Bulletin 280 (A revision of Bulletin 221) June, 1935
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
WILMON NEWELL, Director
THE TUNG-OIL TREE
R. M. BARNETTE
A. F. CAMP and
R. D. DICKEY
Fig. 1.-Tung oil planting at the Florida Experiment Station photo-
graphed in the fourth year after planting.
Bulletins will be sent free to Florida residents upon application to the
AGRICULTURAL EXPERIMENT STATION
EXECUTIVE STAFF BOARD OF CONTROL
John J. Tigert, M.A., LL.D., President of the Geo. H. Baldwin, Chairman, Jacksonville
University A. H. Blanding, Bartow
Wilmon Newell, D.Sc., Director A. H. Wagg, West Palm Beach
H. Harold Hume, M.S., Asst. Dir., Research Oliver J. Semmes, Pensacola
Harold Mowry, M.S.A., Asst. Dir., Adm. Harry C. Duncan, Tavares
J. Francis Cooper, M.S.A., Editor J. T. Diamond, Secretary, Tallahassee
Clyde Beale, A.B.J., Assistant Editor
Jefferson Thomas, Assistant Editor
Ida Keeling Cresap, Librarian BRANCH STATIONS
Ruby Newhall, Administrative Manager
K. H. Graham, Business Manager NORTH FLORIDA STATION, QUINCY
Rachel McQuarrie, Accountant
Rachel McQuarrie Accountant L. 0. Gratz, Ph.D., Plant Pathologist in
MAIN STATION, GAINESVILLE R. Kincaid, Ph.D., Asso. Plant Pathologist
J. D. Warner, M.S., Agronomist
AGRONOMY R. M. Crown, B.S.A., Asst. Agronomist
W. E. Stokes, M.S., Agronomist** Jesse Reeves, Farm Superintendent
W. A. Leukel, Ph.D., Agronomist
G. E. Ritchey, M.S.A., Associate* CITRUS STATION, LAKE ALFRED
Fred H. Hull, Ph.D., Associate John H. Jefferies, Superintendent
W. A. Carver, Ph.D., Associate Geo. D. Ruehle, Ph.D., Associate Plant
John P. Camp, M.S., Assistant Pathologist
W. A. Kuntz, A.M., Assoc. Plant Pathologist
ANIMAL HUSBANDRY B.R. Fudge, Ph.D., Associate Chemist
A. L. Shealy, D.V.M., Animal Husbandman** W. L. Thompson, B.S., Asst. Entomologist
R. B. Becker, Ph.D., Dairy Husbandman
W. M. Neal, Ph.D., Associate in Animal EVERGLADES STATION, BELLE GLADE
D. A. Sanders, D.V.M., Veterinarian A. Daane, Ph.D., Agronomist in Charge
M. W. Emmel, D.V.M., Asst. Veterinarian R. N. Lobdell, M.S., Entomologist
W. W. Henley, B.S.A., Assistant Animal F. D. Stevens, B.S., Sugarcane Agronomist
Husbandman G. R. Townsend, Ph.D., Assistant Plant
P. T. Dix Arnold, B.S.A., Assistant Dairy Pathologist
Husbandman J. R. Neller, Ph.D., Biochemist
R. W. Kidder, B.S., Assistant Animal
CHEMISTRY AND SOILS Husbandman
Ross E. Robertson, B.S., Assistant Chemist
R. W. Ruprecht, Ph.D., Chemist**
R. M. Barnette, Ph.D., Chemist SUB-TROPICAL STATION, HOMESTEAD
C. E. Bell, Ph.D., Associate
R. B. French, Ph.D., Associate H. S. Wolfe, Ph.D., Horticulturist in Charge
H. W. Winsor, B.S.A., Assistant W. M. Fifield, M.S., Asst. Horticulturist
H. W. Jones, M.S., Assistant Stacy 0. Hawkins, M.A., Assistant Plant
C. V. Noble, Ph.D., Agricultural Economist** WEST CENTRAL FLORIDA STATION,
Bruce McKinley, A.B., B.S.A., Associate BROOKSVILLE
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Assistant E. W. Sheets, D.Agri., Animal Husbandman
ECONOMICS, HOME W. F. Ward, M.S.A., Asst. An. Husbandman*
Ouida Davis Abbott, Ph.D., Specialist**
L. W. Gaddum, Ph.D., Biochemist FIELD STATIONS
C. F. Ahmann, Ph.D., Physiologist
J. T. Hall, Jr., B.S.Ch.E., Asst. Physiologist Leesburg
ENTOMOLOGY M. N. Walker, Ph.D., Plant Pathologist in
J. R. Watson, A.M., Entomologist** W. B. Shippy, Ph.D,. Asso. Plant Pathologist
A. N. Tissot, Ph.D., Associate K. W. Loucks, M.S., Asst. Plant Pathologist
H. E. Bratley, M.S.A., Assistant J. W. Wilson, Ph.D., Associate Entomologist
J. W. Kea, B.S.A., Assistant C. C. Goff, M.S., Assistant Entomologist
HORTICULTURE Plant City
A. F. Camp, Ph.D., Horticulturist* A. N. Brooks, Ph.D., Plant Pathologist
G. H. Blackmon, M.S.A., Horticulturist R. E. Nolen, M.S.A., Asst. Plant Pathologist
A. L. Stahl, Ph.D., Associate Cocoa
F. S. Jamison, Ph.D., Truck Horticulturist A.S. hoads, Ph.D., Plant Pathologist
R. J. Wilmot, M.S.A., Specialist, Fumigation
R. D. Dickey, B.S.A., Assistant Horticulturist A.H. Eddins, Ph.D., Plant Pathologist
PLANT PATHOLOGY Monticello
W. B. Tisdale, Ph.D., Plant Pathologist** G. B. Fairchild, M.S., Assistant Entomologist
George F. Weber, Ph.D., Plant Pathologist
R. K. Voorhqes, M.S., Assistant Bradenton
Erdman West, M.S., Mycologist David G. Kelbert, Asst. Plant Pathologist
Lillian E. Arnold, M.S., Assistant Botanist
In cooperation with U.S.D.A. E. R. Purvis, Ph.D., Assistant Chemist,
"* Head of Department. Celery Investigations
Introduction --------.............. --..--..-------.-.......----- 5
Description of the Tree -.. ..- --------------- .-------........... 7
Relationships and Adaptability ...--..---...-..--- .... --...--.-.....--...- 12
The U ses of Tung Oil.... ..-.......-....-.... .... ...... ........ ............ ................. 18
Imports of Tung Oil into the United States..-------....-.....-.........---. 20
The W ood-oil Industry in China..................... ----....... ............ 20
Introduction of the Tree into the United States...-.. ...-. ----....... ...---- -. 25
Plantings of the Florida Experiment Station....---.....-.....--..--- ....... 26
Other Early Florida Plantings-......... -----.........----- ------ 30
Acreage and Distribution............... ------------------..... 34
Varieties --. ------ -----------....---.. .......... ...................... 35
Soils -----..... ------------- --.-----------------..........-- 39
Bronzing ...... .. ........................ ......... 41
Drainage ---..................... -- ......--. ----...........---------. 46
Propagation ..... ---- .---------------.. .............. ...... 46
Culture..-.............-----......... ......... --- ------------ 50
Transplanting and Cultivation........ .......... ......--. 50
Pruning ...... .. .------....... ......52
Fertilizer Tests.......... ............. ............ . ........ ................. 55
Cover Crops ........... .....-.......... .......------- --.. 61
Harvesting ......--.....- ................... 61
Expressing the Oil --. .......- .......---- 62
Products --...-- ......................... ---......... 63
Condensed Information ... --- ......... ......... ..... ------- 65
Acknowledgements -- -- -----.........------------.... ...---...-... ..--- 66
Literature ..........- .... .... ....... . ---- -- -------- 66
In 1924 Bulletin 171 (13)1 of this Station was published,
giving the then known information on the tung-oil tree and its
culture in Florida. In 1930 Bulletin 221 (14) was published and
included the information in Bulletin 171 and the additional in-
formation accumulated in experimental work and in the develop-
ment of the industry commercially up to that time. Bulletin 221
is here revised to include such additional information as has be-
come available since the original date of publication. This revi-
son conforms closely to Bulletin 221 with the exception of the
1Figures in parentheses (Italic) refer to the list of literature in the
back of this bulletin.
THE TUNG-OIL TREE
R. M. BARNETTE
A. F. CAMP and
R. D. DICKEY
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 var-
nishes 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 constitu-
ents. Its use in paints and varnishes is of comparatively recent
development and its consumption is increasing. According to
David Fairchild (6), the varnishes made with this oil and south-
ern rosin, as two of the constituents, are superior to those made
with the high-priced and rapidly disappearing gums, such as
kauri, Manila, and Zanzibar.
The rather excellent showing made by bearing tung-oil trees
on the Experiment Station grounds and in later commercial
plantings, together with the Station's demonstration of the rela-
tive ease with which the young trees may be grown in the nurs-
ery, has attracted the attention of horticulturists as well as of
manufacturers who have occasion to use tung oil in their opera-
tions. This also has raised, quite naturally, the question as to
whether it is possible to produce tung oil profitably in this
country. Conditions in China make an assured and adequate
supply of oil from that country more or less uncertain. The im-
ported oil is frequently inferior in quality or adulterated, and
prices, therefore, are subject to sudden changes. An American
source of supply is much to be desired and, if such can be devel-
Fig. 2.-Tung-oil trees in bloom on the grounds of the University of Florida Experiment Station at Gainesville.
Planted in 1912 and 1914.
The Tung-Oil Tree 7
oped, it will doubtless go far toward stabilizing and insuring
the future welfare of the paint and varnish industries, as well
as furnishing an income-producing 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
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,
though 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 blossoms usually make their appearance slightly in ad-
vance of the leaves. At Gainesville the first blossoms appear at
any time from late February to April 10, depending upon the
season. The flowers are borne in clusters, each blossom being
white and tinged or striped with pink in the throat. The flowers
of the tung-oil tree are not perfect but are unisexual. Stamens
and pistils are produced in separate flowers but both flower
types are borne on the same tree monoeciouss). They are borne
in large, loose cymes at the terminals of twigs of the previous
season's growth (Fig. 3). The pistillate flower, if present, is
borne as the central or apical flower of the cyme and all lateral
flowers are staminate, except in trees of the so-called cluster
type wherein one to several pistillate flowers are produced
laterally in a single flower cluster.
Apparently pollination is amply provided, since the pistillate
flowers are surrounded in the cluster by staminate ones at an
approximate ratio of 60 to 1. Because of the preponderant pro-
portion of staminate blossoms and the cymose type of flower
arrangement, it is possible that there is much more self-or close-
pollination in trees than cross-pollination among them. This in
part may account for a fairly large proportion of seedlings close-
ly resembling the parent.
In three instances, one on each of three trees, individual
flowers have been found having both stamens and pistil (perfect
or hermaphrodite flowers). No special significance can be at-
tached to such flowers because they are so rare, and besides, no
pollination troubles have ever been reported. Were there iso-
lated plantings of a single budded variety, it is possible that
Fig. 3.-Flower cluster of Aleurites fordi. Note that all blossoms shown in cluster are staminate ones
except the one in upper center.
The Tung-Oil Tree 9
effective pollination would be hindered but such a condition is
not believed probable since no trouble has been experienced in
the setting of fruit from blossoms that were hand-pollinated
with pollen from the same tree.
