agricultiinal Exp:-ime -nt Station Bul.
171, 1'24.









THE TUNG-OIL TREE
WILMON NEWELL
HAROLD MOWRY
R. M. BARNETTE

INTRODUCTION
The Chinese wood-oil or tung-oil tree, Aleurites fordi Hemsl.,
is one of the most interesting of the many thousands of plants
introduced from foreign countries by the Office of Foreign Plant
Introduction of the United States Department of Agriculture.
It is the source of an oil which has come into wide use in the
varnish, paint, and other industries and its culture in America
is now attracting considerable attention.
From the seeds of this tree is expressed "wood oil" or "tung
oil," one of the best "drying" oils known. When used in varnishes
this oil tends to make the varnish water-proof and reduces its
liability to crack. It is said that strictly water-proof varnish, as
well as varnish which will not turn white under long exposure to
water, cannot be made without tung oil as one of its constituents.
Its use in paints and varnishes is of comparatively recent develop-
ment and its consumption is increasing. According to David
Fairchild2, the varnishes made with this oil and southern rosin,
as two of the constituents, are superior to those made with the
high-priced and rapidly disappearing gums, such as kauri,
Manila, Zanzibar, etc.
The rather excellent showing made by bearing tung-oil trees
on the Experiment Station grounds and in later commercial plant-
ings, together with the Station's demonstration of the relative
ease with which the young trees may be grown in the nursery,
has attracted the attention of horticulturists as well as of manu-
facturers who have occasion to use tung oil in their operations.
This also has raised, quite naturally, the question as to whether
it is possible to produce tung oil profitably in this country. Condi-
tions in China make an assured and adequate supply of oil from
that country more or less uncertain. The imported oil is fre-
quently inferior in qi.ality or is adulterated. and lprlice, tlerieforl
are ibllject to, sd.!dl:en changes. An Ameriican source of supply is
much to be desired and, if such can be developed, it will doubtle-s
eCirc. 108, Bureau of Plant Industry, U. S. D. A.





















ij



.i

10


FIc. 2.-Tung-oil trees in bloom on the grounds of the University of Florida Experiment Station at Gainesville.
Planted in 1912 and 1914.







































FIG. 3.-Flower cluster of Aleurites fordi. Note that all blossoms shown in cluster are staminate ones except
the one in upper center.







Florida Agricultural Experiment Station


go far toward stabilizing and insuring the future welfare of the
paint and varnish industries, as well as furnish an income-pro-
ducing crop on a large acreage of now idle Florida lands.

DESCRIPTION OF THE TREE
The appearance of the tung-oil tree is somewhat similar to
that of the common Japanese varnish tree (Sterculia platanifolia
L.) which is commonly used in the South for street planting and


FIG. 4.-Flowers of the tung-oil tree, Aleurites fordi: pistillate (female)
flowers above; staminate (male) flowers below.







Bulletin 221, The Tung-Oil Tree


as an ornamental shade tree. The leaves of the tung-oil tree are
rather large, dark green in color, and more or less heart-shaped,
often with three lobes. Leaves of both shapes are found upon the
same tree, the lobed leaves predominating on young trees. (Figs.
14 and 15). The tree is deciduous, shedding its leaves in the fall
and remaining dormant through the winter. The clusters are
drooping and the foliage dense.
When twigs or leaf-stems are broken a milky juice exudes,
much as in the case of
Poinsettia and several
other plants belonging to
the same family.
The blossoms usually
make their appearance
slightly in advance of the
leaves. At Gainesville the
first blossoms appear at
any time from late Febru-
ary to April 10, depend-
ing upon the season. The
flowers are borne in
clusters, each blossom be-
ing white and tinged or
striped with pink in the
throat (Fig. 4). The tree
is monoecious, the flower
cluster being made up of
one or more female flow-
ers surrounded by male
flowers, there being usu-
ally only one female flow-
er to the cluster (Fig. 3).
In a count of 1,500 blos-
soms an average of 61
male blossoms was found
to each female blossom.
It is to be noted that in
the case of the flowers of
the "cluster" type trees,
as the one known as "No.
2," in the horticultural
rounds of the Florida FIG. 5.-Fruit of Aleurites fordi. Each
grounds of the Florida fruit contains from three to seven seed.







Florida Agricultural Experiment Station


Experiment Station,
there are from two to
five or more pistillate
flowers to the cluster in
numerous instances. It
is also interesting to
note that a single per-
feet flower--one having
both pistil and stamens
has been seen. The
clusters are similar to
those of the catalpa. The
tree in bloom is very
attractive.
The fruit (Figs. 5, 6,
and 7) is from two to
FIG. 6.-Fruit of Aleurites fordi. Each three inches in diameter,
section contains a seed.
dark olive green, turn-
ing to a dark or deep brown as maturity is reached. The mature
fruit is not unlike a small apple in shape. The fruits may be
separate or in clusters of two or three or more (Fig. 20). Each
fruit consists of an outer portion or husk, containing ordinarily
from three to seven firm brown seed (Fig. 8). The individual
seed in shape and color reminds one of an extremely large castor
bean, a near relative. The interior of the seed is white and the
meat decidedly oily. The seeds contain a violently purgative and
poisonous substance and must
not be eaten. When the fruit
matures it falls from the tree
and "harvesting" consists in
simply gathering the fallen
fruit whenever convenient.
The ripe fruit commences to
fall in October and all is off
the trees by about the middle
of December.
The following description
of the genus Aleurites is
given by L. H. Bailey in
"Manual of Cultivated
FIG. 7.-Cross-section of normal
Plants": fruit of Aleurites fordi.







Bulletin 221, The Tung-Oil Tree


FIG. 8.-Seed of Aleurites fordi after removal from the fruit, i. e., after
being "husked" or "hulled." These are about the natural size.

"ALEURITES, Forst.-Juice milky; leaves alternate, large, 5-7
veined from the base, entire or 3-7 lobed, the long petioles with two
glands at apex: usually monoecious; flowers in lax terminal panicled
cymes; calyx splitting into 2-3 valvate lobes at flowering time; petals
five, longer than the calyx; stamens 8-20, inserted on a conical receptacle,
in 1-4 rows, the five outer opposite the petals and alternating with five
glands of the disk; ovary 2-5 celled with one ovule in each cell, the style
divided into two thick linear branches; fruit an indehiscent drupe.
(Aleuri-tes: Greek for farinose or floury.)"

His description of Aleurites fordi follows:
"A. fordi Hemsl. China Wood Oil Tree. Tree to 25 feet high, with
glabrous branches: leaves ovate, 3-5 in. long, accuminate, truncate or
cordate at base, sometimes 3-lobed, loosely pubescent beneath and becom-
ing glabrate; flowers before the leaves, in panicled cymes, reddish-white;
petals 1 in. or more long; ovary 3-5 celled; fruit subglobose or top-
shaped, 2-3 in. diameter, glabrous, the seeds rough. (Named for C. Ford,
supt. botanic garden in Hongkong.) Cent. Asia."

RELATIONSHIPS AND ADAPTABILITY
The tung-oil tree belongs to the Spurge family Euphorbi-
aceae. There are about 4,000 species, divided among some 220
genera, in this family, some of the familiar plants being Phyl-
lanthus, Croton, Acalypha, castor bean (Palma Christa),
Euphorbias, Jatropha, and Poinsettia.
Included in the genus Aleurites are five species (Fig. 9).
These, from observations in Florida, rank in degree of hardiness
in the following order: fordi, montana, moluccana, cordata, and
trisperma. Little is yet known as to the relative hardiness of the
latter two species, so few having been planted, but it has been
demonstrated that they can survive in only the warmer sections
of the state.






Florida Agricultural Experiment Station


Qp


S


1 2 3

FIG. 9.-Fruits and seeds of Aleurites species now growing in Florida.
1. A. moluccana; 2. A. montana; 3. A. fordi. Normal fruits contain
2, 3, and 5 seeds, respectively.
Aleurites fordi Hemsl. Tung-oil tree. Wood-oil tree. Tung-
shu. Tung-yu shu. This species, a native of central and western
China, is the principal source of the tung oil or wood oil of com-
merce and is the only one now being grown in a commercial way
in Florida.
Aleurites montana, (Lour.) Wils. Mu-oil tree. Mu-yu shu. A
tree resembling fordi but apparently more upright in habit of
growth. Leaves normally 3- and 5-lobed, some cordate, with a
prominent gland nectaryy) at the base of each sinus, the glands
at the apex of petiole prominent and cupped; flowers pure white;
ovary 3-celled; fruit 11/2 to 2 inches in diameter, distinctly 3-
angled with prominent, irregular veining on surface, hull very
hard; seeds normally 3, brown, smooth. (Figs. 10, 11, and 12.)
This is the prevailing species in southern China, although both
it and A. fordi are said to be found together in some of the
Chinese provinces.
The mu-oil tree is evidently well adapted to sandy soils, this
species showing a more vigorous growth than does the fordi on
such lands at Gainesville. It, however, is considerably less hardy,
being damaged by low temperatures not affecting the latter. Cold
damage sustained, as with the tung-oil, depends mainly on the.






Bulletin 221, The Tung-Oil Tree


condition of the tree as to dormancy at the time the cold weather
occurs. The trees now growing on the horticultural test grounds,
from seed imported by the U. S. Department of Agriculture, were
severely frozen back by ordinary winter temperatures during
their first years, but in January of 1928 (in their fifth year from
seeds) they withstood 15 degrees Fahrenheit with very slight
damage. The above trees bloom profusely but have set so little
fruit that they could be of comparatively little commercial value.


FIG. 10.-Aleurites montana, the mu-oil tree, in bloom at Gainesville.


744i"'







Florida Agricultural Experiment Station


FIG. 11.-Cross-section of
Aleurites montana fruit.

cymes 4-5 inches long of


Crosses were made in 1927 by Dr.
W. A. Carver of this Station be-
tween A. montana and A. fordi, the
former species being used as the
male parent. The hybrid seedlings
are yet too young to show advan-
tages, if any, that may accrue.
Aleurites moluccana Willd3. (A.
triloba, Forst.) Lumbang. Kukui.
Candlenut. Varnish tree. Tree with
large spreading branches; leaves
large, ovate-acuminate, short-lobed,
rusty pubescent below; paniculate
many small flowers; stamens 15-20;


ovary 2-celled; fruit 2-3 inches thick; seeds large, rough and wal-
nut-like. Probably native of Malay region but now widely cul-
tivated and wild in the tropics.
Safford, in his "Useful Plants of Guam", says of it: "The
candlenut tree is widely spread over Polynesia, a' great part of
Malaysia, and the Philippine Islands. Throughout Polynesia the
nuts, strung on coconut-leaflet ribs, served the natives for candles
to light their houses. In Hawaii they are roasted, chopped up,
mixed with seaweed, and served at native feasts as a relish. They
yield an oil which is very fluid, of an amber color, without smell,
insoluble in alcohol, readily saponifiable, and quickly drying. This
oil is a mild cathartic." It is probable that this oil can be utilized
in quantity for many of the same purposes as tung oil but it is
not of the high quality of the latter. Owing to the very hard,
bony seedcoat, heavier and different machinery than that used
for tung oil extraction would be required with this species.
Comparative analyses of seeds of this species and A. fordi were
made by the Station's Chemistry Department4. The results are
given below:


A. moluccana
Percentage


A. fordi
Percentage


Meats (kernels) .............................. 31.45 60.20
Hulls (seed coat or pellicle only) ................ 68.55 39.80
Moisture in meats ........................ ..... 8.80 3.65
Oil in meats (kernels) (ether extract) ............ 58.20 57.15
Oil in whole seed pelliclee included) .............. 18.33 34.30
3Botanical description from L. H. Bailey's Cyclopedia of Horticulture.
4Annual Report, 1924, Fla. Agr. Exp. Station, p. 53R.