Fig. 4.-Flowers of the tung-oil tree, Aleurites fordi; pistillate (female)
flowers above; staminate (male) flowers below.
Another floral difference noted and found to be transmitted
to the seedlings is the absence of the internal pink or reddish
coloration on the petals in the throat of the flower. The occa-
sional trees with wholly white or faintly yellow blossoms seem-
ingly do not differ in other respects from the ordinary seedling.
10 Florida Agricultural Experiment Station
1 2 3 4 5
Fig. 5.-Variations in size and external appearance of typical mature
fruits of different seedling trees. The numerals correspond to the tree
numbers of Table 2 (p. 28). The internal characters of the same fruits
are shown in Fig. 6.
1 2 4 5
Fig. 6.-Variations in size and internal appearance of typical mature
fruits of different seedling trees. The numerals correspond to the tree
numbers of Table 2 (p. 28). The external characters of the same fruits
are shown in Fig. 5. All fruits shown contain 5 seed, though this number
may vary from 4 to 7 on the same tree.
The fruit (Figs. 5, 6 and 7) is from two to three inches in
diameter, dark olive green in color, turning 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. 18). Each fruit consists of an
The Tung-Oil Tree 11
outer portion or husk, containing ordinarily from three to seven
firm brown seeds (Fig. 8). The individual seeds in shape and
color remind one of very large castor beans. 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 har-
vesting consists in simply gathering the fallen fruit whenever
convenient. The ripe fruit commences to fall in October and
all is off the trees by the middle of December.
Fig. 7.-Extremes in size and shape of fruits from different seedling trees.
The following description of the genus Aleurites is given by
L. H. Bailey in "Manual of Cultivated Plants:"
"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
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."
12 Florida Agricultural Experiment Station
Fig. 8.-Seed of Aleurites fordi after removal from the Truit, i. e., after
being "husked" or "hulled." These are about the natural size.
RELATIONSHIPS AND ADAPTABILITY
The tung-oil tree belongs to the Spurge family-EUPHOR-
BIACE1AE. There are about 4,000 species, divided among some
220 genera, in this family, some of the familiar plants being
Phyllanthus, 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
1 2 3
Fig. 9.-Fruits and seeds of three Aleurites species now growing in
Florida. 1. A. moluccana; 2. A. montana; 3. A. fordi. Normal fruits
contain 2, 3 and 5 seeds, respectively.
The Tung-Oil Tree 13
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 only in the warmer
sections of the state.
Aleurites fordi Hemsl. Tung-oil tree. Wood-oil tree. Tung-
shu. Tung-yu shu. This species, a native of central and west-
ern China, is the principal source of the tung oil or wood oil of
Fig. 10.-Aleurites montana, the mu-oil tree, in bloom at Gainesville.
14 Florida Agricultural Experiment Station
commerce 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
S apex of petiole prominent and cupped;
Jf.a flowers pure white; ovary 3-celled;
fruit 11/2 to 2 inches in diameter,
distinctly 3-angled with prominent,
SIirregular veining on surface, hull
very hard; seeds normally 3, brown,
smooth. (Figs. 10, 11 and 12).
This is the prevailing species in
Fig. 11. Cross-sec- southern China, although both it and
tion of Aleurites mon- A. fordi are said to be found together
tana fruit. 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 is considerably less hardy, however,
being damaged by low temperatures not affecting the latter. The
cold damage sustained, as with the tung-oil, depends mainly on
the 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 tem-
peratures during their first years, but in January of 1928 (in
their fifth year from seeds) they withstood 15 degrees Fahren-
heit with very slight damage. In December of 1934 they were
subjected to a temperature of 160, apparently without damage.
The trees were fully dormant at the time of the cold, having been
defoliated in an earlier frost, and this reduced the susceptibility
to cold damage materially. The above trees bloom profusely but
have set so little fruit that they could be of comparatively little
commercial value. Crosses were made in 1927 by Dr. W. A.
Carver, associate agronomist at this Station, between A. mon-
tana and A. fordi, the former species being used as the male
parent. The hybrid seedlings have so far failed to bear satis-
The oil of A. montana is reported as being chemically the
same as the oil of A. fordi and is reported as making up a portion
of the shipments of China wood-oil.
The Tung-Oil Tree 15
Aleurites moluccana Willd (A. tribola, Forst.) (2). Lum-
bang. Kukui. Candlenut. Varnish tree. Tree with large
spreading branches; leaves large, ovate-acuminate, short-lobed,
rusty pubescent below; paniculate cymes 4-5 inches long of many
small flowers; stamens 15-20; ovary 2-celled; fruit 2-3 inches
Fig. 12.-Leaf and
of Alenrites mon-
16 Florida Agricultural Experiment Station
thick; seeds large, rough and walnut-like. Probably native of
Malay region but now widely cultivated 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, chop-
ped 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 possible
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 re-
quired with this species.
Comparative analyses of seeds of this species and A. fordi
were made by the Station's Department of Chemistry (17). The
results are given below: A. moluccana A. fordi
Meat (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
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, Brevard, and other southern
counties but specimen plants did not survive the cold of Alachua
and Hillsborough counties. In southern Brevard County, on
Merritt's Island, the candlenut has shown an exceptionally vigor-
ous 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. (2). Japan wood-oil tree. Twenty-
five to 30 feet high; leaves broadly ovate, acuminate, 3-5 lobed
or toothed; petals oblong, % inch long, hairy at base; stamens
8-10; ovary 3-4 celled; fruit warty; seeds about the size and
shape of castor beans. Cultivated in Japan south of 400 latitude
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
A tree of this species has fruited in central Polk County, but
small seedlings were killed outright by winter temperatures pre-
The Tung-Oil Tree 17
vailing at Gainesville. In considering the merits of the Japan
wood-oil tree as compared with those of tung-oil tree, the former,
with the little present knowledge as to its behavior under Florida
conditions, offers but little commercial promise.
Fig. 13.-Aleurites moluccana tree growing in Brevard County.
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 made a fair growth in Dade
and Palm Beach counties.
18 Florida Agricultural Experiment Station
THE USES OF TUNG OIL
In China, tung oil has been used for many centuries and is
today 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 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 in-
stead 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 shavings (20).
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,
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
linings 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.
Extensive research on the problem of substituting tung oil
for linseed oil in ordinary paints seems to be resulting in an in-
creased use for this purpose. Raw tung oil cannot be used for
this purpose but must be processed. The tung oil paints give a
The Tung-Oil Tree 19
much glossier finish than ordinary paints, much like enamel, and
seem more resistant to fungus attack, so common in the South-
ern states. These paints, if extensively developed, would be
likely to expand greatly the market for tung oil.
TABLE 1.-TUNG-OIL IMPORTS INTO THE UNITED STATES,
Year Pounds Value per pound
1921 ..... ................. ....... 27,249,000 $ 2,470,000 $0.0906
1922 ................................... 79,089,000 7,891,000 0.0998
1923 ................. ............. 87,292,000 13,397,000 0.1535
1924 .............................. 81,588,000 11,092,000 0.1360
1925 .................................. 101,554,000 11,386,000 0.1121
1926 ................................. 83,004,000 9,148,000 0.1102
1927 .............................. 89,650,000 11,810,000 0.1317
1928 ..............................- 109,222,000 13,419,000 0.1229
1929 ................................... 119,678,000 14,972,000 0.1251
1930 ....... ................... ..I 126,323,000 12,487,000 0.0988
1931 ....................... ........I 79,311,000 4,426,000 0.0558
1932 ................................... 75,922,000 3,434,000 0.0452
1933 ................................. 118,760.000 4,833,000 0.0406
Importations by Months, 1929
I Average price
Month Pounds Value per pound
January ............................ 10,276,734 $ 1,309,187 $0.1273
February ......................... 7,097,159 876,941 0.1236
March ..............-... ......... 8,811,711 1,105,030 0.1254
April ...............-........... 7,294,973 917,222 0.1257
May .................. ........I 9,475,302 1,181,607 0.1247
June .......... -........... ..... 10,491,890 1,304,289 0.1243
July ............................. 14,282,385 1,784,890 0.1249
August ................-....... 9,608,508 1,167,088 0.1214
September ..-............ 16,593,454 2,115,364 0.1275
October ............................ 12,376,707 1,555,166 0.1257
November ........................ 6,035,560 740,395 0.1227
December ...................... 7,333,335 914,905 0.1248
Importations by Months, 1934
January ...................-......[ 10,644,878 $ 570,840 $0.0536
February .................... 6,268,252 309,155 0.0493
March .......................... 6,042,139 340,970 0.0564
April .............................I 12,456,830 676,071 0.0542
May ........................... 7,678,480 435,689 0.0567
June .................. ............. 4,708,190 289,651 0.0615
July .................................... 12,066,647 785,341 0.0650
August ............ ............... 4,140,908 288,683 0.0697
September ...................... I 12,044,668 780,971 0.0648
October ............... ...... 16,024,548 1,079,345 0.0673
November ................ 9,665,323 693,351 0.0717
Eleven months ending
November, 1934 ............. 104,839,683 6,469,648 0.0617
1 Statistics furnished by the Bureau of Foreign and Domestic Commerce,
U. S. Department of Commerce.
20 Florida Agricultural Experiment Station
IMPORTS OF TUNG OIL INTO THE UNITED STATES
In Table 1 are given the statistics on the importation of tung
oil into the United States from 1921 to 1933, inclusive. The rise
in imports is less marked than indicated, since the 1921 imports
were unusually low (in 1918 approximately 42,000,000 pounds
were imported). The decline in 1931 and 1932 was consistent
with the general decline in industry; this decline was also re-
flected in the average value, (see Table 1A, information for
which was furnished by the Oil, Paint and Drug Reporter, New
TABLE 1A.-TUNG OIL PRICES PER POUND, PACIFIC COAST, TANK CARS1.
1928 1 1929 | 1930 | 1931
High I Low | High | Low I High I Low I High I Low
January ........ .15% .13% .14 .13% .11% .10% .06% .06
February ....... .15 .14% .13% .12% .10% .09% .06 .05%
March ............ .13 .121/4 .131/ .12% .10% .09 .06% .06
April ............ .13% .12% .13% .13 .10 .09% .05% .05%
May ............. .13% .12% .13% .13% .09% .08% .05% .05%
June ...............13 .12% .13% .12% .08% .07% .05% .05%
July ............... 141/ .12% .13% .13 .07% .07% .06% .05%
August ............14% .13% 1 .13% .12% .08 .08 .06 .05%
September ...... .13% .13% .14% .12% .07% .07% .06% .05%
October ..........- .14% .13% .14 .13% .06% .05% .06 .05%
November ...... .13% .13 .13% .12% .05% .05% .06% .06
December ........ 13% .13 .12% .12 .05% .05% .06 .05%
Year ................ .15% .121/ .14% .12 .11% .05% .06% .05%
1932 | 1933 1934
S High I Low I High Low I High Low
January -........ .06 .05% .04% .04% .06% .06%
February ....... .06% .05% .04% .04% .07% .06%
March ........... 06% .05% .04% .04% .07% .07%
April .............. .05% .05 .05 .04 .08 .07%
May ................ .04% .04% .05% .05 .08% .07/2
June ...........-.. .05% .04% .06% .05% .08% .08
July .................. .04% .04% .08% .07 .08% .08%
August ............ .05% .04% .07% .06% .09A .08%4
September ..... .05% .05 .07% .06% .09-O .09ao
October .......... .05 .04% .06% .06% .08- .08m
November ....... .04%7 .04% .07% .07% .081 .08
December ........ .04% .044 .07 .0614 .0810 .08A
Year ................ .06% .041% .08% .04 .097T- .06%7
1Courtesy of Oil, Paint and Drug Reporter, New York.
THE WOOD-OIL INDUSTRY IN CHINA
Although accounts of the wood oil industry in China are to be
found 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-
The Tung-Oil Tree 21
ture and to a bulletin entitled "China Wood Oil" (19) issued by
the Department of Commerce for information as to the industry
in China. The information given under this head is taken main-
ly 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 var-
nish, 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 companies. 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 40 F. (this doubtless
refers to A. fordi only), but that young trees with the sap flow-
ing may be injured or killed by a sudden fall in temperature to
18 or 200 F."
It is said that the trees in China may attain a height of from
10 to 30 feet and the trunks a diameter of from 6 to 10 inches,
and that they commence to bear when from three to six years
old, yielding from 30 to 40 pounds of fruit to the tree annually.
Exact information on the methods of production and the age and
size of the trees is not readily obtainable. A recent Chinese
writer (22) reports on the cultivation of the "3 year" tung, stat-
ing that the name is derived from the fact that the trees come
into bearing in three years and usually bear about three crops,
being cut down for firewood about the seventh year. According
to his report the trees bear a small crop at the third year and in-
creasing crops during the fourth, fifth and sixth years and then
rapidly decline in yield and oil content of the seed though the
period of good production may be extended on unusually good
soils. The trees are usually cut down in their seventh year, how-
ever, and the ground allowed to lie fallow for several years to
replenish itself after which time it may again be planted to tung
trees. The idea apparently is current that the tree greatly ex-
hausts the soil and some time is required for it to recover. Evi-
dently no commercial fertilizer is used.
Trees on the Experiment Station grounds at Gainesville in
some cases have already exceeded the maximum height and trunk
diameter given above, and it would appear that conditions under
which these trees were grown were at least as favorable to the
22 Florida Agricultural Experiment Station
tree as are those in its native home. This is further borne out
by the fact that in 1931 one of the Gainesville trees produced a
crop of 164.8 pounds of hulled seed (roughly equivalent to 56.9
lbs. of oil) and the average production of 10 trees was 47.3
pounds of hulled seed during the same year.
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 in baskets slung on poles to
After the nuts are cleaned of trash they are roasted, then
ground by means of crude stone mills operated by manpower or
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 fash-
ioned 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, since much remains in the residue, and what oil is secured
usually is 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
important 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
The Tung-Oil Tree 23
other officials through whose districts the boats must pass. Only
to a limited extent are steamers used for transportation of oil
on the river.
Fig. 14.-Leaf of Aleurites fordi. Compare with Fig. 15. Both leaf
forms are of common occurrence on the same tree.
On arrival of the oil-laden junks at Hankow or other distrib-
uting 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
apparent purity. Transportation of the oil from Chinese ports
was formerly in barrels, for the most part American oak barrels,
24 Florida Agricultural Experiment Station
but in recent years considerable quantities have been shipped in
When prices for wood oil are high the temptation to adul-
terate 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 adulterated is rejected by the representatives of exporting
companies. Ling (15) reports that the principal adulterants
used are Stillingia, sesame seed, soybean, cotton seed and rape
Fig. 15.-Leaf of Aleurites fordi. Compare with Fig. 14.
While prejudice against modern inventions, adherence to old
customs, opposition to foreign progress and other factors mili-
tated against the use of modern methods in the development of
The Tung-Oil Tree 25
the tung oil industry in China in the past, there is evidence that
this situation is changing. In 1929 the Chinese National Govern-
ment started inspection of tung oil for shipment to foreign
destinations and has established a set of specifications on the
basis of the foreign requirements. Reports indicate that there
has been a great reduction in the adulteration of tung oil for
foreign export and a material improvement in the handling pro-
cedure. Research work has been started along several lines and
it may be expected that improvement will take place to meet
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, 1923 (21):
"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 re-
place 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 increas-
ing the prices of the finished products.
"Recently because the fighting has hampered the transporta-
tion the shipments that reached the river ports were mostly
INTRODUCTION OF THE TREE INTO THE UNITED STATES
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 be-
ing imported 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 lati-
tude 250 to 340 N. It is said not to bear when subjected to tem-
peratures as low as 200 F., although it will stand any degree of
26 Florida Agricultural Experiment Station
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 depending 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 ex-
traction of the oil. (Wilcox.)"
It seems that the first seeds 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
L. S. Wilcox at Hankow, China. These were received at the
Department'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
American consular representatives in China.
From time to time in succeeding years, the Department of
Agriculture 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 cooperators in the Carolinas, Georgia, Florida,
Mississippi, Louisiana and California, and, in 1913, David Fair-
child published a circular (6) 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.
PLANTINGS OF THE FLORIDA EXPERIMENT STATION
The first plantings of tung-oil trees on the grounds of the
Florida Experiment Station were made in 1912. Owing to the
fact that between 1912 and 1921 the supervision of the horticul-
tural 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
The Tung-Oil Tree 27
being that some trees in the original planting died and were re-
placed 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
Tree No. Date Planted Yield, 1916
6....................................... April 10, 1912 16 nutsl
7.................................. April 10, 1912 5 nutsl
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) 2
6, 8, and 9...... April 10, 1912,
and March 4, 1914 55 lbs. (5,550 nuts) 2
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 1922-1934, inclusive, are shown
in Table 2.
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.
In view of the stress now being laid on seed selection, attention
should be called to the variation in yields in these 10 trees. Over
a 13-year period the average yearly production varied from 4.7
pounds of hulled seed per tree to 67.3 pounds per tree or from
1.6 pounds of finished oil to 23.2 pounds of oil. The high yield
of a few trees brings the yearly average of all trees over a 13-
year period to 22.7 pounds of hulled seed (7.8 pounds of oil).
Similar variation may be expected in mixed plantings where no
stock selection has been practiced. It would seem that asexual
methods of propagation or, at least, careful seed selection in
planting would tend to make for trees of a more uniformly heavy
These trees (Fig. 2), spaced 10 feet apart in the row, grow
upon a gentle south slope on very sandy soil. They have re-
ceived very little cultivation and, so far as is known, no ferti-
lizers prior to 1923. Beginning with the spring of 1923 these
trees were given annually 10 pounds each of a commercial
1Apparently whole fruits.
2Hulled nuts or seed.
TABLE 2.-YIELDS OF 10 TUNG-OIL TREES ON HORTICULTURAL TEST GROUNDS, 9TH TO 21ST YEARS, INCLUSIVE.
1 1922 1 1923 ] 1924 | 1925 | 1926' I 1927 1 1928 I 1929 1 1930 | 1931 I 19321 I 1933 [ 1934 113-yr.totall 13-yr. av.
Lbs. lbs.Lbs. lbs. Lbs. Ibs. Lbs.lbs. Lbs.bs. Lbs.lbs. Lbsbs. Lbs.bs. Lbs. lbs. Lbs.bs. bs.bs. Lbs. lbs. Lbs. lbs. Lbs. lbs. Lbs. lbs. Seed oil
Tree Seed3 oil6 Seed| oil Seed oil Seedi oil Seed| oil Seed oil SeedSeedileed oil Seed oil Seed i oil Seed oil -Seed oil Seed oil Lbs.| lbs.
1 17.5 6.0 1.6 0.6 7.5 2.6 13.5 4.7 2.5 0.9 17.5 6.0 14.3 4.9 37.4 12.9 24.1 8.3 38.1 13.1 0.6 0.2 20.3 7.0 33.4 11.5 228.3 78.7 17.6 6.1
24 3.0 1.0 63.6 21.9 45.8 15.8 33.3 11.5 1.0 0.3 55.0 19.0 25.5 8.8 89.8 31.0 18.0 6.2 72.5 2.0 12.0 4.1 49.0 16.9 48.9 16.9 517.3 178.5 39.8 13.7
3 3.0 1.0 1.2 0.4 8.4 2.9 1.5 0.5 0.5 0.2 13.0 4.5 2.4 0.8 4.9 1.7 3.8 1.3 14.0 4.8 0.3 0.1 3.4 1.2 6.1 2.1 62.5 21.5 4.8 1.7
4 6.0 2.0 2.5 0.9 7.3 2.5 3.3 1.1 0.9 0.3 20.0 6.9 22.7 7.8 31.0 10.7 22.1 7.6 30.8 10.6 2.3 0.8 11.2 3.9 18.9 6.5 179.0 61.6 13.8 4.7 3.
5 12.5 4.3 5.8 2.0 3.3 1.1 3.4 1.2 0.3 0.1 5.0 1.7 4.5 1.6 4.4 1.5 1.5 0.5 7.6 2.6 0.9 0.3 4.5 1.6 6.9 2.4 60.6 20.9 4.7 1.6
65 13.5 4.7 38.5 13.3 39.5 13.6 52.0 17.9 0.4 0.1 50.0 17.3 11.3 3.9 66.9 23.0 14.1 4.9 64.1 22.1 13.3 4.6 61.0 21.0 18.5 6.4 443.1 152.8 34.1 11.8
7 8.5 2.9 10.5 3.6 11.8 4.1 19.5 6.7 0.4 0.1 15.0 5.2 5.3 1.8 35.8 12.4 6.9 2.4 19.2 6.6 4.4 1.5 5.1 1.8 12.3 4.2 154.7 53.3 11.9 4.1
8 14.0 4.8 40.1 13.8 37.3 12.9 16.0 5.5 12.4 4.3 48.0 16.6 23.3 8.0 39.3 13.6 22.8 7.9 38.6 13.3 0.8 0.3 16.9 5.8 16.5 5.7 326.0 112.5 25.1 8.7
9 5.52 1.9 18.0 6.2 89.0 30.7 75.0 25.9 10.1 3.5 90.0 31.0 84.8 29.3 141.7 48.9 33.2 11.5 164.8 56.9 5.8 2.0 58.3 20.1 98.3 33.9 874.6 301.8 67.3 23.2 '
10 5.5' 1.9 3.4 1.2 23. 8.1 0.8 0.3 6.3 2.2 14.0 4.8 9.1 3.1 5.0 1.7 7.0 2.4 23.4 8.1 .1 0.03 0.6 0.2 1.8 0.6 100.5 34.6 7.7 2.7
Avg. 8.9 3.1 18.5 6.4 27.3 9.4 21.8 7.5 3.5 1.2 32.8 11.3 20.3 7.0 45.6 15.7 15.4 5.3 47.3 16.3 4.1 1.4 23.0 7.9 26.2 9.0294.7 101.6 22.7 7.8
1Low yield of 1926 due to 27 F. on March 13, which froze flower buds; low yield in 1932 due to frost during bloom.
"2Yields of the two trees taken together and evenly divided for 1922.
Weight of air-dried hulled seeds.
'Fruit borne in clusters.
Some fruit borne in clusters some years.