Bulletin 221, The Tung-Oil Tree


Fi-,. 12.- Leat ald 0tniii/natt










In Florida this species has shown itself to be more susceptible
to cold injury than either the fordi or montana. Trees are now
growing in Dade, Lee, Palm Beach, and Brevard counties but
specimen plants did not survive the cold of Alachua and Hills-
borough counties. In southern Brevard County, on Merritt's







Florida Agricultural Experiment Station


FIG. 13.-Aleurites moluccana tree growing in Brevard County.

Island, the candlenut has shown an exceptionally vigorous growth,
a tree, 7 years from seed, having a height of 25 feet and spread
of approximately 30 feet and bearing a very heavy crop of fruit
(Fig. 13).
Aleurites cordata R. Br.A. Japan Wood-oil tree. Twenty-five
to 30 feet high; leaves broadly ovate, acuminate, 3-5 lobed or
toothed; petals oblong, 34 inch long, hairy at base; stamens 8-10;
5Botanical description from L. H. Bailey's Cyclopedia of Horticulture.







Bulletin 221, The Tung-Oil Tree


ovary 3-4-celled; fruit warty; seeds about the size and shape of
castor beans. Cultivated in Japan south of 40 and in Formosa.
This species is the source of a commercial oil, known as Japan
wood oil, that differs in some important properties from the tung
oil.
A tree of this species has fruited in central Polk County, but
small seedlings were killed outright by winter temperatures pre-
vailing at Gainesville. In considering the merits of Japan wood-
oil tree as compared to those of tung-oil tree, the former, with the
little present knowledge as to its behavior under Florida condi-
tions, offers but little commercial promise.
Aleurites trisperma Blanco. (A. saponaria Blanco.) Banu-
calag. Soft Lumbang. This species, a native of the Philippines,
also a source of a desirable oil, has been reported by Edward
Simmons as having made a fair growth in Dade County.

THE USES OF TUNG OIL
In China, tung oil has been used for many centuries and is to-
day extracted from the seeds by the same crude processes that
have been in use for many hundreds of years. Among the Chinese
it has many uses, these being for the most part such uses as paints
and water-proofing materials are put to in other countries. The
Chinese junk man uses no paint on his boat or junk, but instead
coats it with the cruder grades of wood oil (tung oil). The
residue remaining after the extraction of oil from the nuts is
burned to soot and is then mixed with wood oil to form a paste
for caulking boats. Another caulking mixture is made by mix-
ing the oil with lime and bamboo shavings6.
The oil is used also as a natural varnish for houses, furniture,
and other woodwork. It is used as a water-proofing material for
masonry, cloth shoes, clothing, and paper of which Chinese
umbrellas are made,- baskets for the transportation of liquids,
etc. In fact, it is said that by its use the Chinese have been able
to get along admirably without rubber. The residue after ex-
tracting the oil is used in China as a fertilizer and in the manu-
facture of lampblack, while the burned oil and husks are used
in the making of Chinese ink, the latter familiar to all artists
and draftsmen as "India ink."
In America and other countries, tung oil is used in making
varnish, enamel paint, floor paint, flat-wall paint, paint driers,
6U. S. Department of Commerce, Commerce Report No. 33, Feb. 9, 1921.








18 Florida Agricultural Experiment Station

and, with rosin, water-proof or spar varnish. It is also used in
the manufacture of oilcloth and linoleum, for water-proofing
various sorts of cloth and other articles, and with aluminum oxide
it is made into aluminum tungate which is used as a fire-proofing
and water-proofing material. Large quantities are utilized by
the electrical industry in insulating compounds for cables,
dynamos, etc., and by automobile manufacturers in brake lin-
ings and as an undercoat in body finishing. The oil is also used
as a dressing for leather and in the manufacture of soap. Fatty
acids from it are utilized in making lacquer or substitutes for
shellac. As already stated, the oil has largely replaced the copal
gums, no longer available in sufficient quantities to meet the needs
of paint and varnish manufacturers.


IMPORTS OF TUNG OIL INTO THE UNITED STATES

From 1918 to 1929 annual imports of tung oil into the United
States almost trebled in amount, the imports for 1918 approxi-
mating 42,075,000 pounds and for 1929 almost 120,000,000
pounds. Statistics on importations for the years 1921-1929, in-
clusive, together with the value, are given in Table I.

TABLE I.-TUNG-OIL IMPORTS INTO THE UNITED STATES,
1921-1929, INCL.USIVE7.


Pounds
27,249,000
79,089,000
87,292,000
81,588,000
101,554,000
83,004,000
89,650,000
109,222,000
119,678,000


IMPORTATIONS BY


Month
January ...............
February ..............
M arch ................
A pril .................
M ay ..................
June ..................
July ...................
August ............
September ...........
October ...............
November .............
December .............


Pounds
10,276,734
7,097,159
8,811,711
S7,294,973
9,475,302
10,491,890
14,282,385
1 ), .'. ,
12,376,707
6,035,560
7,333,335


Value
$2,470,000
7,891,000
13,397,000
11,092,000
11,386,000
9,148,000
11,810,000
13,419,000
14,972,000
MONTHS, 1929.

Value
$1,309,187
876,941
1,105,030
917,222
1,181,607
1,304,289
1,784,890
1,167,088
2,115,364
1,555,166
740,395
914,905


Average price
per pound
$0.0906
0.0998
0.1535
0.1360
0.1121
0.1102
0.1317
0.1229
0.1251

Average price
per pound
$0.1273
0.1236
0.1254
0.1257
0.1247
0.1243
0.1249
0.1214
0.1275
0.1257
0.1227
0.1248


7Statistics furnished by the Bureau of Foreign and Domestic Commerce,
U. S. Department of Commerce. Valuation based on New York prices.


Year
1921
1922
1923
1924
1925
1926
1927
1928
1929


. . .




..................
. .. .. .. .. .
. .. .. .. .. .. .. .. .. .







Bulletin 221, The Tung-Oil Tree


TABLE I-A.-TUNG OIL PRICES PER POUND, PACIFIC COAST, TANK CARS8.
1928 1929
H. L. H. L.
January ........................ .151/2 .13%3 .14 .13%
February ....................... .15 .141/ .13% .12%
March .......................... .13 .12/4 .13% .12%
April ........................... .13% .12% .13% .13
May ........................... .131 .12% .13% .13%
June ........................... .13 .121/2 .13% .127/
July ............................ .141/ .12% .13% .13
August ......................... .14% ,.13% .131/2 .12%3
September ...................... .13% .13% .141/2 .12%
October ......................... .14% .13%/ .14 .131/
November ....................... .13% .13 .13% .12%
December ....................... .131 .13 .121/2 .12
Year ........................... .15% .1214 .141 .12

THE WOOD-OIL INDUSTRY IN CHINA
Although accounts of the wood oil industry in China are to be
ftud in various papers and publications, recourse has been had
mainly to the published Inventory Lists of the Office of Foreign
Plant Introduction of the United States Department of Agricul-
ture and to a bulletin entitled "China Wood Oil"9 issued by the
Department of Commerce for information as to the industry in
China. The information given under this head is taken mainly
from these publications.
The Chinese have been familiar with tung oil and have used it
for centuries. China is practically the only source of tung oil,
or "wood oil," as it is called. The latter name is not due to the
source from which it is secured but, rather, to the fact that it is
extensively used as a wood preservative, in lieu of paint or
varnish, in the Chinese provinces.
In China, nuts are secured from both wild and cultivated trees
of the two species, Aleurites fordi and A. montana, but there are
no extensive plantings under the control of individuals or com-
panies. The tree "thrives best in hilly country where the altitude
does not exceed 2,500 feet. It is also said that full-grown trees
can stand a temperature of 4 F. (this doubtless refers to A.
fordi only), but that young trees with the sap flowing may be
injured or killed by a sudden fall in temperature to 18 or 200
F."10.
It is said that the trees in China attain a height of from 10 to
30 feet and the trunks a diameter of from 6 to 10 inches, and that

8Courtesy of Oil, Paint and Drug Reporter, New York.
9Taylor, William M.: China Wood Oil. Department of Commerce, Miscel-
laneous Series, No. 125.
o10p. cit.







Florida Agricultural Experiment Station


FIG. 14.-Leaf of Aleurites fordi. Compare with figure 15. Both leaf forms
are of common occurrence on the same tree.

they commence to bear when from 3 to 6 years old, yielding from
30 to 40 pounds of seed to the tree annually.
As trees on the Experiment Station grounds at Gainesville have
nearly reached a maximum height just given and have in some
instances attained a trunk diameter greater than that given
above, it would appear that conditions in the vicinity of Gaines-
ville are at least as favorable to the tree as are those in its native
home. This is further borne out by the fact that in 1929 one of
the Gainesville trees produced a crop of 141 pounds of hulled






Bulletin 221, The Tung-Oil Tree


FIG. 15.-Leaf of Aleurites fordi. Compare with figure 14.

seed and the average production of 10 trees was over 45 pounds.
In China the harvesting, shelling, and grinding of the nuts, as
well as the extraction of the oil therefrom and its subsequent
handling, are all crude operations. The fruit is left on the ground
until the husk decays sufficiently to permit its being broken up
with comparative ease and the seed removed; in other cases, the
nuts are placed in piles and covered with straw where they are
allowed to ferment. The seed are then removed by hand. The
husked nuts are carried to small Chinese mills by means of
baskets slung on poles.
After the nuts are cleaned of trash they are roasted, then
ground by means of crude stone mills operated by manpower or






Florida Agricultural Experiment Station


by a domestic animal such as an ox or buffalo. The meal thus
produced is mixed with water and steamed, then mixed with
straw and placed in a crude wooden press. This press is fashioned
from a log and pressure is exerted by means of wooden wedges.
It is said that the type of press used has not varied for centuries.
The amount of oil wasted by this crude process is large, as much
remains in the residue and what oil is secured is usually mixed
with dirt and more or less extraneous matter. After being
strained it is placed in bamboo baskets lined with many layers of
water-proofed paper and provided with covers made of the same
material.
From the small mills the oil is purchased by agents and trans-
ported, in the baskets, by coolie labor to collection stations or to
river points where transportation to the coast begins. It is from
the collecting agents that representatives of American and other
exporting companies make their purchases.
By means of settling, much of the impure matter is eliminated
from the oil and the oil itself separated more or less crudely into
different grades, the best grade being the lightest in color.
It is said that about 90 percent of the wood oil produced in
China finds its way to Hankow as the principal distributing point.
From the western provinces, which are among the most impor-
tant oil-producing areas, the oil is transported on the Yangtze
River and in the long journey the junks carrying it are subject
to many vicissitudes. Many boats are wrecked in the Yangtze
gorges, river pirates and bandits are ever to be reckoned with
and various tolls and taxes are imposed by the military and other
officials through whose districts the boats must pass. Only to a
limited extent are steamers used for transportation of oil on the
river.
On arrival of the oil-laden junks at Hankow or other distribut-
ing points, the baskets are unloaded by coolie labor and the oil
is placed in tanks. Here further settling takes place and the oil
is separated into different grades, according to color and ap-
parent purity. Transportation of the oil from Chinese ports was
formerly in barrels, for the most part American oak barrels, but
in recent years considerable quantities have been shipped in tank
steamers.
When prices for wood oil are high the temptation to adulterate
it, while still in the hands of Chinese producers or dealers, is too
great to be resisted. This is true despite the fact that oil found







Bulletin 221, The Tung-Oil Tree


adulterated is rejected by the representatives of exporting com-
panies. Tea oil, sesame oil, tallow, and even peanut oil are said
to be among the adulterants used.
Prejudice against modern innovations, a strict adherence to
ancient customs, opposition to foreign progress, ignorance, and
the unsettled conditions in China all operate effectively against
the use of modern or labor-saving methods in the growth of the
tung-oil trees, the processes of milling, efficient methods of trans-
portation, and direct methods of selling, all of which are consid-
ered as vital necessities in connection with the supply of raw
material for any great industry.
It is little wonder, therefore, that American users of tung oil
should turn toward Florida as the place where it may be possible
to develop a permanent and dependable supply of the oil which
has become indispensable in the manufacture of many of the
products now essential to the industries and comforts of all civil-
ized peoples.
A Chinese view on the tung-oil situation is well expressed in
the following paragraphs, taken from the North China Standard,
published at Peking, November 14, 192311:
"Unless political and commercial stability soon returns to Szechwan,
American varnish manufacturers may be compelled to seek another
source for their raw products and may even have to change their
processes in order to use other products.
"When research showed that the wood oil of China could replace the
gums that were used for most of the varnish products, manufacturing
processes were adapted to the Chinese product. While prices remained
steady the oil business was profitable both to the manufacturers and
producers.
"Disturbed conditions in the province, however, have caused excessive
taxation. As Szechwan has practically a monopoly on the production,
prices have been advanced to the point where the manufacturers cannot
meet them without materially increasing the prices of the finished
products.
"Recently because the fighting has hampered the transportation the
shipments that reached the river ports were mostly adulterated."