"Pounds of oil was computed by considering that air-dried hulled seed contained 34.5% oil. This percentage is an approximation, and was obtained by
taking the Alachua Tung Oil Company's milling plant records of the amount of oil obtained from a mixture of all of the seed, for one year, from
the various Station plantings. This percentage will vary from year to year, depending upon growing conditions, also, it is not exactly accurate
for individual trees as the oil content of seed from individual trees varies.
The Tung-Oil Tree 29
fertilizer analyzing 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, superphosphate, and sulphate of potash. They now (1935)
average over 29 feet in height and 381/2 feet in average spread of
branches. Their trunk diameter, at a distance approximately
12 inches above the ground, varies from 71/2 inches to 231/2
inches, the average diameter being slightly over 14 inches. The
largest tree has a height of 341/2 feet, a spread of 52 feet, and a
trunk diameter of 231/ inches.
Table 3, 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. In addition to the data
given in the table the trees were subjected to a temperature of
160 F. in December of 1934, apparently without injury.
TABLE 3.-SHOWING THE NUMBER OF DAYS WITH MINIMUM TEMPERATURES
OF 320, 250, 200, AND 160 OR BELOW, RESPECTIVELY, AT GAINESVILLE,
BETWEEN 1912 AND 1934, INCLUSIVE.
Winter of 32 25, 20o 160
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
1929-30-..................................... 9 3 0 0
1930-31................................----- 11 0 0 0
1931-32......................... ....... 4 0 0 0
1932-33................................ 2 0 0 0
1933-34............... ....... ...-........ 5 0 0 0
The absolute minimum experienced by these trees was 15*F. on
January 3, 1928.
Comparative temperature data for various locations in Florida
are available in Bulletin 200 (10).
Additional plantings were made in 1922 and 1923 to ascertain
the effects of various fertilizer materials on growth and yield.
30 Florida Agricultural Experiment Station
Results thus far obtained are reviewed in the section on
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 early developments with the tung-oil tree
in Florida. Mr. Raynes was undoubtedly the first to attempt the
growth of the tree in the South. On 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 importa-
tion 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
appearing 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
The Tung-Oil Tree 31
of yearling trees to Tenant Ronalds, at Tallahassee, whose plant-
ings 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 Manu-
facturers' Association of the United States, Gillsboro, New Jer-
sey. From these seeds Mr. Nemzek produced 2.2 gallons of
oil-the first American-grown tung oil.
Fig. 16.-Oldest tung-oil tree in Florida, planted November 15, 1906, by
William H. Raynes near Tallahassee.
32 Florida Agricultural Experiment Station
On February 26 and again on March 22, 1914, freezing tem-
peratures 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 inter-
esting as showing the reaction of the tree to seasonal conditions
Blossoms First Ripe Last Ripe
Year Appeared F ruit Fell Fruit Fell
1909.....- ...-..... ? September 4 October 11
1910................... ..-. ? September 18 October 24
1911...........-.......I-... ? September 3 November 25
1912........................ April 3 September 10 October 19
1914.........................- March 29 | September 14 October 15
TABLE 4.-NUMBER OF DAYS WITH MINIMUM TEMPERATURE OF 320, 25,
200, AND 160 OR BELOW, RESPECTIVELY, AT TALLAHASSEE, BETWEEN
1904 AND 1924.
Winter of 320 25 20 16
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
By consulting the records of the Weather Bureau, the mini-
mum temperatures to which the Raynes tree has been subjected
at Tallahassee are readily determined. Table 4 shows the num-
ber of times, between 1904 and 1924, that minimum temperatures
of 32, 250, 200, and 16 or below, respectively, have occurred.
The Tung-Oil Tree 33
For example, during the winter of 1923-24 a temperature of 160
was observed once and a temperature of 200 or below was
recorded twice, the latter including, of course, the occasion upon
which the temperature went as low as 160.
Fig. 17.-Bearing grove of tung-oil trees on property of Dr. Tenant
Mr. Raynes died November 12, 1914. Shortly afterward his
home was burned and the tung-oil tree, being nearby, was severe-
ly 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 the late Tenant Ronalds, of Tallahassee, became in-
terested 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
34 Florida Agricultural Experiment Station
and young grove trees were killed. For several years thereafter
no care was given the planting except that it was pastured and
occasionally mowed. Beginning about 1925, and continuing for
a few years, a portion of the trees were fertilized but given no
cultivation. This 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 total
acreage at approximately 15,000 to 16,000. Large plantings now
exist in Alachua, Levy, Clay, Jefferson, Okaloosa, Lake, and Polk
counties with smaller plantings in practically all of the central
and north Florida counties. A considerable acreage is not now
being intensively cared for due to a variety of reasons and it is
difficult to estimate the acreage which is receiving good care.
The U. S. Agricultural Census now being taken will give accurate
data on the acreage.
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 tempera-
ture 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 satis-
factory growth until these are determined by a sufficient num-
ber of plantings made under varying conditions in southern
Florida. Plantings have been observed in the American tropics
and none of these have grown or produced satisfactorily. The
trees usually lost their leaves three to four times per year and
only an occasional fruit was set. This confirms former opinions
that the tree is not tropical in nature and definitely requires cool
winter temperatures for proper dormancy. These observations
are more or less confirmed by poor results obtained in plantings
in south Florida. In many plantings, however, it is difficult to
separate effects of soil conditions from the effects of climate.
From over 300 lots of trees or seeds sent from this Station for
testing purposes during the six years prior to 1930, quite varied
results have been reported. With these test lots it appears that
The Tung-Oil Tree 35
in many cases the trees were not given the attention they would
have received had they been grown in a commercial way, but
rather were planted and allowed to shift for themselves. As
would be expected, contrary reports as to results have been re-
ceived from the same counties, some from the same vicinities.
It is to be noted that some few reports from the northwestern
counties indicated some 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 plantings on wet, poorly-drained soils.
The tung-oil industry is still in the seedling stage, so to speak,
since in the main only seedling trees are being planted. Most
horticultural tree crops, as we know them, passed through this
stage during the earlier years of their existence but almost with-
out exception have changed to asexual propagation (budding,
grafting, etc.) In some sections of the world seedling trees still
form a basis for fruit or nut production but in such areas labor
and land are so relatively cheap as to overcome the irregularity
in production. In Europe and North America the extensive pro-
duction of fruits and nuts is based on the asexual propagation of
superior varieties. The result aimed at is the uniformly heavy
production of superior quality fruits. Seedlings normally show
tremendous variation in all characteristics unless a great deal
of breeding work has been done to produce so-called "pure lines."
In annual crops, such as vegetables and field crops, it is possible
to establish such uniform lines in a few years and we have our
varieties of beans, peas, wheat and corn which "come true" from
seed. Such a procedure is very difficult in a tree crop which
takes five to 10 years to come into bearing, so that it would take
from 25 to 50 years to accomplish in a tree crop what could be
accomplished in wheat in five years. Lacking the time for the
breeding of pure line varieties of trees that would come true
from seed, recourse is had to budding or grafting (asexual
propagation), since buds of a tree will reproduce the tree from
which the buds were taken.
Studies were undertaken at the Experiment Station with the
intent to establish certain definitely superior strains and to en-
courage the planting of these rather than the planting of mixed
seed. A study of variation in tung oil was reported on in
Bulletin 247 (11). In Table 2 will be found a record of the
production of the original 10 trees at the Experiment Station and
36 Florida Agricultural Experiment Station
it will be noted that, over a period of 13 years, the average an-
nual production per tree varied from 4.7 to 67.3 pounds of hulled
seed. While a portion of the trees have yielded well, several of
the trees may be considered as almost non-producers. That the
bearing ability of the various trees is quite a constant factor will
be found if the data are examined. Omitting 1922 because the
seeds of all the trees were not accurately separated and 1926 be-
cause of the almost total crop failure, it will be found that in 10
out of 11 years, Trees 2 and 9 are found in the three trees show-
ing the highest production each year and that Tree 6 was in this
group in 8 out of 11 years. Conversely, taking note of the three
trees producing the smallest crop in each year, Tree 3 will be
found in this group in 10 years, Tree 5 in 8 years and Tree 10 in
6 of the 11 years. It will be noted that none of the trees men-
tioned above appears in both groups at any time during the 11
Other characteristics besides yield are likewise found to vary
widely; in Figs. 5, 6 and 7 there is shown the variation in the
gross characters of the fruits coming from the original 10 trees,
Figs. 5 and 6 showing the ordinary variation and Fig. 7 the ex-
treme variation. In Table 5 will be found analyses of the fruits
of the original 10 trees and several of their progeny. It will be
noted that the variation in size of fruit and seed is very large,
whereas the variation in percentage of kernel and percentage of
oil is much less. A full report on the above will be found in
Bull. 247 of this Station.
The seed from these trees was widely distributed during the
early days of the tung oil industry and has formed the basis of
many plantings which have, in turn, furnished seed for a great
many other plantings so that, directly or indirectly, these trees
have formed the basis for the planting stock of a considerable
acreage. Later only seed from the best trees was sent out but
even these were subject to the possibility of having resulted from
cross-pollination from the adjoining low-yielding trees, so that it
may be said that the blood of the low-yielding trees is widely dis-
tributed in the commercial plantings and the same holds true of
plantings from other sources. In recent years much more care
has been exercised in the selection of seed, both by the Experi-
ment Station and by commercial seedsmen, so that the quality of
seed offered has greatly improved.
The first tree to become recognized as having unusual
possibilities was Tree No. 2 of the original 10. This tree has
been described by Mowry (11) under the varietal name Florida
TABLE 5.-FRUIT ANALYSES OF SEEDLING TUNG-OIL TREES, 1931 CROP (From Bul. 247).
Av. I Fruit Fruit Seed Kernel
I Weight Av. Av. Mature-Not dried | Air-dry Air-dry I
Fruit- Indv. No. No.
Tree ing Fruits Seed Seed Mean Mean I | Percent
SType* (Air-dry) I Per Per lb. Breadth Length Percent Percent Percent Percent Percent Oil
(oz.) Fruit (Air-dry) (cm.) *** (cm.) I Seed Hull Kernel Testa I Moisture I (Oven-dry)
1 | S 1 .67 4.38 167 4.82 .010 4.71 .010 62.6 37.4 59.6 j 40.4 5.64 I 60.92
2 | Cl .74 4.44 143 5.45 .014 5.01 .012 63.0 37.0 59.9 40.1 8.17 1 58.50
3 S | 1.44 4.11 115 5.92 .018 5.47 .014 55.0 45.0 65.3 34.7 6.20 60.89
4 | S F .44 4.15 227 3.48 .010 3.76 .009 63.6 36.4 | 58.9 41.1 5.07 62.08
5 | S .79 5.09 | 176 4.57 4 .014 4.31 .012 | 58.6 41.4 | 57.4 42.6 5.68 -59.71
6 S** .87 4.41 129 5.25 .014 5.06 .012 63.0 .0 0 62.6 37.4 5.80 | 59.09
7 S .86 4.48 133 5.36 .018 4.99 .012 63.1 | 36.9 1 63.3 36.7 1 5.75 59.34 -
8 9 S | 1.36 4.56 | 97 6.65 .015 5.96 .013 1 54.5 45.5 [ 65.1 34.9 F 6.00 60.65
9 S .78 4.54 171 5.51 .011 5.63 .011 60.7 39.3 F 56.0 | 44.0 | 7.11 53.97
10 S 1.34 F 4.36 85 6.29 .015 5.63 .013 60.9 39.1 | 66.0 F 34.0 10.72 60.54
A Cl .90 4.56 1 128 5.26 .014 4.92 .011 j 63.3 36.7 [ 61.5 F 38.5 9.05 60.14 9
B F S 1.05 4.28 130 5.92 .022 5.68 .017 50.2 49.8 62.5 37.5 6.36 55.51
C [ Cl .75 4.38 154 5.47 .016 5.16 .018 60.6 3 89.4 1 54.5 45.5 6.50 56.52
D | Cl .95 4.38 111 5.47 .022 4.96 .011 66.4 F 33.6 63.6 36.4 10.39 58.43
E S 1.11 4.54 108 | 6.31 .012 5.80 .010 | 61.0 39.0 62.8 37.2 6.76 58.97
F S 1.10 4.19 107 | 6.00 .014 5.75 .010 57.5 42.5 60.9 1 39.1 5.15 58.27
G Cl .77 4.39 147 F 5.52 .016 5.28 .014 62.2 I 37.8 59.9 F 40.1 6.63 60.15
H I Craig 1 2.08 7.28 F 105 8.03 .026 | 6.07 .017 53.5 | 46.5 1 61.1 1 38.9 | 4.83 56.63
Trees 1-10, inclusive, 18 years old; A-E, inclusive, 9 years; F, G, and H, 8 years.
*Cluster or single.
"**Has twice borne a small part of its fruit in clusters.
"***One centimeter equals .39 inches.
38 Florida Agricultural Experiment Station
but commonly goes under the terminology of the cluster type.
As has been previously mentioned, this terminology has arisen
from the fact that it usually bears more than one female flower
to the cluster and the fruits, as a consequence, are borne in clus-
ters (Fig. 18). This characteristic served to separate it sharply
from the other trees so that its progeny could be more easily
identified. Further studies showed that this characteristic was
transmitted by budding and to a considerable extent the seedlings
from this tree carried the same characteristic. It was assumed
that a tree that bore several fruits at a terminal would bear more
than a tree bearing only one fruit at a terminal, other things
being equal. The fruits of the Florida variety are of good size
and shape and studies of mixed groups of seedlings have shown
that the trees bearing fruit in clusters are usually superior as a
group when compared with all the single type trees as a group
(see records of fertilizer tests).
Fig. 18.-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.
The description of the Florida is given below but it should be
remembered that, while trees budded from the No. 2 tree will
fit the description given, not all seedlings of this tree will do so
though a considerable proportion of them will have the cluster
The Tung-Oil Tree 39
Technical Description.-Tree spreading, prolific; bearing its
fruit in clusters. Flower cymes usually with one or more lateral
pistillate blossoms in addition to an apical one. Fruit oblate-
spherical, somewhat flattened at apical end; base with short
neck and apex with a rather sharply pointed nipple; hull thin;
surface smooth, distinctly marked with deep green longitudinal
lines coincident with the inner segments or cell walls containing
the individual seeds; color usually green at maturity but a deep
red where exposed to full sun; size medium, the transverse diam-
eter from 4.6 cm. to .1 cm. with a mean of 5.45 .012 cm.
(standard deviation .304, and coefficient of variability 5.57 per-
cent), the longitudinal diameter, including neck, from 4.3 to 5.6
cm. with a mean of 5.01 .012 cm. (standard deviation .255, and
coefficient of variability 5.08 percent) ; average weight of air-
dried fruits .74 ounces; seeds 4 or 5 to each fruit, average 4.44
per fruit and 143 (air-dry) per pound; whole fruits (air-dry)
63.0 percent seed and 37.0 percent hull; seed (air-dry) 59.9 per-
cent kernel and 40.1 percent testa; kernel (oven-dry) 58.50 per-
cent oil; seed (air-dry) 32.18 percent oil; and whole fruit (air-
dry) 20.27 percent oil.
In studying Table 2 above referred to it will be noted that
Tree No. 9 has outborne Tree No. 2. Several factors enter into
the situation and it is impossible to weigh these accurately. Tree
No. 9 is much less crowded than Tree No. 2 and has grown to be
the largest tree in the group and this may have much to do with
the differences in yield. There are citrus trees crowding Trees
1 to 7 but No. 9 has not had this competition. In the early mixed
plantings it has been impossible so far to distinguish accurately
the progeny of Tree 9, since it does not have an outstanding
characteristic such as the cluster fruiting habit. Tests are
under way in which both seedlings and buds of No. 9 are being
compared with those from No. 2 but, until these have borne for a
few years, it will be impossible to determine their relative value.
For the present it has been deemed inadvisable to attempt a
varietal description of this tree or the wide distribution of its
Although plantings have been made on a variety of soils, it
is not yet possible either to define the most suitable soil type or
to outline 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 various locations in the state. Soil
40 Florida Agricultural Experiment Station
samples have been taken and general observations of tree growth
made in many plantings. The soil samplings have been made at
varying depths that the soil profile may be known. Such sam-
ples of the various soil types have been tested in the laboratory
for their reaction (pH value1) 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
cannot 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 suit-
able from a climatic standpoint for the culture of the tree.
As with other tree crops, well-drained soils are most exten-
sively planted. The Norfolk is perhaps-the soil series on which
tung-oil trees are now most widely grown. Sands to sandy
loams are planted to tung-oil trees, the finer sands and loams as
a general rule being excellent for its growth. A system of cover-
cropping 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 solis which have been planted to tung-oil
trees include the Gainesville, Orangeburg, Tifton, Orlando, Her-
nando and Greenville series. The Gainesville differs from the
Norfolk in containing particles of phosphate and limestone and
is of a brown to a reddish-brown color. The Hernando series is
very similar to Gainesville with considerable lime materials and
underlying limestone. Groves on both Hernando and Gaines-
ville soils have frequently given considerable trouble due to
bronzing, which will be discussed later. 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. The Tifton soils occur scatteringly in the
area west of the Suwannee River and are distinguished by their
pebbly iron concretions which are brown in color. The Orlando
soils occur largely in Orange and other south-central counties and
are closely related to Norfolk soils but higher in organic matter.
SThe 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, num-
bers smaller than 7 represent an acid or sour condition, the degree of
acidity depending on the smallness of the number.
The Tung-Oil Tree 41
Plantings have been made also on flatwoods soils in the Blan-
ton, Bladen, Coxville, 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 sub-
soil of sand with clay, seems well adapted when adequately
drained; the Coxville soils with a reddish clay-mottled subsoil
are very similar and are usually a little better drained naturally.
The Portsmouth series, with its black to gray surface soil and
light sand to sandy clay subsoil, 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 through
the hardpan when it is nqt too impervious and when the drainage
is established below it.
The question of whether or not the tung-oil tree should be
planted on the naturally 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 prohibitive, 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 com-
mercial fertilizers, the culture of tung-oil trees on the well-
drained soil types may be more profitable when drainage costs
are considered. The question of soil type evidently will be
governed partially by local conditions, and by the economic
factor of the demand and the supply of the product-tung oil-
which will control the price of the commodity.
A trouble commonly known as "bronzing" but probably a
form of chlorosis has been of common occurrence in many of the
plantings. The first symptom of "bronzing" is a deformation of
the terminal leaves (Fig. 19). This is followed by the develop-
ment of a bronze color of the leaves. This usually develops in
the early summer and is followed by severe winter-killing of the
twigs and branches, so that the tree is severely reduced in size
42 Florida Agricultural Experiment Station
This trouble has been found on many of the soil types on
which tung trees have been planted but has been particularly
severe on some of the soils which had been badly depleted by
cropping before being planted to tung trees. In general, it
seems to have been most severe on the rolling, pebbly soils which
are high in phosphatic materials.
Fig. 19.-Malformation of terminal leaves, an early symptom of "bronz-
ing" in the tung-oil tree.
Zinc sulphate applications have been found to be a corrective
for this trouble in most cases. Applications of zinc sulphate to
tung-oil trees, particularly in groves that have been attacked by
bronzing, is indicated. A broadcast application of 1/4 pound per
tree immediately after the trees come into leaf in the spring
should be sufficient on average trees under eight or nine years
of age. If, in some areas of the grove, bronzing shows up in the
summer, this application may be supplemented by a second appli-
cation in June or July. This work is discussed in detail in
Bulletin 273 (12).
An excess of lime in the soil and a soil reaction above pH 7
are liable to cause a chlorotic condition as shown in Figs. 21 and
The Tung-Oil Tree 43
23. This trouble may be closely related to bronzing discussed
above, the symptoms being very much alike in many ways. Be-
sides being malformed, the leaves are yellow to bronze in color
and the growth of the seedlings is characterized by short inter-
nodes and a bunched formation of growth as shown very well in
Fig. 21. The yellow leaves are noted on the new growth at the
top of the plant.
Fig. 20.-Three-year-old tung tree severely affected with bronzing, after
having made a good initial growth.
In general, it Would be better to avoid planting soils high in
phosphatic materials or which have been badly depleted by
cropping rather than attempting to depend on applications of
zinc sulphate. Figure 22 represents a stunted plant removed
from an over-limed area (pH value 8.04) in a nursery and plant-
44 Florida Agricultural Experiment Station
Fig. 21.-Chlorosis of tung-oil Fig. 22.-Showing recovery of a
foliage due to an excess of lime in stunted tung-oil plant after removal
the soil. from an over-limed soil to a soil with
an acid reaction.
Fig. 23.-Chlorotic and mal-formed conditions
of leaves due to an excess of lime in the soil.
The Tung-Oil Tree 45
ed in the same soil which had not received 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. The overliming was due to the lime being
dumped on limited areas some 10 to 12 years before the nursery
Fig. 24.-Stunted growth of tung-oil trees in a small area of a nursery
due to liming, with consequent alkaline reaction of soil.
However, when healthy seedlings from outside the over-limed
area (which had a pH of approximately 6.35) were placed in soil
from the overlimed area the unhealthy conditions shown in Fig.
21 were obtained. A study within the nursery itself gave the
results obtained in Table 6.
TABLE 6.-THE OCCURRENCE OF CHLOROSIS AND BRONZING OF ALEURITES
FORDI AS INFLUENCED BY EXCESSIVE LIME APPLICATION IN
NURSERY STOCK, SEPTEMBER, 1928.
Application of Lime Condition of Soil Sample pH of
Seedling Tree (inches) Soil Sample
Small amounts of lime applied Good growth 0-9 6.10
10 to 12 years before planting of seedlings
of nursery. 9-21 6.10
Lime dumped on ground. Bronzed seed- 0-9 7.90
Limited area of excess lime. lings; some died
out. 9-21 7.87
Lime dumped on ground. Seedlings show- 0-9 8.21
Limited area of distinctly ex- ing character- -
cessive lime. istic bronzing. 9-21 7.62
46 Florida Agricultural Experiment Station
Without sufficient drainage the trees will not continue to show
a thrifty and satisfactory growth, irrespective of cultural atten-
tion given them. Surface drainage alone is not sufficient; the
water table must be considerably below the soil surface level.
Present plantings are composed almost wholly of seedling
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 7 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 and more oppor-
tunity is offered for the elimination of poor seedlings.
The seeds do not remain viable over an extended period and
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. Approximately 60 days are required for germi-
nation. 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 (see p. 55), barnyard ma-
nures, and varying forms of nitrogenous fertilizers all have been
used to advantage 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.