INTRODUCTION OF THE TREE INTO THE UNITED STATES

It seems that the first seed to produce trees in America were
imported from China in 1905. In that year the United States
Department of Agriculture received nuts from Consul-General

lQuoted from Chemical Trade Bulletin 8d, Department of Commerce,
January 11, 1924.







Florida Agricultural Experiment Station


L. S. Wilcox at Hankow, China. These were received at the De-
partment's Plant Introduction Garden at Chico, California,
March 18, 1905, and presumably were planted at once. This was
about the time that American manufacturers were becoming
interested in the use of tung oil and many inquiries regarding its
source, production, etc., were evidently being addressed to Amer-
ican consular representatives in China. This interest, no doubt,
was responsible for the sending of planting stock to America for
trial by the Department of Agriculture.
In Bulletin 97 of the Bureau of Plant Industry, published in
1907, the following notes on the tree appear:

"The fruit of this tree is the source of 'wood-oil' which is being im-
ported in large quantities by this country, where it is used in the
manufacture of paints, fine varnishes, and soaps. The tree itself is of
stately appearance, with green, smooth bark and spreading branches,
making it one of the finest of shade trees. It has been styled, and
worthily so, 'the national tree of China.' The Tung-shu flourishes
throughout the Yangtze Valley in latitude 250 to 34N. It is said not
to bear when subjected to temperatures as low as 200 F., although it will
stand any degree of heat. The trees are raised from seed in a bed and
transplanted when about a foot high, and seem to do well in almost any
kind of soil. The Tung-shu is also propagated by cuttings. It is a rapid
grower and will come into bearing in from three to six years, much de-
pending upon the fertility of the soil. The yield of nuts from an average
tree.may be put at anywhere from 20 to 50 pounds, while 40 percent of
oil is obtained from the nut. The Chinese find a great many other uses
for the oil of this tree; also for its wood and the refuse from the wood
oil nut after extraction of the oil. Persons growing the wood oil tree
should be cautioned against allowing the oil to come in contact with the
skin, as it is extremely poisonous. (Wilcox.)"

From time to time in succeeding years, the Department of Agri-
culture received seed of the tung-oil tree from China, records of
which appear in the published Inventory Lists of the Office of
Foreign Plant Introduction.
Between 1905 and 1912, the Department distributed tung-oil
trees to various coopeiators in the Carolinas, Georgia, Florida,
Mississippi, Louisiana, and California, and in 1913, David.Fair-
child published a circular12 describing the tree, its uses and its
behavior at several of the southern points where it had been
planted. In this publication Dr. Fairchild expressed the opinion
that its culture would prove reasonably profitable, especially in
southern localities which do not experience too low a winter tem-
perature and where grown upon cheap land.
120p. Cit. Page 3.







Bulletin 221, The Tung-Oil Tree


PLANTINGS OF THE FLORIDA EXPERIMENT STATION

The first plantings of tung-oil trees on the grounds of the Flor-
ida Experiment Station were made in 1912. Owing to the fact
that between 1912 and 1921, the horticultural grounds at the
Station changed hands frequently, and due to the cramped
finances of the Station, full and complete notes on these trees
were not kept. Certain definite records have been located of
plantings in this row in 1912 and 1914, the assumption being that
some trees in the original planting died and were replaced two
years later.
The first record of yield of any of the 10 trees now growing is
given under date of November, 1916, and refers to two trees as
follows:
Tree No. Date Planted Yield, 1916
6 April 10, 1912 16 nuts13
7 April 10, 1912 5 nuts"S
The next record is that of November, 1918, and is as follows:
Tree No. Date Planted Yield, 1918
2 March 4, 1914 40 lbs. (4,000 nuts)14
6, 8, and 9 April 10, 1912, and
March 4, 1914 551/ lbs. (5,550 nuts)14
The 1919 and 1921 records seem to be missing, but in 1920 the
following record was made:
Tree No. Date Planted Yield, 1920
2 March 4, 1914 70 pounds
6, 8, and 9 April 10, 1912, and
March 4, 1914 75 pounds

Accurate record of yields has been kept beginning with the
crop of 1922. The yields from 1922-1929, inclusive, are shown
in Table II.
From the foregoing tabulation a wide variation in tree yields
will be noted. Some of the trees have proven to be consistently
shy bearers while the others have regularly produced fair crops.
Despite the low yields of some of the trees noted in the table and
the loss of nearly the whole crop of 1926 through injury to the
blossoms the eight-year annual average for each was 22 pounds
5 ounces of the hulled seeds these seeds containing approximately
one-third their weight in oil. It would seem that asexual
methods of propagation or, at least, careful seed selection in

13Apparently whole fruits.
14Hulled nuts or seed.










TABLE II.-YIELDS OF TEN TUNG-OIL TREES, 9TH TO 16TH YEARS, INCLUSIVE, ON HORTICULTURAL TEST GROUNDS.


1922
Tree lbs. oz.
1 17 8
2** 3 0
3 3 0
4 6 0


t-- -
5 12 8
6*** 13 8
7 8 _8
8 14 0
9 *5 8
10 8*5 8
Average 8 I 14


1923
Ibs. oz.
1 10
63 8
1 3
2 8
5 12
38 8
10 8
40 2
18 0
3 7
18 8


1924 1925 1926t
lbs. oz. lbs. oz. lbs. oz.
7 8 13 8 2 8
45 12 33 4 1 0
8 6 1 8 0 8

------ -- ---|---
7 4 3 4 0 14
3 4 3 6 0 5
39 8 52 0 0 6
11 12 19 8 0 7
37 4 16 0 12 7
89 0 75 0 10 2
23 8 0 12 6 5
27 5 21 14 3 7


fLow yield of 1926 due to 270 F. on March 13, which froze flower buds.
*Yields of the two trees taken together and evenly divided for 1922.
All weights of air-dried hulled seeds.
**Fruit borne in clusters.
***Some fruit borne in clusters some years.


1927 1928
lbs. oz. lbs. oz.
17 8 14 5
55 0 25 8
13 0 2 7
20 0 22 11
5 0 4 8
50 0 11 5
15 0 51 4
48 0 23 5
--------]I---
90 0 84 12
14 0 9 2
32 12 20 5


1929 8-yr. tot.
lbs. oz. lbs. oz.
37 6 111 13
89 12 316 12
4 14 34 14
31 0 93 9
4 6 39 1
66 14 272 1
S35 12 106 11
39 5 230 7
141 11 514 1
5 0 67T 2
S45 9 223 5
i-- --V -I 2


8-yr. avg.
lbs. oz. o
13 15 .
39 9
4 6 .
11 11
4 14
34 0 0
13 5
28 13

64 4
822 6
22 5 *


'I
.I


!


I


t







Bulletin 221, The Tung-Oil Tree


planting would tend to make for trees of a more uniformly heavy
bearing habit.
These trees (Fig. 2), spaced 10 feet apart in the row, grow
upon a gentle south slope on very sandy soil. They have received
very little cultivation and, so far as is known, no fertilizers prior
to 1923. Beginning with the spring of 1923 these trees were
given annually 10 pounds each of a commercial fertilizer analyz-
ing approximately 6% ammonia, 8% phosphoric acid, and 4%
potash. This fertilizer was composed of dried blood, sulphate
of ammonia, nitrate of soda, ground steamed bone, super-
phosphate, and sulphate of potash. They now average over 25
feet in height and 331/ feet in average spread of branches. Their
trunk diameter, at a distance approximately 12 inches above the
ground, varies from 7 inches to 22 inches, the average diameter
being slightly under 12 inches. The largest tree has a height of
28 feet, a spread of 391/2 feet, and a trunk diameter of 22 inches.
The accompanying table, containing data taken from the
United States Weather Bureau records of the Gainesville Station,
shows the minimum temperatures to which the older bearing
trees on the Station grounds have been subjected.
TABLE III.--SHOWING THE NUMBER OF DAYS WITH MINIMUM TEMPERA-
TURES OF 320, 250, 20, AND 160 OR BELOW, RESPECTIVELY, AT
GAINESVILLE, BETWEEN 1912 AND 1929.
Winter of 320 25 200 16
1911-12 ....................... .. 17 2 0 0
1912-13 ........................ 3 0 0 0
1913-14 ........................ 10 0 0 0
1914-15 ........................ 8 1 0 0
1915-16 ........................ 18 1 0 0
1916-17 ........................ 14 3 2 0
1917-18 ........................ 21 11 2 0
1918-19 ........................ 9 3 0 0
1919-20 ........................ 18 1 0 0
1920-21 ........................ 1 0 0 0
1921-22 ........................ 5 0 0 0
1922-23 ...................... 6 1 0 0
1923-24 ........................ 12 2 0 0
1924-25 ........................ 4 0 0 0
1925-26 ........................ 11 4 0 0
1926-27 ........................ 11 3 1 0
1927-28 ........................ 8 7 1 1
1928-29 ............ ............ 13 4 0 0
The absolute minimum experienced by these trees was 150 F. on
January 3, 1928.
Comparative temperature data for various locations in Florida
are available in Bulletin 20015 of this Station.

15Mitchell, A. J., and M. R. Ensign. The Climate of Florida. Florida Agr.
Exp. Station Bul. 200. 1928.







Florida Agricultural E.,p( rri, nt Station


Further plantings were made in 1922 and 1923 to ascertain the
effects of various fertilizer materials on growth and yield.
Results thus far obtained are reviewed under the paragraph on
fertilizer tests.
In the spring of 1930 plantings comprising some 11 acres were
made at the Station at Gainesville and in a cooperative planting
in Columbia County for the purpose of furnishing reliable and
definite data as to the relative merits of the "single" and "cluster"
types and of budded and seedling trees.

OTHER EARLY FLORIDA PLANTINGS

To the enthusiasm and experimental work of the late William
H. Raynes, a well-known horticulturist of Tallahassee, is due
much of the credit for what developments have already taken
place in connection with the tung-oil tree in Florida. Mr. Raynes
was undoubtedly the first to atteimpt-the growth of- the tree in
the South. '6n November 15, 1906, he planted five one-year-old
trees which had been sent by the Department of Agriculture to
the superintendent of the cemetery at Tallahassee, and which, in
turn, had been given to him. Mr. Raynes kept careful notes, which
have been available through the kindness of B. F. Williamson,
of Gainesville.
In spite of the careful nursing of the five trees, all but one died.
On March 24, 1907, a severe gale nearly destroyed this one and
it had to be cut back to a height of three feet.
In 1908 the tree blossomed and that year produced three fruits
-just "three years from the planting of the seed nut at Chico,
Cal." This tree evidently came from the first importation of
seeds in 1905.
In 1909 the tree produced 64 fruits, and in November of that
year the owner planted them and grew trees which he later dis-
tributed to other persons.
The tree produced 88 fruits in 1910 and 344 in 1911. At this
point Mr. Raynes sent to the Department at Washington 286
fruits, or a bushel of unshelled seed, this being the first bushel of
tung-oil nuts produced in America.
A severe freeze occurred November 25, 1911, but the original
tree "pulled through the winter all right" and came out with a
heavy bloom in April. Mr. Raynes' notes also show that, from
nuts planted November 1, 1911, the first seedlings were just ap-







Bulletin 221, The Tung-Oil Tree


pearing on April 17, 1912. That year his tree produced 852 whole
fruits and these he sent to. Washington. He also records that in
November of that year his tree had a circumference of 24 inches
at a point 12 inches from the ground and that the spread of the
branches was 23 feet. He also supplied a number of yearling
trees to Tenant Ronalds, at Tallahassee, whose plantings will be
mentioned later.
In 1913 Mr. Raynes' original tree produced 1,095 fruits, out of
which he got a bushel of shelled seeds. These he sent to L. P.
Nemzek, representing the Educational Bureau, Paint Manufac-
turers' Association of the United States, Gillsboro, New Jersey.
From these seeds Mr. Nemzek produced 2.2 gallons of oil-the
first American-grown tung oil.
On February 26 and again on March 22, 1914, freezing
temperatures were experienced at Tallahassee. The latter freeze
came when the blossoms were just putting out and as a conse-
quence the production in 1914 was low. Mr. Raynes' records show
that on July 1 of the same year he put in two buds on growth of
the current year, that they took steadily and grew nicely.
Mr. Raynes kept notes to some extent on the blossoming dates
and on the time of dropping of the first and last fruits of each
season's crop. The data shown in the following table are interest-
ing as showing the reaction of the tree to seasonal conditions at
Tallahassee.

Blossoms First Ripe Last Ripe
Year Appeared Fruit Fell Fruit Fell
1909 ................ ? September 4 October 11
1910 ............... ? September 18 October 24
1911 ................ ? September 3 November 25
1912 ................ April 3 September 10 October 19
1914 ................ March 29 September 14 October 15

By consulting the records of the Weather Bureau, the minimum
temperatures to which the Raynes tree has been subjected at
Tallahassee are readily determined. Table IV shows the number
of times, between 1904 and 1924, that minimum temperatures of
320, 250, 20, and 16' or below, respectively, have occurred. For
example, during the winter of 1923-24 a temperature of 16 was
observed once and a temperature of 200 or below was observed
twice, the latter including, of course, the occasion upon which
the temperature went as low as 16.







30 Florida Agricultural Experiment Station

TABLE IV.-NUMBER OF DAYS WITH MINIMUM TEMPERATURE OF 320, 25,
200, AND 160 OR BELOW, RESPECTIVELY, AT TALLAHASSEE,
BETWEEN 1904 AND 1924.
Winter of 32 250 200 160
1904-05 ........................ 17 2 2 0
1905-06 ........................ 10 0 0 0
1906-07 ........................ 8 2 0 0
1907-08 :....................... 10 1 0 0
1908-09 ........................ 3 2 0 0
1909-10 ........................ 21 2 2 0
1910-11 ........................ 15 3 0 0
1911-12 ........................ 18 4 0 0
1912-13 ........................ 2 0 0 0
1913-14 ........................ 11 0 0 0
1914-15 ........................ 12 1 0 0
1915-16 (incomplete) .......... 10 0 0 0
1916-17 ........................ 15 5 2 1
1917-18 ........................ 25 10 4 0
1918-19 ........................ 10 3 2 0
1919-20 ........................ 18 2 0 0
1920-21 ........................ 2 0 0 0
1921-22 ......................... 8 0 0 0
1922-23 ........................ 4 1 0 0
1923-24 ........................ 12 4 2 1
Mr. Raynes died November 12, 1914. Shortly afterward his
home was burned and the tung-oil tree, being nearby, was
severely injured. The tree in 1924 was 27 feet high and the trunk
had a circumference of 52 inches at a distance of one foot from
the ground (Fig. 16). In 1923 it produced about 150 pounds of
whole fruits.
In 1913 Tenant Ronalds, of Tallahassee, became interested in
the tung-oil tree and planted four acres. This was to become the
first bearing tung-oil grove in Florida. In 1915 he increased his
plantings to 40 acres (Fig. 17). The grove was well cared for
until the freeze of 1917, when young nursery stock and young
grove trees were killed. For several years thereafter no care
was given the planting except that it was pastured and occasion-
ally mowed. Beginning about 1925 a portion of the trees were
fertilized but given no cultivation. This has resulted in a partial
rejuvenation of those trees and an increase in yield.

ACREAGE AND DISTRIBUTION

No exact data are available as to the acreage of plantings in
the state, although carefully checked estimates place the acreage
at approximately 5,000. This acreage is mainly in north central
and northern Florida, with the major portion in Alachua, Clay,
and Levy counties. Numerous smaller plantings have been made
in other counties, but of these very few are in the southern areas.







Bulletin 221, The Tung-Oil Tree


FIG. 16.-Oldest tung-oil tree in Florida, planted November 15, 1906,
by William H. Raynes near Tallahassee.

Until such time as plantings have been made and followed with
proper cultural methods for a period long enough to show con-
clusive results, any statement as to the reaction of the tree in
untried soil types and under varied untried climatic conditions is
largely a matter of conjecture. The reaction of the tree itself
is the only reliable criterion as to its adaptability to specific loca-
tions and soils when plantings are not known to exist under
similar conditions.






Florida Agricultural Experiment Station


FIG. 17.-Bearing grove of tung-oil trees on property of Dr. Tenant
Ronalds, Tallahassee.
Just where the northern and southern limits for the success-
ful culture of the tree may be is as yet not known. Minimum
winter temperatures will determine the northern boundary. Both
mature trees and nursery stock have withstood a temperature of
15 degrees Fahrenheit at Gainesville without apparent damage.
Any damage from freezing will depend mainly on the condition
of the tree at the time the cold weather occurs. If in only a
partially dormant condition, as might happen in early fall or
spring, damage might result from low temperatures that would
have no ill effect on completely dormant stock. There is no means
of knowing the southern limits for satisfactory growth until
these are determined by a sufficient number of plantings made
under varying conditions in southern Florida.
From over 300 lots of trees or seeds sent from this Station
for testing purposes in the past six years, quite varied results
have been reported. With these test lots it appears that in







Bulletin 221, The Tung-Oil Tree


Nr-
-4,


Fih 1-. -- (',i.i.tic- re .,rting a
ti, ..ial.le i ..' th 't' t Iung-"il


rmany cz;e,, thle t'ret \ were n', 't giv _ei
tiLe attention tlhe would 1a i:- re-
c>-iv,:d -haid they Ieen gri'nw n in a c mInlrciial \way. hut rather \\were- planted
Silld allowed to shift fori them-iel\e',.
As wouLld be expected. contrary re-
ports asl to re'lllts \werle received from
the -.l iite counties. some from tlhe
- ... .,. :..: + ...... I. 1 ., I .-.; ,I -1.,.. f.-,


0 1~



NK





-' .-7--1


, imIeI'- \r I LI -l:"-. lp'1 -iiiaiil'v I ) 'ii l t I -- i
dilfference,- in .soils and cultural attentions gil en. -9, --t
It i' t:o l- noted that ~llome few' relprt, from the
niorthlwe-tern c.intie-s indicated -ome cold '
damage to the trees or late frost damage to the
blossoms. Any cold damage apparently was chiefly to young
stock. In nearly all instances failures were reported from plant-
ings on wet, poorly-drained soils. Where one or more favorable
reports of satisfactory growth were received from a county, that
county is so marked on the accompanying map (Fig. 18). As
plantings were not made in all counties, nor reports received
from all test lots sent out, the absence, of markings designating
favorable reports would not necessarily indicate those counties
to be unsuited to the growing of tung-oil trees. Conversely,
neither should a favorable report from a given county be con-
strued as meaning that all soils and locations in that county are
adapted to tung-oil culture.


VARIETIES

As with most seedling trees there is considerable variation to
be noted in tung-oil trees grown from seeds. This variation takes
the form of varying sized fruits, trees showing an abnormal
predominance of staminate flowers or lack of pistillate blossoms
resulting in low yields, fruits differing from the normal in hav-


I






34 Florida Agricultural Experiment Station

ing a flattened oblong shape and containing as many as 18 seeds,
and a difference in the number of fruits borne at the twig
terminals. The last difference has led to the tentative designa-
tion of the so-called "single" and "cluster" types or varieties
(Fig. 19). The "single" bears but one fruit to the twig, the
"cluster" more than one, as many as 19 being seen, in the same
position.



















FIG. 19.-The difference in manner of fruit production which has led to
the tentative distinction of "cluster" (right) and "single" (left) types.
Foliage partially removed to show fruits.

Some observers contend that whether a tree is of the single
or of the cluster bearing habit is dependent solely on the thrift
of the tree and amounts of available plant nutrient materials in
the soil prior to and at the time of bud differentiation. If this
speculation be correct, any and all trees are at one and the same
time both "singles" and "clusters", their status as either being
entirely due to the condition of thrift. In contradistinction to the
above assumption the older ten trees at the Station in eight years'
close observation have shown no tendency to alternate or switch
their mode of bearing from year to year. One of these trees has
consistently borne the most of its fruit in clusters, one other a
portion of its fruit in clusters, and the remaining eight, without
observed exception, bearing all fruit singly. All have received
like amounts and kinds of fertilizers and cultivation.
All Station plot plantings over a three-year period have shown






Bulletin 221, The Tung-Oil Tree


the higher average yields from the "cluster" trees. However, the
one tree showing both the highest annual and the highest total
yield over an eight-year period has consistently borne its fruit
singly (tree No. 9, Table II).
A rather uncommon variance from the normal in size and
shape of the fruits has been noted in some trees, the fruits being
very large, round to oblong in shape, occasionally quite flattened,
and containing many small seeds. This variation has been
termed by some the "Craig" variety after the name of the owner
of the property where first noticed. Although some of the fruits
are striking in appearance, this so-called variety has not shown
any superiority over good trees bearing normal fruits.
Until such time as plantings now made have demonstrated the
practicability of using budded stock instead of seedlings it would
seem advisable to plant seed from only those trees showing the
more desirable characteristics.