Due to the prevalence of "bronzing" on some soils and to the
fact that trees so affected may be rendered unfit for use as plant-
ing stock, it is advisable to make an application of zinc sulphate
to the nursery in the spring or early summer. This material
should be applied over the surface of the soil covering an area 8
to 12 inches in width on either side of the row at the rate of one
pound of 89% zinc sulphate per 100 feet of row.
In the development of the nursery every effort should be
made to produce strong, vigorous growing trees. To obtain this
The Tung-Oil Tree 47
end, the advisability of locating the nursery upon the best soil
available cannot be too strongly emphasized. Where possible
the nursery should be planted upon new land, as the danger of
nematode attack and bronzing is greatly reduced.
Detail of patch budding of tung-oil tree.
Fig. 25.--Detail of patch budding of tung-oil tree.
48 Florida Agricultural Experiment Station
As previously pointed out, seedling trees are likely to be very
irregular in performance and numerous growers are showing in-
terest in asexual methods of propagation (budding or grafting)
in order to obtain uniform trees. While the absolute value of
these methods has
not been established,
it is desirable that
as many growers as
to some extent along
this line. Patch and
ring budding seem
to be the most
feasible methods of
stock (Fig. 25).
stock from seeds
planted the previous
February is used,
the work being done
in August, Septem-
ber and the early
part of October. The
budwood used is
from the current
season's growth, and
should be carefully
selected from trees
which have the
characteristics it is
desired to perpetu-
ate. A fairly large
percentage of the
buds are "blind",
but even a cursory
Fig. 26.-Budded tung-oil tree. Budded in examination will
April on 2-year root; photographed the follow-
ing November, the height then being 7 feet 8 disclose most of
inches. Fall budding has been found preferable these so there need
to spring budding. be but little loss due
to this cause if care is used when selecting the buds. Buds after
insertion are firmly bound in place with waxed cloth, such as is
The Tung-Oil Tree 49
commonly used in citrus budding. After 10 days to two weeks
the bud and stock will have formed a union, at which time the
wrapping cloth is removed.
The nursery trees containing the dormant buds are allowed
to remain as they are until growth starts the following spring.
When danger of frost is over, the stock should be "lopped" by
cutting it about three-fourths through on the budded side, five
or six inches above the bud, and bending over the top. This
leaves a narrow strip of bark to support the nearly severed top
and forces the bud into active growth. After the bud has reached
a height of from five to six inches the stock should be cut off
cleanly just above the point of union of stock and bud. Neither
staking nor tying of the growing buds has been necessary.
The young buds should receive one or two applications of
fertilizer, the first in the spring and the second in early summer.
Complete commercial fertilizers (see p. 55), barnyard manures,
and varying forms of nitrogenous fertilizers all have been used
to advantage for this purpose. These buds will be ready for
transplanting to the field the following winter, but only those
that have made a strong, vigorous growth should be used. Suf-
ficient information has not yet been accumulated to make possible
an estimate of the "take" which may be expected from buds.
In some trials as high as 95% "take" has been obtained but in
other cases a majority of the buds have been lost, frequently
due, it is believed, to the stock having hardened up a little too
much. Poor quality budding tape also has been a factor.
Dormant grafting has given very unsatisfactory results.
Bark grafting on larger trees during the summer months can
be practiced with a fair degree of success but no satisfactory
method of top-working has been evolved.
Other methods of propagation, such as by cuttings, have not
been successful. At the present time seedlings still constitute
the main planting stock but trials of budded trees should be en-
couraged in view of what has happened in other industries.
For the benefit of those starting nurseries the following data
are given: Fully matured and dried fruits will run approxi-
mately 56% seed and 44% hull and will run about 340 to 450
fruits to the bushel, with an average of about 41/2 to 5 seed per
fruit or about 1,700 to 2,000 seeds per bushel. The number of
hulled seed per pound varies from 85 to 244. The weight of a
bushel of dried fruits is about 30 pounds.
50 Florida Agricultural Experiment Station
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 require-
ments; namely, suitable soils
and thorough drainage, as
above mentioned, plus ample
cultivation, and adequate
S TRANSPLANTING AND
In general, the same meth-
ods are used in transplanting
tung-oil trees from the nur-
sery to the grove as with
other fruit or nut trees.
In this connection, the
question of the distance to
plant naturally presents it-
"self. As there are no very
old groves of tung-oil trees
in the United States, the
answer to this question is
yet largely problematical. On
the strength of the size at-
S trained by the trees in China
some have recommended that
they be planted as close as
20 feet each way. However,
Fig. 27.-Healthy and vigorous root it sees that this is too close
system of a young tung-oil tree. it seems that this is too close
for Florida conditions where,
with good care, the trees apparently 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 of soils.
It would seem best, in the light of present information, to set
the trees 25 x 25, 25 x 30, or even 30 x 30 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 transplant-
ing alternate trees to other groves when they become crowded.
There is every reason to believe that trees several years of age
The Tung-Oil Tree 51
can be transplanted successfully, if as great care be observed, for
example, as in transplanting large citrus trees. Whether this
could be done cheaply enough to make it pay is problematical and
the history of other ventures of this type would indicate that
very little of such transplanting will be done. In general it may
be said that the planting distance that is to be desired finally
should be followed from the start. In some of the plantings that
are 15 x 30 feet the trees are interlacing badly in the row before
10 years of age and the indications are that the maximum pro-
duction from such groves is likely to be reached at a relatively
early age. Experience with other tree crops would indicate that,
while crowding encourages precocity, it usually reduces peak
For the information of those planting groves the following
figures are given concerning the approximate number of trees
per acre required for various (rectangular) spacings:
Spacing Trees per acre
15 x 15 193
20 x 20 108
25 x 25 70
30 x 30 48
15 x 30 96
In removing trees from the nursery they may be dug with a
spade, being careful to retain most of the taproot, or a mechan-
ical digger may be used. The digger is simply a large U-shaped
blade pulled by a tractor. This cuts the side roots and the tap-
root so that the trees may be easily pulled. From the time the
trees are dug until they are planted the root system should be
carefully protected from drying out. The trees are usually cut
off 6" to 12"-above the ground for planting.
In setting the trees it is of utmost importance that they be
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. The use of well-decayed compost in the
planting holes has been very successful in giving trees a good
start, particularly on light soils.
All malformed nursery stock or trees which have become
stunted from any cause will ordinarily fail to grow into vigorous
field trees irrespective of attentions given later. A rigorous
grading and discarding of all nursery stock below a high stan-
dard is of utmost importance as an initial step toward a thrifty
It is important that the trees be transplanted while dor-
mant-that is, before they begin to leaf out in the spring. The
52 Florida Agricultural Experiment Station
transplanting of trees in foliage has been followed by a slow and
unsatisfactory growth. In the vicinity of Gainesville, in a
normal season, transplanting should be completed before Feb-
If the land to be planted has been cleared of oaks there is a
possibility of mushroom root-rot causing damage. To reduce
the danger of infection in such cases the plant pathologist ad-
vises that all old roots be carefully removed from the soil in
which the tree is to be planted (16).
During its first years the young tree evidently requires
sufficient cultivation to keep out encroaching grass and weed
growth within a radius of a few feet of the trunk if 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 cultivation in close proximity to the trees must be shallow
if the root system is not to be more or less seriously disturbed.
In general the most common practice is to grow a cover-crop
such as Crotalaria spectabilis in the middles during the summer
months and to disk this into the soil or plow it under in the fall
before frost. While the tree rows in young plantings must be
kept cultivated during the summer to prevent smothering of the
trees, this is not necessary in older plantings, though in four to
six year old plantings it may be desirable to clear out the growth
under the trees once during the summer. The shallow rooting
habit makes it undesirable to cultivate vigorously under the
trees and even in working in the cover-crop in the fall care should
be taken not to injure the root system too much. As the trees
mature the shade from the heavy foliage so reduces weed and
grass growth as to render intensive cultivation under the trees
Mulching the trees with weeds, grass or tung nut hulls has
given excellent results. The use of tung nut hulls is especially
effective as it seems to reduce bronzing materially. The chief
disadvantage of mulching is the fire hazard thus incurred.
Pruning of older trees, other than the removal of dead,
broken, or interfering branches, seems to be of no advantage
and unnecessary. Due to the manner of fruiting, the fruit be-
ing borne only on twig terminals of the previous season's
growth, any pruning evidently tends to reduce the number of
fruiting twigs with a consequent reduction of yields.
The Tung-Oil Tree 53
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 feet or more 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
as good results as are obtained with most other trees. It has
been the experience that, instead, the topmost bud or two will
shoot out a vertical growth which extends considerably, some-
times several feet, above the original pinched-out terminal be-
fore 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 obviously 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 only
solution known at present lies in cutting back the stock severely
at the time of transplanting, as previously mentioned. This
maintains the balance between the top and roots, producing a
more uniformly vigorous growth than can be obtained otherwise
and encourages the development of low-headed trees which are
more resistant to wind damage and shade the ground more
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
1/4 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 having
been practiced in a large way, the commercial practicability of
this method has not been determined.
54 Florida Agricultural Experiment Station
Fig 28Mto ofidcn aea rnhn i h ugolte.B e
-. .i-. z.-."
I, ---- -
,~~~.3 .. ,
Fig. 28.--Method of inducing lateral branching in the tung-oil tree. By re-
moval of bark above bud (left), lower branches were caused to grow on tree on
The Tung-Oil Tree 55
Fertilizer tests, inaugurated in 1923 to ascertain the most
efficient fertilizers, indicate that lack of nitrogen is the limiting
factor in growth, and that a complete mixture containing nitro-
gen, 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 be-
havior of unfertilized (check) trees. All trees were mulched,
once (in 1925) with Japanese sugarcane 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.
The results of the two fertilizer tests carried on in the Experi-
ment Station groves are shown in Tables 7, 8 and 9. It will be
noted that the experiments reported in Table 7 were discontinued
in 1930 due to the fact that the trees receiving no nitrogen were
in such bad condition that they had to receive a complete ferti-
lizer in order to put them in a growing condition. These plots
are located on a very coarse, deep sand (Norfolk) that had been
cropped to field crops for several years prior to planting to tung
trees and cannot be considered as indicative of maximum results
obtainable. The plantings are of mixed seedlings including a
scattering of cluster type trees and, for convenience in compari-
sons, the yields of the cluster type trees have been calculated
separately from the yields of the single type trees. A general
superiority of the cluster type over the remainder of the trees is
indicated, though this does not mean that there are not superior
strains of the single type.
Other fertilizer tests are now being carried on but have not
reached the point where a detailed report is justified. So far
they indicate the desirability of using a complete fertilizer with
at least a proportion of natural organic materials in their com-
position. Among such organic materials, chicken manure has
proven particularly valuable. The whole problem is considerably
obscured, however, by the discovery of the value of zinc sulphate
in correcting bronzing. There is evidence to indicate that the
demonstrated value of chicken manure and tung nut hulls is due,
in part at least, to the zinc content of such materials. In view of
this, the value of the results of fertilizer tests is open to a review
and further experiments are being carried out to establish eco-
nomical fertilizer recommendations where zinc sulphate is used.
TABLE 7.-YIELDS AND MEASUREMENTS OF TUNG TREES IN FERTILIZER TEST PLOTS.