ANALYSES AND WEIGHTS OF SEED
Analyses, made by the Station's Department of Chemistry, of
the pomace or press cake remaining after the oil is extracted
from the seeds, and of the outer hulls show both to have potential
fertilizing value. Of the lots analyzed the press cake contained
5.9 percent nitrogen, 1.97 percent phosphoric acid, 1.41 percent
potash, and 6 percent moisture. The hulls showed 14.4 percent
moisture, .74 percent nitrogen, .38 percent phosphoric acid, and
3.09 percent potash.
A definite reaction of plants on Florida soils to the use of the
above materials as fertilizers has not been determined because
of the small quantities yet available. This reaction, however, is
assumed to be satisfactory. The pomace, like the seeds, is
poisonous; thus, its use is limited to that of a fertilizer material.
It cannot be used in stock feeds.
Dr. H. A. Gardner, of the Scientific Section, American Paint
and Varnish Manufacturers' Association, Washington, D. C.,
reports the following analysis of Florida-grown tung-oil fruits:
Percentage of hulls ............................... 55
Percentage of meat ................................ 45
Percentage of oil in meat .................. .......... 49
Percentage of oil in seeds (seed coat intact)............32-39
Fully matured and thoroughly air-dried fruit will run, by
weight, approximately 56 percent of seed and 44 percent of hulls.
Unhulled, dried fruits from different trees have been found to
vary in number from 340 to 450 to the bushel. Of several lots






Florida Agricultural Experiment Station


the average bushel weight was 303/4 pounds, there being 17
pounds 10 ounces of seeds and 13 pounds 2 ounces of hulls. The
number of seeds in a bushel of fruits in the hull varies from 1,780
to 2,000, with an approximate average of 1,900. The number of
hulled seed in a pound varies from 100 to 164. Averages of all
fertilizer plots in 1927 showed 149 seeds to the pound from the
"cluster" trees and 132 to the pound from the "single" trees.

CULTURE
In addition to rightly grown nursery stock which has been
properly transplanted, it now seems definitely established that
maximum thrift and yields are dependent upon four basic re-
quirements, namely, suitable soils, thorough drainage, ample
cultivation, and adequate fertilization.
SOILS
Although plantings have been made on a variety of soils, it is
not yet possible to define either the most suitable soil type or out-
line the regions where tung trees may be successfully grown, this
being due to the absence of older plantings on each of the several
soil types in varying locations in the state. Soil samples have been
taken and general observations of tree growth noted in many
plantings. The soil samples have been taken mostly at varying
depths that the soil profile may be known. Such samples of the
various soil types have been tested in the laboratory for their
reaction (pH value16) and certain other characteristics.
From the results of these tests it appears that the tung-oil tree
under Florida conditions thrives best on an acid soil. This can-
not be made a hard and fast rule, as under conditions of high
organic matter content it is possible that a satisfactory growth
may be obtained with relatively large additions of lime to the soil.
Such favorable conditions for liming do exist on certain highly
organic soil types which are encountered in the area suitable
from a climatic standpoint for the culture of the tree.
As is characteristic for tree crops, the well-drained types are
the most extensively planted soils. The Norfolk is perhaps the
16The pH value of a soil suspension is a measure of the degree of acidity
or alkalinity of the soil. The scale is such that the number 7 represents a
neutral condition; that is to say, a condition under which there is not an
excess of acidity or alkalinity. Numbers greater than 7 represent an
alkaline condition, the degree depending upon the number, the larger the
number the greater the degree of alkalinity. In the same manner, numbers
smaller than 7 represent an acid or sour condition, the degree of acidity de-
pending on the smallness of the number.






Bulletin 221, The Tung-Oil Tree


most extensively planted soil series. Sands to sandy loams are
planted to tung-oil, the finer sands and loams as a general rule
making excellent soils for its growth. A system of cover-crop-
ping with summer legumes, possibly followed by a winter legume,
will no doubt prove of value for these types, as will also a system
of mulching.
Other well-drained soils which have been planted to tung-oil
trees include the Gainesville, Orangeburg, and Greenville series.
The Gainesville differs from the Norfolk in having particles of
phosphate and limestone in the soil and is of a brown to a reddish-
brown color. The Orangeburg has a surface soil of gray to almost
black with a red to yellow subsoil. A red to brownish-red surface
soil and a red subsoil characterize the Greenville series.
Plantings have been made also on flatwoods soils in the
Blanton, Bladen, Portsmouth, and Leon series. These acid soils,
usually high in organic matter content, are suitable when they
are sufficiently drained. The Bladen series, with its soft, friable,
dark gray surface soil and its yellow to drab colored subsoil of
sand with clay, seems well adapted when adequately drained.
This type of soil should require less fertilizer than the Norfolk
series, or at least react more to fertilizer applications. The Ports-
mouth series, with its black to gray surface soil and its hardpan
at a deep level, and the Blanton series with a gray surface soil
and a light-yellow and white splotched sandy subsoil are also used
even if they are not as valuable as the Bladen series. Even the
Leon hardpan series has been planted when adequate drainage
is provided below the hardpan, which usually occurs at from one
to three feet below the soil surface. The roots of the tree appear
to penetrate very effectively the hardpan when the drainage is
placed below this usually impervious layer.
The question of whether or not the tung-oil tree should be
planted on the well-drained types of soil or on the "flatwoods"
type of soil may resolve itself into a question of economics. If
drainage of the latter may be effected at a cost which is not pro-
hibitive, it is possible that a significant saving on the fertilizer
costs may be effected on these types due to their greater natural
fertility. On the other hand, with an adequate system of cover-
cropping and a more or less liberal use of commercial fertilizers,
the culture of tung-oil trees on the well-drained soil types may be
more profitable when drainage costs are considered. The ques-
tion of soil type evidently will be governed partially by local condi-







Florida Agricultural Experiment Station


tions, and by the economical factor of the demand and the supply
of the product-tung oil-which will control the price of the
commodity.
Aside from the general fac-
tors of native fertility of the .

mercial fertilizers, and drain-
age, there are two soil condi-
tions which appear to develop a
definite injury to the tung-oil
tree. An excess of lime in the
soil and a soil reaction above
pH 7 are liable to cause a chlo-
rotic condition which is charac-
terized in Fig. 20 and in the
leaves as shown in Fig. 21. Be-
sides being malformed, the W
leaves are yellow to bronze in
color and the growth of the
seedlings is characterized by
short internodes and a bunched
formation of growth as shown
very well in Fig. 20. The yellow
leaves are noted on the new
growth at the top of the plant.
Figure 23 represents a stunt-
ed plant removed from an over-
limed area (pH value 8.04) in FG. 20. Chlorosis of tung-oil
foliage due to an excess of lime in
a nursery and planted in the the soil.
same soil which had not re-











FIG. 21.-Chlorotic and mal-formed conditions of leaves
due to an excess of lime in the soil.







Bulletin 221, The Tung-Oil Tree


ceived an excess of lime and
had a pH reading of about
6.35. The seedlings developed
from their poor growth on the
limed soil and made a good
growth on the more acid soil.t .
The overliming was due to the .
lime being dumped on the
limited areas some 10 to 12
years before the nursery was
established. These small areas
of soil where the lime was
dumped still show a reaction
of about 8.04, and the trees
were definitely stunted as
shown in Fig. 23. However, .
when these seedlings were -
placed in the soil which was i T
not overlimed (pH 6.35) they -
grew out of the trouble as t s
shown in Fig. 22.
However, when healthy
seedlings from outside the
overlimed area (which had a
pH of approximately 6.35)
were placed in soil from the FIG. 22.--Showing recovery of a
overlimed area the conditions stunted tung-oil plant after removal
from an over-limed soil to a soil with
shown in Fig. 20 were ob- an acid reaction.
trained. A study within the
nursery itself gave the results obtained in Table V.
Another characteristic injury to this tree, apparently due to
a soil condition, is a bronzing of the leaves with a shortening of
the internodes, a bushy growth and ultimate dying-back result-
ing. Often the tree dies back to such an extent that it sends out
shoots just above the ground, these shoots ultimately being
affected and dying-back until finally the tree succumbs. This in-
jury is noticed most extensively in a commercial planting near
Gainesville where the soil classification is doubtful17. This soil
17From descriptions it appears that this soil resembles the Hernando series.
A gray to light brown or yellowish-brown surface soil is underlain by a
reddish-brown subsoil which grades into a mottled reddish-brown clay in the
heavier types. The soil is underlain by calcareous material with some
phosphate.







Florida Agricultural Experiment Station


FIG. 23.-Stunted growth of tung-oil trees in a small area of a nursery
due to liming, with consequent alkaline reaction of soil.

TABLE V.-THE OCCURRENCE OF CHLOROSIS AND BRONZING OF ALEURITES
FORDI AS INFLUENCED BY EXCESSIVE LIME APPLICATIONS IN
NURSERY STOCK, SEPTEMBER, 1928.


Application of lime

Small amounts of lime applied
10 to 12 years before planting of
nursery.
Lime dumped on ground.
Limited area of excess lime.

Lime dumped on ground.
Limited area of distinctly exces-
sive lime.


Condition of
Seedling Tree
Good growth
of seedlings

Bronzed seed-
lings; some died
out.
Seedlings show-
ing character-
istic bronzing.


Depth of pH of
Soil Sample Soil Sample
(inches)
0-9 6.10
9-21 6.10
0-9 7.90
9-21 7.87
0-9 8.21+
9-21 7.62


has from 6 to 18 inches of a good surface soil underlain by a yel-
low to reddish-brown subsoil which grades into the original lime-
phosphate formation with a rather plastic clay mottled with red
and yellow as an intermediate product. The depth of the soil
varies according to the lime phosphate formation underlying it.
This gives a spotted appearance to the grove, the better trees be-
ing found in the pots or deeper formations of the soil. The trees
were from two to three years old when the first indications of
injury were noted, injury being detected in the shallow soils first.
To date, many trees in the above planting are affected by this







Bulletin 221, The Tung-Oil Tree


bronzing and dying-back. The only correlation with a soil condi-
tion is found in the total phosphate content of the soil and the
appearance of the disturbance as shown in Table VI.

TABLE VI.-ANALYSES OF SOILS SHOWING THE RELATIONSHIP BETWEEN
THE PHOSPHATE CONTENT OF A SOIL AND THE DEVELOPMENT OF
"BRONZING" IN THE TUNG-OIL TREE.

Condition Depth of
Condition Dept of Description of pH Total %
of tree (inches) soil layer of soil P205
Bronzed 0-6 Light brown loose friable 6.60 0.445
tree fine sand.
dying-back 6-18 Loose friable fine sand 6.60 0.905
with some fragments of
phosphatic lime rock.
18-30 Increase in clay grading 6.50 1.840
into phosphatic lime rock.
Bronzed 0-6 Loose friable fine sand 6.85 0.705
tree with fragments of phos-
dying-back phatic lime rock.
6-18 Plastic mottled clay with 6.73 1.720
Fragments of phosphatic
lime rock.
Apparently 0-6 Loose friable sand. 6.40 0.200
healthy 6-18 Loose friable sand. 6.70 0.155
tree 18-30 Clay at 30 inches. 6.63 0.440

It is noted from these data that the pH of these soils is slightly
on the acid side. In the soil from around the trees in which the
malgrowth took place there is a significantly higher content of
phosphorus pentoxide (P205). Thus a definite correlation is to
be seen between the phosphate content of the soil and the develop-
ment of the bronzed condition. The bronzing of the leaves and the
malgrowth were correlated with the depth and character of the
soil above the phosphatic lime rock underneath. As the trees
have become older there is an increase in the amount of the bronz-
ing which indicates that the cause lies in the lower depths of
the soil.
Soil was removed from the three to four foot and from the four
to five foot depths in the affected area, and placed in pots in the
greenhouse. The soils were obtained on August 7, 1928, and
tung-oil seedlings were placed in them on that date. All the seed-
lings lived and at first made a fair growth. However, as early as
September 10, 1928, spots began to appear on the leaves of all
the seedlings, and after that time the seedlings made no further
growth. Figure 24 shows the condition of the seedlings one and
one-half years after they had been planted.







Florida Agricultural Experiment Station


In a typically affected area in the grove where the trees were
not dying but where they were showing the bronzing of the
leaves, a number of trees were selected for special fertilization
and treatment. Among the chemicals tried were ferrous
sulphate, manganese sulphate, lime, sulphuric acid, acid phos-
phate, potassium sulphate, and potassium chloride, as well as a
large application of manure. The chemicals were placed on the
surface soil around one group of trees and at the roots of another
group of trees directly in the injurious subsoil. This was accom-
plished by digging holes around the tree, putting the chemicals
into the solution and pouring them into the holes. While some
of the trees were caused to shed their leaves by several of the
more drastic treatments, they again put out new growth. How-
ever, to date, results have
S- been negative as far as over-
coming the bronzed and dy-
ing-back condition of thetree
is concerned.
Further studies of these
physiological disturbances in
the tung-oil tree will be made
in an attempt to find the
cause and the treatment of
S them. However, for the time
being it seems best to stay
away from these two condi-
tions in making new plant-
ings. DRAINAGE
Without sufficient drain-
age the trees will not con-
tinue to show a thrifty and
satisfactory growth, irre-
spective of other cultural at-
tentions given them. Surface
drainage only is not suffi-
cient; the water table must
be considerably below the
soil surface level.
PROPAGATION
FIG. 24.--Showing stunted growth Present plantings are
of a tung-oil tree planted in soil con-
taining a natural excess of phosphates. composed wholly of seedling







Bulletin 221, The Tung-Oil Tree


stock. The common practice is to plant seeds in a nursery bed in
February, the seedlings being transplanted to permanent field
positions after one season's growth. One-year seedlings, under
normal weather conditions and with proper soils and culture, will
have attained a height of from 3 to 6 feet. The nursery method
seems to be preferable to planting seeds directly in the field where
the trees are wanted in that the cost of required cultivation for
the same number of trees is almost negligible in the nursery as
compared with field plantings.
The seeds do not remain viable over an extended period and,
if to be used for planting purposes, must be planted during the
season following their maturity. In the nursery row they are
planted at a depth of 2 to 4 inches, spaced 8 to 12 inches apart
in the row with the rows not closer than three feet. Approx-
imately 60 days are required for germination. Hulled seeds only
should be planted as the planting of whole fruits results in a
cluster of more or less spindling and malformed seedlings which,
because of their crowded condition, do not develop into straight,
vigorous stock.
Frequent and shallow cultivation should be given from the time
the seedlings appear until midsummer.
Complete commercial fertilizers, barnyard manures, and vary-
ing forms of nitrogenous fertilizers have all been used to advan-
tage in the growing of the young trees. One or two applications
are made, the first after the seedlings are a few inches high and
the second in early summer.
Careful seed selection will no doubt tend toward greater yields.
In such selection only carefully collected data will show constant
differences in the yields of individual trees. Reference to Table
II will show a striking contrast in annual production of the trees
in question. There are other factors than inherent prolificacy
influencing fruitfulness, but from these comparative figures it
would seem that more productive progeny could reasonably be
expected from the higher yielding parent trees. Whether seed
selection alone will perpetuate a high yielding strain has not been
definitely established, although, obviously, it should tend to lower
the percentage of shy-bearing trees. Desirable inherent chaiiic-
teristics of a given tree can be preserved tlu l.',:,-:h thle nlediiu of
vegetative propagation, the tendency in the tiuw--oil tree to
"sport" probably being no greater than in the average fruiting
tree. Of the asexual propagation methods, budding appears to







Florida Agricultural Experiment Station


be the most feasible, as growing the trees from cuttings has met
with little success.
If found to be desirable, budding may be practiced (Fig. 25).
In this operation the patch bud and the ring bud, because of the
thickness of the bark, have been found to be the most satisfactory
(Fig. 26). The work is done in early spring just as soon as the
bark slips readily. The most satisfactory budwood is wood of
the previous sea-
son's growth.
Mr. C. B. Van
Cleefis has shown
that vigorous seed-
lings, of stock from
seeds planted the
previous February,
can be budded in
August and Septem-
ber so that budded
trees may be had in
one year from the
time of seed plant-
ing. On stock of this
age, shield budding
is possible. The scion
wood used is from
the current season's
growth.
A fairly large per-
centage of the buds
are "blind," but even
a cursory examina-
tion will disclose
most of these so
"-. there need be little
loss in propagation
due to this cause if
care is used as to
selection when cut-
ting the buds. Buds
FIc. 25.-Budded tung-oil tree. Budded in
April on 2-year root; photographed the follow- 'sGreenhouse fore-
ing November, the height then being 7 feet 8 man, Florida Experi-
inches. ment Station.







Bulletin 221, The Tung-Oil Tree 45


FIG. 26.-Detail of patch budding of tung-oil tree.







Florida Agricultural Experiment Station


after insertion are firmly bound in place with waxed cloth, the
same as is commonly used in citrus budding. After a week or
ten days the bud and stock will have formed a union at which
time the cloth wrapping is removed. At the same time, the
stock is "lopped" by cutting, on the budded side, about three-
fourths through, five or six inches above the bud, and bending
over the top. This leaves but a narrow strip of bark to support
the nearly severed top and forces the bud into active growth.
After the bud has attained a height of five or six inches the stock
is neatly cut off just above the point of union of stock and bud.
Neither staking nor tying of the growing buds has been neces-
sary.
One- or two-year trees are the most satisfactory for budding.
Dormant grafting has given very unsatisfactory results. Bark
grafting on larger trees during the summer months can be prac-
ticed with a fair degree of success.
Buds of A. fordi readily form a union with stocks of A.
montana.

TRANSPLANTING AND CULTIVATION
In general, the same methods are used in transplanting tung-
oil trees from the nursery to the grove as with other fruit or
nut trees.
In this connection, the question of the distance to plant nat-
urally presents itself. As there are no mature groves of tung-
oil trees in the United States, the answer to this question is yet
largely problematical. On the strength of the size attained by
the trees in China some have recommended that they be planted
as close as 20 feet each way. However, it seems that this is too
close for Florida conditions where, with good care, the trees ap-
parently exceed in size those of China. It should be remembered
that the latter are practically uncultivated, receive little or no
fertilizer, and are said to grow upon the poorest f' soils.
It would seem best, in the light of present information, to set
the trees 25x25, 25x30, or even 30x30 feet apart. However,
in order to economize in the matter of cultivation and care it
appears entirely practical to plant the trees, say, 25 or 30 feet
one way and half this distance the other, with a view to trans-
planting alternate trees to other groves when they, become
crowded. There is every reason to believe that trees several
years of age can be transplanted successfully, if as great care be
observed, for example, as in transplanting large citrus trees.







Bulletin 221, The Tung-Oil Tree


In setting the trees it is
of utmost importance that
they are not planted too
deeply. The proper depth is
that at which they stood
in the nursery row and if
planted much deeper it may
be the cause of failure in
these trees.
All malformed nursery
stock or trees which have
become stunted from any
cause will ordinarily fail to
grow into vigorous field
trees irrespective of later
attentions given. A rigor-
ous grading and discarding
of all nursery stock below a
high standard is of utmost
importance as an initial
step toward a thrifty per-
manent planting.
It is important that the :.
trees be transplanted while
dormant -that is, before FIG. 27.-- Healthy and vigorous root
they begin to leaf out in the system of a youngtung-oil tree.
spring. The transplanting
of trees in foliage has been followed by a slow and unsatisfactory
growth. In the vicinity of Gainesville, in a normal season, trans-
planting should be completed before February 20.

It is essential in digging nursery stock that the major portion
of the taproot be left intact. As with all plants, exposure of the
roots to sun or wind during transplanting should be avoided and
at no time should they be allowed to become dry.

During its first years the young tree evidently requires suffi-
cient cultivation to keep out encroaching grass and weed growth
within a radius of a few feet of the trunk if a maximum growth
is to be attained. Because of the very shallow rooting habit, a
mat of fibrous roots lying just under the soil surface, any cultiva-
tion in close proximity to the trees must be shallow if the root
system is not to be more or less seriously disturbed.







Florida Agricultural Experiment Station


Mulches, of any coarse materials, have shown their value in
keeping down weed growth and in retaining soil moisture during
dry periods.
As a mature size is reached the thick foliage, by cutting off
direct sunlight, tends to discourage grass and weed growth with-
in the shaded areas beneath the trees. This, coupled with the
shallow rooting of the tree, precludes the necessity or desirability
of much cultivation in mature plantings.

PRUNING
Pruning of older trees, other than the removal of dead, broken,
or interfering branches, seems to be of no advantage and un-
necessary. Due to the manner of fruiting, the fruit being borne
only on twig terminals of the previous season's growth, any prun-
ing evidently tends to reduce the number of fruiting twigs with
a consequent reduction of yields.
In nursery stock a great variation is to be noted in the height
at which lateral branching occurs. With some trees this branch-
ing will be relatively low on the stem, while with others no
branching is evident until heights of five or more feet are reached.
Trees of the latter type of branching, if not forced into lower
lateral growth, are later more or less top-heavy and do not seem
to develop as soon into trees with as much fruit-bearing surface
as those with additional lower laterals.
Normal branching of the stem in the tung-oil tree is mostly
in the form of whorls rather than an irregular spacing of
branches at varying heights on the trunk. Efforts to induce the
production of lateral branches by pinching out the terminal bud
have resulted in failure in most cases, as this does not give the
wanted results as obtained with most other trees. It has been
our experience that, instead, the topmost bud or two will shoot
out a vertical growth which extends considerably, sometimes
several feet, above the original pinched-out terminal before it
branches, this still leaving the trunk devoid of laterals for several
feet above the ground.
When transplanting it is highly desirable to have low branch-
ing trees, as they develop more heavy limbs with a higher prob-
ability of greater yields because of greater twig capacity, than
high branching ones with fewer laterals. It is obl\ioully not
possible to know with young unbranched stock at what height it
will eventually branch ^out. As pinching or cutting back the
terminal will not ordinarily force laterals as wanted, the present







Bulletin 221, The Tung-Oil Tree


-.- -,





-. _- .. .*
.. :-




7--- -
itse^: *^^


FIG. 28.-Method of inducing lateral branching in the tung-oil tree. By
removal of bark above bud (left), lower branches were caused to grow on
tree on right.






Florida Agricultural Experiment Station


known solution lies in cutting back the stock severely at the time
of transplanting.
There is one means by which dormant buds on the trunks of
young trees may be forced into growth (Fig. 28). This method
consists in the removal of a horizontal strip of bark from 1/8 to
1/ inch in width and 1 to 11/2 inches in length just above the bud
where a branch is desired. The operation is performed in early
spring, after growth has started, the wound soon healing over
and the resultant branch remaining in active growth. Not hav-
ing been practiced in a large way, the commercial practicability
of this method has not been determined.