1927 I I 1928 I 1929 11929 Avg.Tree Meas'rem's
Average Tree Yield I Average Tree Yield | Average Tree Yield 3-yr. Avg. Tree Yield I I
Pounds Single I Cluster 'Pounds Single Cluster Pounds Single Cluster Single Cluster Area of
Fertilizer Material Fert. Type Type Fert. Type | Type Fert. Type Type Type Type Trunk
applied Lbs.[ lbs. ILbs. lbs. applied applied Ls Cross c
per 2 per Lbs. lbs. Lbs. lbs. per Lbs. Lbs. lb. Lbs. lbs. Lbs. lbs Height Spread Section n
tree SeedI oil ISeed oil tree e Seed oil Seed oil tree Seed oil eed oil Seed oil Seed oil feet feet Sq.in.
Planted 1922-15 trees to plot.
Nitrate of Soda........ 8/4 7.2 2.5 5.8 2.0 1 0 0 1.5 0.5 1 5.4 1.9 6.0 2.1 4.2 1.5 4.4 1.5 9.4 13.2 18.9
Steamed bone meal 2 2.3 0.8 4.6 1.6 3 1.6 0.6 1.9 0.7 3 5.7 2.0 4.4 1.5 3.2 1.1 3.6 1.2 8.9 13.7 17.6
4-8-4. SA, 2%; DB,
2%; SP; MP ....... 3 2.5 0.9 5.6 1.9 4 2.0 0.7 0.8 0.3 4 3.8 1.3 4.6 1.6 2.8 1.0 3.7 1.8 9.3 13.4 18.8
Superphosphate.......... 1% 1.4 0.5 2.1 0.7 2 1.5 0.5 1.6 0.6 2 4.2 1.4 4.6 1.6 2.4 0.8 2.8 1.0 8.2 11.4 12.9 C
Muriate of Potash.... 1.1 0.4 2.9 1.0 1/3 0.8 0.3 2.1 0.7 1/3 1.4 0.5 5.2 1.8 1.1 0.4 3.4 1.2 9.4 13.4 16.6 I
Superphosphate and 1% 2 2
Muriate of Potash 0.6 0.2 4.9 1.7 1/3 1.6 0.6 2.4 0.8 1/3 2.2 0.8 6.3 2.2 1.5 0.5 4.5 1.6 9.8 14.1 16.9 m
Manure................. 18 2.1 0.7 6.1 2.1 20 4.5 1.6 2.6 0.9 20 5.1 1.8 8.6 3.0 3.9 1.4 5.8 2.0 10.2 14.4 20.5 3
Check (No fertilizer) 0 0.3 0.1 3.0 1.0 0 2.0 0.7 1.4 0.5 0 2.3 0.8 3.7 1.3 1.5 0.5 2.7 0.9 8.3 12.4 12.7
"All seed weights of air-dried hulled seeds. c.
"2Pounds of oil were computed by considering that air-dried hulled seed contained 34.5% oil. This percentage is an approximation and was obtained
by taking the Alachua Tung Oil Company's Milling Plant records of the amount of oil obtained from a mixture of all of the seed, for one year. CQ
from the various Station plantings. This percentage will vary from year to year depending upon growing conditions, also, it may not be exactly
accurate for any one plot due to the variation in oil content of the seed from individual trees. s.
'SA-Sulphate of ammonia; DB-dried blood; SP-superphosphate; MP-muriate of potash. .
The rows in the lower part of this block had gotten into such bad condition by 1930 that the fertilizer experiment as outlined above was discontinued.
TABLE 8.-YIELDS OF TUNG TREES IN FERTILIZER TEST PLOTS.
S1927 | 1928 1 1929 | 1930
Average Tree Yield Average Tree Yield Average Tree Yield AAverage Tree Yield
Amt. i Amt. I Amt. 1 Amt.
Fert. Single Cluster Fert. Single Cluster Fert. Single Cluster IFert Single Cluster
Plot per Type Type per Type Type per Type Type per Type Type
Tree Lbs.2 lbs. I Lbs. I lbs. Tree Lbs. I lbs. Lbs. I lbs. Tree Lbs. I lbs. Lbs. bs. Tree Lbs. Ibs. Lbs. bs.
I LIs. lbs.
(lbs.) Seed oil (bSeed oieed oil Seed oil (Ibs.) Seed oil Seed oil (lbs.) Seed oil Seed oil
Planted 1923-12 trees to plot, except Plot 4, which has 6 trees.
1 8 3.4 1.2 5.2 1.8 4 3.6 1.2 3.6 1.2 4 8.8 3.0 7.2 2.5 4 0.6 0.2 0.6 0.2
2 0 1.8 0.6 2.4 0.8 0 3.1 1.1 3.5 1.2 0 5.4 1.9 5.2 1.8 5 0.5 0.2 0.7 0.2
3 3 3.0 1.0 4.8 1.7 4 4.0 1.4 4.6 1.6 4 8.9 3.1 7.6 2.6 5 0.4 0.1 0.9 0.3
4 0 0.9 0.3 3.2 1.1 0 0.3 0.1 3.4 1.2 0 1.4 0.5 8.1 2.8 0 0.05; 0.02 0.6 0.2
5 3 4.5 1.6 6.7 2.3 4 4.8 1.7 7.3 2.5 4 10.8 3.7 15.5 5.3 5 0.7 0.2 0.5 0.2
6 20 1.1 0.4 4.1 1.4 20 1.5 0.5 3.9 1.3 20 5.8 2.0 6.4 2.2 20 1.2 0.4 0.3 0.1
7 3 3.3 1.1 5.0 1.7 4 4.4 1.5 6.1 2.1 4 8.3 2.9 6.9 2.4 5 0.4 0.1 0.7 0.2
8 5 1.7 0.6 4.9 1.7 5 2.3 0.8 4.3 1.5 5 5.1 1.8 9.3 3.2 6 0.2 0.1 0.2 0.1
1931 19321 1 1933
Average Tree Yield Average Tree Yield Average Tree Yield 7-year avg. Tree Yield
Amt. Amt. Amt
Fert. Single Cluster Fert Single Cluster Fert. Single Cluster Single Cluster
Plot per Type Type per' Type Type per Type Type Type Type 3
Tree Lbs. I lbs. I Lbs. lbs. Tree Lbs. lbs. Lbs. lbs. Tree Lbs. lbs. Lbs. lbs. Lbs. lbs. Lbs. I Ibs. i
[ (lbs.) Seed oil Seed oil (Ibs.) Seed oil Seed oil (Ibs.) Seed oil Seed oil Seed oil Seed oil S
1 5 19.1 6.5 19.3 6.6 5 0.3 0.1 0.9 0.3 6 7.5 2.6 5.7 2.0 6.2 2.1 6.1 2.1
2 5 20.0 6.9 20.4 7.0 5 0.3 0.1 1.1 0.4 6 3.9 1.3 6.8 2.3 5.0 1.7 5.7 2.0
3 5 20.1 6.9 32.7 11.3 5 1.0 0.3 2.1 0.7 6 5.6 1.9 13.2 4.6 6.1 2.1 9.4 3.3
4 0 5.0 1.7 18.5 6.4 0 0.05 0.02 0.9 0.3 0 0.4 0.1 7.9 2.7 1.2 0.4 6.1 2.1
5 5 22.2 7.7 39.7 13.7 5 0.2 0.1 1.4 0.5 6 6.0 2.1 17.5 6.0 7.0 2.4 12.7 4.4 a
6 20 26.7 9.2 22.2 7.7 20 0.5 0.2 1.2 0.4 20 3.6 1.2 8.1 2.8 5.8 2.0 6.6 2.3
7 5 25.9 8.9 35.7 12.3 5 0.07 0.02 3.1 1.1 6 6.8 2.3 10.0 3.4 7.0 2.4 9.6 3.3
8 6 16.6 5.7 28.9 10.0 6 1.5 0.5 1.5 0.5 6 4.8 1.7 9.2 3.2 4.6 1.6 8.3 2.9
*The fertilizers used were as follows:
Plot 1 Steamed bonemeal and cottonseed meal, equal amounts.
2 5-8-4 mixture (same as No. 5) with addition of 4 pounds air-slaked lime four times during eleven years. No fertilizer applied until 1930.
Lime applied 1923, 1926, 1930, and 1934.
"3 5-8-4 mixture (same as No. 5) with one application of lime as above at planting.
"4 Check-No fertilizer.
"5 5-8-4 mixture of 2% nitrate of soda; 1% sulphate of ammonia; 2% cottonseed meal; 8% superphosophate; 4% muriate of potash.
"6 Stable manure.
"7 5-8-4 mixture of 3% nitrate of soda; 2% cottonseed meal; 8% superphosphate; 4% muriate of potash.
"8 Steamed bonemeal.
Low yield of 1932 due to late frost occurring while the trees were in bloom.
2All seed weights of air-dried hulled seeds.
"Pounds of oil was computed by considering that air-dried hulled seed contained 34.5% oil. This percentage is an approximation, and was obtained C
by taking the Alachua Tung Oil Company's Milling Plant records of the amount of oil obtained from a mixture of all of the seed, for one year,
from the various Station plantings. This percentage will vary from year to year, depending upon growing conditions, also, it may not be exactly
accurate for any one plot due to the variation in oil content of the seed from individual trees.
TABLE 9.-MEASUREMENTS OF TUNG TREES IN FERTILIZER TEST PLOTS.
1929 1 1930 1 1931 ] 1932 | 1933
Avg. Tree Measure- Avg. Tree Measure- Avg. Tree Measure- Avg. Tree Measure- Avg. Tree Measure- 2.
ments ments ments ments ments
Amt.* | Area, I Amt. Area, Amt. Area, Amt. Area, Amt. Area,
I Fert. | Trunk Fert. Trunk Fert. Trunk Fert. | Trunk F ert. Trunk 4.
Plot | per I Cross- I per Cross- per Cross- [ per | Cross- I per | Cross- IQ
Tree Height SpreadSection Tree HeighSpread Section Tree Height SpreadHeighTree Height Spread Section] Tree Height Spread Sect:on
(lbs.) feet feet sq. in. (lbs.) feet feet sq. in. (lbs.) feet feet I sq. in. I (lbs.) feet feet sq. in. I (lbs.) feet feet sq. in.
Planted 1923-12 trees to plot, except Plot 4, which has 6 trees
1 4 10.5 14 19.3 4 13.1 15.2 25.7 5 12.8 17.7 31.4 5 13.7 19.0 32.6 6 14.4 20.7 44.0
2 0 9.9 11.9 13.1 5 12.2 13.7 20.1 5 12.3 16.0 24.7 5 12.5 17.4 28.9 6 12.8 19.1 34.5
3 4 10.7 13.1 20.0 5 12.8 15.7 27.2 5 13.3 17.8 32.6 5 13.8 19.6 37.1 6 14.4 21.1 44.5
4 0 8.1 10.8 11.0 0 10.3 12.2 16.9 0 10.6 15.5 19.5 0 11.2 16.7 22.9 0 11.4 17.9 27.6
5 4 11.2 15.1 20.4 5 12.6 17.1 26.9 5 12.6 18.2 30.3 5 12.8 19.0 34.8 6 14.2 19.4 41.2
6 20 9.7 12.5 13.4 20 10.9 13.7 19.5 20 12.0 16.6 23.4 20 12.4 16.7 25.8 20 12.5 19.1 31.1 H
7 4 10.9 15.6 18.6 5 13.7 16.1 24.5 5 14.8 19.2 30.3 5 14.7 19.7 34.8 6 15.5 20.5 40.7 3
8 5 11.1 14.6 15.9 6 12.0 16.1 20.9 6 12.8 18.0 26.6 6 13.2 18.7 30.7 6 14.6 20.6 36.0
*The fertilizers used were as follows:
Plot 1--Steamed bone meal and cottonsee] meal equal amounts.