FERTILIZER TESTS
Fertilizer tests, inaugurated in 1923 to ascertain the most
efficient fertilizers, indicate the lack of nitrogen to be the limit-
ing factor in growth, and that a complete mixture containing
ammonia, phosphoric acid, and potash gives the maximum
growth and yield. Cover-crops of Crotalaria have been grown
annually in the test plots which will account to some extent for
the behavior of unfertilized (check) trees. All trees were
mulched, once (in 1925) with Japansese cane bagasse and once
(in 1927) with the refuse remaining from Spanish moss after
the fiber is removed. Annual fertilizer applications were made
in early March of each year until 1928, at which time and there-
after the annual amounts were split, one-half being applied in
March and one-half in June.
Results as shown in Table VII cannot be considered as being
final, by any means, as sufficient time has not elapsed since the
inception of the tests. It i's believed, however, that they will be
indicative of the responses to the fertilizers used. Total yields
given should not be construed as the possible maximum due to
the varying fertilizer elements used and the soil on which planted.
The latter, a deep, coarse Norfolk sand, was extremely deficient
in organic matter at the time of planting, due to having been
cropped for several years previous with no return of \eget;able
matter to the soil nor the growing of cover clrop.-.
Bud differentiation occurring during the summer, as shown by
Abbott19, indicates that any season's crop will be dependent in a
large measure on the condition of thrift in the tree the season
prior to fruiting. Large yields, without sufficient available plant
19Abbott, Chas. E. Fruit-Bud Development in the Tung-Oil Tree. Jour.
Agr. Research 38:679-695. 1929.







Bulletin 221, The Tung-Oil Tree


FIG. 29.-Tung-oil trees in fertilizer test plantings. Planted January,
1923. Upper photograph made in November, 1923; lower photograph made
from same relative position June, 1927.

nutrients in the soil to maintain a condition of thrifty growth,
are commonly followed the next season by lowered yields. The
inference is not that the tree will bear heavily only in alternate
years but rather that soil fertility must be maintained to meet the
drain of heavy fruiting and at the same time to sustain a normal
vegetative growth for subsequent satisfactory annual yields.
Owing to losses by leaching in sandy soils it seems advisable
that annual amounts of fertilizers used be split into two applica-
tions; the first being applied in early spring at about the time of
the starting of growth and the second at some time in June.
Some growers have secured a thrifty growth in commercial
plantings from the use of organic fertilizers alone, in proper
quantities.














Fertilizer Material


Nitrate of soda..........
Steamed bone meal.......
4-8-4. SA, 2%; DB, 2%;
SP; MP ........
Superphosphate ..........
Muriate of potash.........
Superphosphate and.....
Muriate of potash.......
Manure. ..............
Check (no fertilizer).......


TABLE VII.-YIELDS* AND MEASUREMENTS OF TUNG TREES IN FERTILIZER TEST PLOTS.

S1927 1928 1929 1 Ar


Pounds
fertilizer
applied
per
tree


Average tree yield Pounds Average tree yield


Single
Type

Ib. Ioz.


Cluster
Type

Ib. oz.


fertilizer
applied


Single
Type

lb. oz.


Cluster
Type

lb. Foz.


Pounds
fertilizer
applied
per
tree


Average tree yield

Single Cluster
Type Type

Ib. oz. lb. oz.


Planted 1922-15 trees to plot


8 1
15 3

12 4
9 2
2 Y3
2
7 Y3
10 20
7 0


3-year average
tree yield

Single Cluster
Type Type


lb. oz.


1929 Average
Tree Measureme

Height Spread


Ib. oz. feet feet


Planted 1923-12 trees to plot

Cottonseed meal and...... 1 Y .. .. .. 2 .. .. 2 .
Steamed bone meal.... 1Y 3 7 5 3 2 3 10 3 10 2 8 13 7 3 .5 5 5 5 10.5 14 15.5
Lime only............... 3 1 12 2 7 0 3 1 3 8 0 5 7 5 3 3 7 3 11 9.9 11.9 12.5
5-8-4. NS, 2%; SA. 1%;
CSM, 2%; SP; P, lime 3 3 0 4 12 4 4 0 4 9 4 8 14 7 10 5 5 5 10 10.7 13.1 15.6
Check (no fertilizer)....... 0 0 14 3 3 0 0 5 3 7 0 1 7 8 1 0 14 4 14 8.1 10.8 11.3
5-8-4 as above (no lime)... 3 4 8 6 11 4 4 12 7 5 4 10 12 15 8 6 11 9 13 11.2 15.1 15.9
Manure................ 20 1 1 4 2 20 1 8 3 15 20 5 12 6 6 2 7 4 13 9.7 12.5 12.8
5-8-4. CSM, 2%; NS, 3%;
SP;MP............... 3 3 4 5 0 4 4 6 6 1 4 8 4 6 15 3 5 6 0 10.9 15.6 15.1
Steamed bonemeal....... 5 1 11 4 15 5 2 5 4 4 5 5 1 9 3 3 1 '6 2 11.1 14.6 14
*All seed weights of air-dried hulled seeds.
SA-sulphate of ammonia; DB-dried blood; SP-superphosphate; MP-muriate of potash; NS-nitrate of soda; CSM--cottonseed meal.


ents

Trunk
Circ.

inches


15
14.4 "

14.7
12.4
14 .

15.8
14.2


0'


''''' "' '


-_-- i 1 1----1----1----1----1 1 .I'


1-- 1--1-1--I "







Bulletin 221, The Tung-Oil Tree


Samples of seed of the 1927 crop were taken from the various
fertilizer plots, as given in Table VII, for the purpose of deter-
mining any differences in oil content under different fertilizer
treatments, and in the "single" and "cluster" types of trees when
given the same kinds and amounts of fertilizers. The analyses
were made by Dr. H. A. Gardner. From Table VIII, which gives
these analyses, it will be noted that for the season in question
there is no apparent definite correlation between any given fer-
tilizer and percentage of oil in the seed.
COVER CROPS
Any leguminous cover crops, grown in the tree middles, are
beneficial in that they increase both the nitrogen and the organic
content of the soil, most Florida soils being more or less deficient
in both. Because of their rank growth, adaptability to various
soils, and relative small cost of seeding, the Crotalarias, both C.
striata and C. spectabilis (C. sericea), are apparently giving the
most satisfaction. The latter species is well adapted to northern
sections of the state. After one planting it has been possible to
obtain volunteer crops in succeeding years without further seed-
ing. With the younger trees the cover crop is confined to the
middles, a strip of a few feet on each side of the trees being kept
clean by occasional shallow cultivation. Other cover crops which
may be used include beggarweed, velvet beans, and cowpeas,
although those varieties of cowpeas subject to nematode attack
should not be planted.
In late fall, or after being killed by frost, the cover crop can
be knocked down and partially covered by going over once with
a disc harrow. No other cultivation then need be given until
spring.
HARVESTING
As far as picking the crop is concerned, the tung-oil fruit may
well be designated a "lazy man's crop". The fruits, ripening in
October and November, fall from the trees as they mature. They
can then be gathered from the ground at any time during the few
weeks following. The seed does not deteriorate as a result of
remaining on the ground for a few weeks.
The whole fruits, after air drying, are marketable as they fall
from the tree, present milling machinery adequately and cheaply
taking care of the separation of the seed from the hull. Hulling
of seed by hand is required only for that desired for planting
purposes,








Florida Agricultural E.pI ri;m( Wf Station


TABLE VIII.-OIL AND MOISTURE CONTENT OF SEEDS FROM TREES UNDER
DIFFERENT FERTILIZER TRE TIMENTS.


Nos.
Fertilizer Clustei
lM...r,,'r. i

Sodium nitrate....... ................ 6.8
Sodium nitrate.........................
Bone m eal........................... 7.8
B one m eal........................ ....
4-8-4St. m 'itl ,r nf w,'i ,, ..Il ,. 'i. |

potash............ ............... 7.2
4-8-4 mixture of a n ... i -l.I .. .
blood, 2% ; ac:dl rl,,,jli Ii. i i ii i ..I
.\. ..1 pl. '.. I .... ... ......... ....... 6 7
A. i ,.. ........................ .. .
M m1 ,r i ..I p., .i I, ................. 7 .4
Muriate of potash ............. ..........
Acid phosphate and muriate of potash... 8.1
Acid phosphate and muriate of potash.....
M anure .............................. 7.7
M anure.............. .. ... ......... .
Checks 'i..I r ; ili.. i. ................ 7.3
Checks I... nill,.. ... ..... ..
Cottonseed meal and bone meal......... 7.1
Cottonseed meal and bone meal..........
Lime (slaked) only ................... 6.8
Lime (slaked) only .................... ..
5-8-4 mixture of sodium nitrate, ammoni-
um sulphate, acid phosphate and muri-
ate of potash, plus lime.............. 6.6
5-8-4 mixture of sodium nitrate, ammoni-
um sulphate, acid phosphate and muri-
ate of potash, plus lime.............. ...
Check........... ................... 8.7
C heck ................. ............. .
Same as No. 11 without lime............ 7.2
Same as No. 11A without lime............
Manure............................. 7.4
Manure ...............................
5-8-4 mixture of cottonseed meal, sodium
nitrate, acid phosphate and muriate of
potash............................ 8.1
5-8-4 mixture of cottonseed meal, sodium
nitrate, acid phosphate and muriate of
potash ........ ..... .............. .
Bone meal only........ .............. 7.6
Bone meal only.................. ... ....


1-16 Nos. 1A-16A
r Type Single Type
Oil l.i.ru Oil

31.2 ... 33.4
6.9 33.4
36.1 .
7.4 35.2


34.1


32.5

35.3

36.9

32.5

33.6

35.1

34.0


31.8


33.1

35.3

32.7


32.9


32.9


32.4

35.1

35.0

31.1

35.2

36.6

32.1

36.9


34.5

30.6

33.8

36.1


35.4

35.1


EXPRESSING THE OIL
A plant for the expressing of oil from the seeds was erected,
equipped, and put in operation by Mr. L. P. Moore near Gaines-
ville in 1928, thus initiating the commercial production of tung
oil in America (Fig. 30).
In equipping the above plant the designing or manufacture of
new types of machinery for hulling and crushing was not required







Bulletin 221, The Tung-Oil Tree


FIG. 30.-Interior view of tung oil expressing plant located near
Gainesville. (Courtesy Alachua Tung Oil Corp.)

as it was found possible to satisfactorily adapt hullers and crush-
ers used for such work on other products. The whole fruits,
after thorough air drying, are first decorticated by a combined
huller-separator which in the process removes both the outer hull
and most of the hard seed coat pelliclee), these waste products
being removed and separated from the seed kernels by air suction.
The seeds, by means of conveyors, are then passed through a
grinder and then fed into an expeller. The expeller, by exertion
of tremendous pressure, expresses the oil, separating it at the
same time from the residue or pomace. After settling, no further
treatment is needed, the oil then being ready for market and use.
The capacity of the plant is approximately 50 gallons of oil
per hour, and is believed to be adequate to take care of the pro-
duction of several thousand acres of tung trees. Through the
medium of this plant the grower is offered a ready outlet for
his crop.

PRODUCTS

The principal product of the tung-oil tree is the oil, which is
expressed from the seed. The amount of oil in the seed varies
from 32 to 39 percent by weight. Oil of fair quality is light golden







Florida Agricultural Experiment Station


or light amber in color and, when free from impurities and of
good quality, is nearly transparent. As a rule, not more than
three pounds of seed are required for the production of a pound
of oil.
The standard requirements for raw tung oil, as published by
the American Society for Testing Materials and approved by the
Paint Manufacturers' Association of the United States and the
National Varnish Manufacturers' Association of the United
States20, are given below:
Maximum Minimum
Specific gravity at 15.5C. .............. 0.943 0.939
Acid number (alcohol-benzol) ........... 7.0
Saponification number ................. 195.0 190.0
Unsaponifiable matter, percent .......... .76
Refractive index at 250C ............... 1.520 1.515
Iodine number (Wijs) ................. ..... 163.0
A. S. T. M. heating test, minutes......... 12.0 ...

A comparison of Florida tung-oil to the above standards
demonstrates the high quality of the Florida product. The fol-
lowing analyses were made by Dr. H. A. Gardner21:

Cold pressed Florida
Fla. No. 1 No. 2
Appearance and color ......... Pale and clear Pale and clear
Spec. gravity at 15.5C......... 0.941 0.944
Acid number .................. 0.5 1.0
Saponification number ......... 193.8 194.4
Refractive index ............... 1.519 1.5175
Iodine number ................. 166.0 161.0
A. S. T. M. heat test............ 10% 9%

Oil produced from Florida grown seeds is of very high and
satisfactory quality. It has an excellent color, being much paler
and clearer than the imported product. Dr. Gardner, in 1928,
distributed Florida tung oil to some 80 varnish manufacturers
for varnish-making tests. He writes "Practically every one of
these manufacturers reported the American oil to be superior to
imported oil. It is quite clear from the reports of the results
obtained that American oil is entirely satisfactory and generally
superior to imported oil. To quote examples, one maker reported
a slight improvement in color of his finished varnish when made
with American-grown oil; another reported that American oil
gave a faster bodying action in the kettle, producing a paler,
20Submitted by Henry A. Gardner, of the Institute of Paint and Varnish
Research, and taken from Miscellaneous Series, No. 125, Department of
Commerce.
21Gardner, Henry A., Scientific Section, American Paint & Varnish Manu-
facturers' Association, Circular 205, June, 1924,






Bulletin 221, The Tung-Oil Tree


clearer varnish with a somewhat faster and harder drying film
and with better hot water resistance; another reported that the
American oil made tougher and more elastic varnishes with
better water resistance, etc. There seems no doubt about the
fact that American-grown tung oil will be acceptable to the indus-
try. At no time has a sample of oil been found to give abnormal
properties."
The by-products, remaining after oil extraction, consist of
the hulls and pomace. The former contains little nitrogen but
some potash and is probably of value both as a mulching material
and for the potash contained. The latter, the residue of the seed
remaining after oil extraction, contains nearly 6 percent nitrogen
and in this respect compares favorably with castor pomace which
is widely used as an organic source of nitrogen in fertilizers.

DISEASES AND INSECT PESTS

It appears that the tung-oil tree, during its introduction to
America, has not been accompanied by any of the insects or
diseases which may affect it in its native Chinese home. Few
plants of economic importance have been imported from foreign
countries without the importation with them of some of their
diseases or insect enemies. If the tung-oil tree has left its natural
enemies behind, it is indeed a fortuitous circumstance and one
which lends encouragement to the view that its culture can be
made profitable in America.
However, no growing plant of any kind is known to be entirely
immune to the attacks of parasites, either insect or fungus. It is
naturally expected, therefore, that when a plant is introduced
into a new country the insects and other plant parasites already
there will in some measure adapt themselves to the new plant.
This is apparently taking place in the case of the tung-oil tree
in Florida. Up to the present time one root parasite, the
nematode, one fungus disease, the thread blight, and one bacterial
disease, a leaf spot, have been found attacking it. The tree is
also a host to three species of scale insects-the latania, cottony
cushion, and ivy scales. Although it is possible that with a large
increase in commercial plantings some spraying will be neces-
sary it has not been the case to date. It is seldom that any in-
.iurioi- insects or diseases are seen, even in small quantity, on
these trees except perhaps root-knot which is found mainly on
nursery stock that has been planted on infested soils.






58 Florida Agricultural Experiment Station
NEMATODE
(Heterodera radicicola (Atkinson))
In the case of tung-oil nursery trees, grown on old cultivated
land at the Experiment Station at Gainesville, the roots of a con-
siderable number have been found infested in varying degrees
with nematode. This parasite causes the trouble known as root-
knot. Trees so affected were observed for the first time on
February 24, 1923. Root-knot affected roots of a tung-oil tree are
shown in Figure 31. In some cases, particularly in fields known
to be heavily infested, the effect of the nematode has been pro-





.- .7


-. :.. .
.
\.. -- .
.. : .
."-"-2i- 2

.


iT ~,


FIG. 31.-Roots of young tung-oil tree severely affected with nematode
root-knot. Compare with healthy roots shown in figure 27.


~SCf~






Bulletin 221, The Tung-Oil Tree


nounced; young seedlings have failed to make a normal growth,
while in other cases they apparently have been killed. This trouble
has not been perceptible where the seed were planted in new land
or in land which had been in grass for one or two seasons pre-
viously.
Strict rejection of all nursery trees showing nematode infesta-
tion at digging time, coupled with the planting of groves on newly
cleared land or on land that has not grown hosts of the nematode
for two or three seasons previously, would seem an adequate
measure for preventing serious losses from this parasite.
Perhaps it would be well, as an added measure of safety, to grow
as cover crops in tung-oil tree groves only those plants known to
be immune to or highly resistant to the nematode; such as Crota-
laria, beggarweed, and velvet beans.
It is not felt that the effects of the nematode upon tung-oil
trees under the conditions cited will prevent the successful growth i
of these trees in Florida. The nematode attacks a great number
of trees and plants22, and some of those which are subject to
rather heavy attack are, by using proper precautions, grown with
profit. The very, fact that the susceptibility of the tung-oil tree
to root-knot is known makes it possible to take precautions
against this trouble. For more complete information concerning
nematodes and their control the reader should consult bulletins
136 and 159, by J. R. Watson, of this Station.

COTTONY CUSHION SCALE
(Icerya purchase Mask.)
In January, 1923, this scale-insect (Fig. 32) was found on tung-
oil trees in the Experiment Station grounds and since has been
found from time to time on both young and old tung-oil trees
there. Severer infestation has not appeared upon the tung-oil
trees than upon other host plants of the scale, such as citrus,
growing in the same vicinity.
The cottony cushion scale is not viewed with any particular
alarm by Florida horticulturists, owing to the readiness with
which it is controlled by the Australian lady-beetle and there is
no likelihood that it will be any more injurious to tung-oil trees
than it is at present to citrus and many shade and ornamental
trees23. However, when nursery trees are found infested with it
22A comprehensive list of the host plants of nematodes will be found in
Circular 50 of the State Plant Board.
28A list of host plants of cottony cushion scale will be found in Circular
50 of the Florida State Plant Board.







Florida Agricultural Experiment Station


FIG. 32.-Cottony cushion scale, Icerya purchase Mask, on tung-oil
leaves and stem.

at digging time, all the trees should be scrubbed thoroughly with
a solution of whale-oil soap; otherwise, more or less isolated grove
plantings may experience a severe increase of the scales before
the latter are found by the lady-beetle.


LATANIA SCALE
(Aspidiotus lataniae Sign.)

This scale-insect (Fig. 33), which is of quite common occur-
rence on palms and Australian pines24 in Florida, has been found
in small quantities on tung-oil trees. Its economic importance is
questionable. It can be controlled easily by proper spraying
practices and frequently is kept well under control by parasites.


2'Casuarina sp.







Bulletin 221, The Tung-Oil Tree


DISEASES
Thread blight, a fungus dis-
ease attacking many plants in
Florida, has been found on
both the tung-oil and mu-oil
trees. Thus far it has been
seen on these trees only in rare
instances. Full details as to
its appearance and control are
to be found in Bulletin 186"2
of this Station.
A bacterial leaf spot26 has
been reported as affecting the
foliage of tung-oil nursery
trees in Georgia. No infec-
tions showing marked injury
were found on trees four years
of age or older.

CONDENSED
INFORMATION
Imports of tung oil into the Fir. 33.-Latania scale, Aspidiotus
United States in 1929 amount- lataniae Sign, on Chinaberry, Melia
United States in 1929 amount- azadarach. (After Wilson, Quarterly
ed to 119,677,718 pounds, with Bul. State Plant Board of Florida,
a valuation of $14,972,084. Vol. II, No. 1.)
Tung oil, or wood oil, is the oil expressed from the seeds of
the tung-oil tree, Aleurites fordi, and mu-oil tree, A. montana.
The tung-oil tree is the only one being grown in Florida for
commercial oil production, although other species of Aleurites
are growing in the state.
Florida's first tung-oil tree was planted at Tallahassee in 1906.
The original tree is still living.
The present tung-oil acreage in Florida is approximately 5,000,
the greater portion being in Alachua, Clay, and Levy counties.
Favorable reports on the growth of the tree have been received
from many of the northern and northwestern counties but not
from any of the more southern ones.
The tree is now being grown on several soil types, it apparently
thriving best on soils having an acid reaction.
"2Weber, G. F. Thread Blight. Florida Agr. Exp. Sta. Bul. 186. 1927.
26Boyd, O. C. A Bacterial Disease of Tung-Oil Tree. Phytopath. 20:756-
758. 1930.







Florida Agricultural Experiment Station


Excesses of lime and phosphate in the soil'have proven detri-
mental to tree growth.
Thorough drainage of soils is necessary.
The growing of summer leguminous cover crops in the tree
middles is recommended.
SComplete fertilizers, containing ammonia, phosphoric acid, and,
potash, have shown the best results in yield and tree growth.
Manures also are valuable fertilizers.
No varieties have as yet been definitely separated and des-
ignated as such. An apparent varietal difference, having to do
with the number of fruits borne on twig terminals, has led to
the tentative designation of "single" and "cluster" types or
varieties.
Average yields on Station plots over a three-year period have
been higher from the "cluster" trees. The highest individual
yield has been from a "single" tree. Averages show seeds from
"cluster" trees to be somewhat.smaller or lighter in weight than
those from "single" trees.
Ten 16-year-old trees on Station plantings have yielded in eight
years (ninth to sixteenth years inclusive) an average of 22
pounds 5 ounces of hulled seeds per tree per year.
Low branching in the tree can be induced by severe cutting
back or by the removal of a strip of bark above a bud where a
branch is wanted.
Propagation is by seeds. Budding can be accomplished if
found to be desirable.
An oil expressing plant has been erected and put in operation
in Alachua County.
Tung oil expressed from Florida-grown seeds has proved to be
of high quality.
Analyses of the press cake and hulls show them to have a
potential value as fertilizers.
A bushel of seeds in the hull contains approximately 1,900
seeds.
One hundred pounds of fully matured and thoroughly dried
fruits consist of about 56 pounds of seed and 44 pounds of hulls.
An average of 140 thoroughly air-dried seeds, of the 1927 crop,
were required to weigh one pound.
A bushel of air-dried whole fruits weighs approximately
303/ pounds; the same quantity of air-dried hulled seeds weighs
approximately 42 pounds.







Bulletin 221, The Tung-Oil Tree 68

The percentage, by weight, of the oil in the seeds varies from
32 to 39 percent, the average being about 33 1/3 percent.
Pure tung oil weighs slightly under 8 pounds to the gallon.
With imported oil, in converting pounds to gallons, or vice versa,
the U. S. Department of Commerce uses a figure of 71/2 pounds
to the gallon.

ACKNOWLEDGMENTS

The writers are indebted to Dr. K. F. Kellerman, Dr. David Fairchild,
and Mr. R. A. Young, all of the Bureau of Plant Industry, United States
Department of Agriculture, for information generously supplied from the
files of that department, particularly as related to the introduction and dis-
tribution of Aleurites trees in the United States; to Dr. H. A. Gardner, of
the Scientific Section of the Paint and Varnish Manufacturers' Associations,
for various analyses and items of technical information; to Mr. B. F. Wil-
liamson, of Gainesville, for notes on the tung-oil tree; to Mr. G. B. Merrill,
of the State Plant Board, for identification of insect specimens; to Mr. Ed.
L. Ayers for various notes, references, and photographs; to Dr. A. F. Camp,
of the Experiment Station, for several photographs; and to the Alachua
Tung Oil Corporation for information relative to their tung oil expressing
plant at Gainesville.




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