2-5-8-4 mixture (same as No. 5) with addition of 4 pounds air-slaked lime four times during eleven years.
No fertilizer applied until 1930. Lime applied 1923, 1926, 1930 and 1934.
-- 5-8-4 mixture (same as No. 5) with one application of lime as above at planting.
5- 5-8-4 mixture of 2% nitrate of soda; 1% sulphate of ammonia; 2% cottonseed meal; 8% superphosphate; 4%c/1 muriate of potash.
"7-5-8-4 mixture of 3% nitrate of soda; 2'z; cottonseed meal; 8% superphosphate; 4% muriate of potash.
The Tung-Oil Tree 59
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.
The results of the fertilizer tests, together with the poor
performance of unfertilized groves, would indicate the import-
ance of fertilizer applications. Bud differentiation occurs during
the summer, as shown by Abbott (1), and any season's crop
will be dependent in a large measure on the condition of thrift
in the tree during the period prior to fruiting. Large yields,
without sufficient available plant nutrients in the soil to main-
tain 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. It has been
reported that groves on certain soil types have failed to respond
reported that groves on certain soil types have failed to respond
60 Florida Agricultural Experiment Station
TABLE 10.-OIL AND MOISTURE CONTENT OF SEEDS FROM TREES UNDER
DIFFERENT FERTILIZER TREATMENTS.
Nos. 1-16 Nos. 1A-16A
No. Fertilizer Cluster Type Single Type
__Moisturel Oil 'Moisturel Oil
1 Sodium nitrate...................................... 6.8 31.2 ........
1A Sodium nitrate..................................... ........ ........ 6.9 33.4
2 Bone m eal................................................ 7.8 36.1 ...
2A Bone m eal............................... ............ ........ ........ 7.4 35.2
3 4-8-4 mixture of ammonium sulphate,
2%; blood, 2%; acid phosphate,
muriate of potash.................. ...... 7.2 34.1 .. ......
3A 4-8-4 mixture of ammonium sulphate,
2%; blood, 2%; acid phosphate,
muriate of potash............................. ....... ........ 7.6 32.4
4 Acid phosphate................................... 6.7 32.5 ........ ........
4A Acid phosphate......................... .. ..... ........ 7.4 35.1
5 Muriate of potash.......................... 7.4 35.3 ........
5A Muriate of potash.............................. ....... ........ 8.1 35.0
6 Acid phosphate and muriate of potash 8.1 36.9 ........
6A Acid phosphate and muriate of potash ........ ........ 7.4 31.1
7 Manure ..... ................... ....... ...... 7.7 32.5 ...
7A Manure ..................................... .. ........ ........ 7.2 35.2
8 Checks (no fertilizers)......................- 7.3 33.6 ...
8A Checks (no fertilizers) ..---............... ..... ........ 6.8 36.6
9 Cottonseed meal and bone meal........ 7.1 35.1 ...
9A Cottonseed meal and bone meal....... ....... ........ 7.3 32.1
10 Lime (slaked) only.......................... 6.8 34.0 ........ ..
10A Lime (slaked) only........................ ..... ........ 6.8 36.9
11 5-8-4 mixture of sodium nitrate, am-
monium sulphate, acid phosphate
and muriate of potash, plus lime 6.6 31.8 ........ ........
11A 5-8-4 mixture of sodium nitrate, am-
monium sulphate, acid phosphate
and muriate of potash, plus lime ........ ........ 6.8 34.5
12 Check ........................... .................- 8.7 33.1 ...
12A Check ........................................ ..... ...... ........ 7.7 30.6
13 Same as No. 11 without lime.............. 7.2 35.3 ........
13A Same as No. 11A without lime.................. ........ 7.3 33.8
14 M anure ............ .......... ........ ........ 7.4 32.7 ........ ........
14A Manure ...................... .... ........ ........ 7.2 36.1
15 5-8-4 mixture of cottonseed meal,
sodium nitrate, acid phosphate and
muriate of potash........................... 8.1 32.9 ........
15A 5-8-4 mixture of cottonseed meal,
sodium nitrate, acid phosphate and
muriate of potash.............................. ........ ....... 7.8 35.4
16 Bone meal only............... ............... 7.6 32.9 .. ..
16A Bone meal only...................................... ....... ........ 7.6 35.1
to applications of fertilizers. Such groves have not grown vigor-
ously without fertilizer but rather have remained in poor con-
dition in spite of fertilizing. The evidence would seem to indicate
that such groves are unable physiologically to utilize fertilizer
due to poor soil conditions or for other reasons. In a number of
cases the trouble was due to bronzing, and the application of
zinc sulphate along with fertilizers has brought the grove into
The Tung-Oil Tree 61
good condition. A few groves, however, are not responding
satisfactorily as a whole to the zinc sulphate applications and
further experiments are indicated to determine the reason for
Owing to losses by leaching in sandy soils it seems advisable
that annual amounts of fertilizers be split into two applications;
the first being applied in early spring about the time of the
starting of growth and the second some time in June.
Samples of seed of the 1927 crop were taken from the various
fertilizer plots, as given in Tables 7 and 8, for the purpose of
determining any differences in oil content under different fer-
tilizer 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 10,
which gives these analyses, it will be noted that for the season
in question there is no apparent definite correlation between any
given fertilizer and percentage of oil in the seed. Other experi-
ments have shown, however, that badly starved trees may pro-
duce seeds with a low oil percentage, largely due to poor filling
of the kernels, and reports from China indicate a reduction in
oil content due to soil depletion.
Any leguminous cover crop grown between the rows of trees
is beneficial in that it increases both the nitrogen and the organic
matter content of the soil, most Florida soils being more or less
deficient in both. Because of their rank growth, adaptability
to various soils, and relatively small cost of seeding, the crota-
larias, both C. spectabilis and C. striata, apparently are giving
most satisfaction. The former species is well adapted to north-
ern sections of the state. After one planting it has been possible
to obtain volunteer crops in most succeeding years without fur-
ther seeding. With the younger trees the cover crop is confined
to the middles, a strip 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 nema-
tode attack should not be planted.
As far as picking the crop is concerned, the tung-oil fruit
may well be designated a "lazy man's crop". The fruits, ripen-
ing in October and November, fall from the trees as they mature.
62 Florida Agricultural Experiment Station
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 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.
EXPRESSING THE OIL
A plant for the expressing of oil from the seeds was erected,
equipped, and put in operation by L. P. Moore near Gainesville
in 1928, thus initiating the commercial production of tung oil
in America (Fig. 30).
Fig. 30.-Interior view of tung oil expressing plant located near Gaines-
ville. (Courtesy Alachua Tung Oil Co.)
In equipping the above plant the designing or manufacture
of new types of machinery for hulling and crushing was not
required, as it was found possible to adapt hullers and crushers
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 (testa), these waste products being
.removed and separated from the seed kernels by suction. The
The Tung-Oil Tree 63
seeds, by means of conveyors, are then passed through a grinder
and 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.
As now operated, the commercial production of oil amounts
to approximately 12 to 18 percent of the weight of the dry un-
hulled fruits, the fruits being air dried to approximately 12 to
15 percent of moisture before pressing. The pomace contains
approximately 4.5 to 5 percent of oil as it comes'from the expeller.
This seems to be close to the maximum recovery obotainable with
this type of equipment, though the residue of oil in the pomace
could probably be recovered by means of a solvent extraction
process. Some new improvements in the expelling equipment
may reduce the amount of oil in the pomace but this type of
equipment cannot be expected to recover all of the oil.
Considerable study is being given to making improvements
in milling procedures. Effort is being made to develop hullers
that can be used at the grove so that only the hulled seeds need
be transported to the mill and the hulls can be retained for mulch-
ing purposes. This will materially simplify the work at the
mill. A good deal of research is also being devoted by private
interests to the development of a solvent process similar to that
used in extracting soybean oil.
The principal product of the tung-oil tree is the oil, which is
expressed from the seed. Oil of fair quality is light golden or
light amber in color and, when free from impurities and of good
quality, is nearly transparent.
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
States, are given below:
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 25C-..................... --1.520 1.515
Iodine number (Wijs) -.................... ..--- - ... 163.0
A. S. T. M. heating test, minutes........ 12.0 ....
64 Florida Agricultural Experiment Station
A comparison of Florida tung oil with the above standards
demonstrates the high quality of the Florida product. The fol-
lowing analyses were made by Dr. H. A. Gardner (7):
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. 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, 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 industry. At
no time has a sample of oil been found to give abnormal prop-
The by-products, remaining after oil extraction, consist of
the hulls and pomace. Analyses, made by the Station's Depart-
ment 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 6 percent moisture, 5.9 percent nitrogen,
1.97 percent phosphoric acid, and 1.41 percent potash. 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 pomace
as fertilizer has not been determined because of the small quan-
tities yet available. This reaction, however, is assumed to be
satisfactory. The pomace, like the seeds, is poisonous; thus, it
cannot be used in stock feeds.
The Tung-Oil Tree 65
Imports of tung oil into the United States in 1933 amounted
to 118,760,000 pounds.
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.
A. fordi is the only species 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
The tree is now being grown on several soil types, it appar-
ently thriving best on soils having an acid reaction.
Excesses of lime and phosphate in the soil have proven
detrimental to tree growth. The use of zinc sulphate to prevent
bronzing is recommended.
Thorough drainage of soils is necessary.
The growing of summer leguminous cover crops in the tree
middles is highly desirable.
Complete fertilizers containing ammonia, phosphoric acid,
and potash and having an analysis of about 5-8-4, have shown
the best results in yield and tree growth. Manures also are
An apparent varietal difference, having to do with the number
of fruits borne on twig terminals, has led to the tentative desig-
nation of "single" and "cluster" types or varieties and a cluster
variety has been described under the name Florida.
Average yields on Station plots over a seven-year period
have been higher from the "cluster" trees. The highest indi-
vidual yield has been from a "single" tree.
Ten 21-year old trees in Station plantings have yielded in 13
years (ninth to twenty-first inclusive) an average of 22.7 pounds
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.
66 Florida Agricultural Experiment Station
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
One hundred pounds of fully matured and thoroughly dried
fruits consist of about 56 pounds of seed and 44 pounds of hulls.
A bushel of air-dried whole fruits weighs approximately 3034
pounds; the same quantity of air-dried hulled seeds weighs ap-
proximately 42 pounds.
The percentage, by weight, of the oil in the seeds varies from
28 to 40 percent, the average being about 331/3 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.
The writers are indebted to the late Dr. K. F. Kellerman,
Dr. David Fairchild, and R. A. Young, of the Bureau of Plant
Industry, United States Department of Agriculture, for infor-
mation generously supplied from the files of that department,
particularly as related to the introduction and distribution 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 infor-
mation; to B. F. Williamson, of Gainesville, for notes on the tung-
oil tree; to Ed L. Ayres for various notes, references, and pho-
tographs; and to the Alachua Tung Oil Corporation for infor-
mation relative to their tung oil expressing plant at Gainesville.
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