Title Page
 Table of Contents

Group Title: Bulletin - University of Florida Agricultural Experiment Station ; no. 171
Title: Preliminary report on experiments with the tung-oil tree in Florida
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00027078/00001
 Material Information
Title: Preliminary report on experiments with the tung-oil tree in Florida
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: p. 189-234 : ill. ; 23 cm.
Language: English
Creator: Newell, Wilmon, 1878-1943
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1924
Subject: Tung tree -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references.
Statement of Responsibility: by Wilmon Newell.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00027078
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000922820
oclc - 18171537
notis - AEN3329

Table of Contents
    Title Page
        Page 1
        Page 2
    Table of Contents
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
Full Text

Bulletin 171 May, 1924

Agricultural Experiment Station






FIG. 77.-Blossoming twig of a tung-oil tree.

Bulletins will be sent free upon application to the .Experiment Station,

'M olt-l

P. K. YONGE, Chairman, Pensacola
W. L. WEAVER, Perry
J. C. COOPER, JR., Jacksonville
A. H. BLENDING, Leesburg
J. T. DIAMOND, Secretary, Tallahassee
J. G. KELLUM, Auditor, Tallahassee
WILMON NEWELL, D. Sc., Director
JOHN M. SCOTT, B. S., Vice Director and Animal Industrialist
J. R. WATSON, A. M., Entomologist
R. W. RUPRECHT, Ph. D., Chemist
O. F. BURGER, D. Sc., Plant Pathologist
G. H. BLACKMON, B. S. A., Pecan Culturist
W. B. TISDALE, Ph. D., Associate Plant Pathologist, Tobacco Ex-
periment Station (Quincy)
G. F. WEBER, Ph. D., Associate Plant Pathologist
J. H. JEFFERIES, Superintendent Citrus Experiment Station
(Lake Alfred)
A. H. BEYER, M. S., Assistant Entomologist
C. E. BELL, B. S., Assistant Chemist
W. E. STOKES, M. S., Grass and Forage Crops Specialist
J. M. COLEMAN, B. S., Assistant Chemist
HAROLD MOWRY, Assistant Horticulturist
L. O. GRATZ, Ph. D., Assistant Plant Pathologist (Hastings)
ED L. AYERS, B. S., Agriculturist
A. S. RHOADS, Ph. D., Assistant Plant Pathologist
GEO. E. TEDDER, Foreman, Everglades Experiment Station (Belle
A. W. LELAND, Farm Foreman
JESSE REEVES, Foreman, Tobacco Experiment Station (Quincy)
J. G. KELLY, B. S. A., Lab. Asst. in Plant Pathology (Quincy)
ROBERT E. NOLEN, B. S. A., Lab. Asst. in Plant Pathology
MARY E. Roux, Mailing Clerk

K. H. GRAHAM, Auditor
RETTA MCQUARRIE, Assistant Auditor


INTRODUCTION .............. ..---------- 193
DESCRIPTION OF TREE .....---------...--... ----..------------------ ----193
RELATIONSHIPS .....-- ...----- --.---....--- .------ --------------------- 198
THE USES OF TUNG-OIL .......--------------- -----.-------------------. 201
THE WOOD-OIL INDUSTRY IN CHINA ..------------------- ---------------. 202
INTRODUCTION OF THE TREE INTO THE UNITED STATES............................. 205
OTHER FLORIDA PLANTINGS ..................------------------------ 212
FLORIDA GROVE PLANTINGS ................. .......... ............... 218
DISTRIBUTION OF TREES AND SEED ...........----- -------- ------------------------ 218
PROPAGATION ......----........-----------.------............... 219
TRANSPLANTING AND CULTIVATION ......----.....--------------------- -----.. 220
SOILS .... -----------------..........- ------------ --- 222
FERTILIZER ..............------------------------ -----...... 223
HARVESTING .-..- ----...------ ................------ ----. 223
PRODUCTS --........----...---... -----.--. ----.------------. 224
ADAPTABILITY TO CENTRAL FLORIDA .....----------------- --------------. 225
ENEMIES AND INSECT PESTS --.....------------..-------------------- 226
PROBABLE RETURNS --................---.---.---- ---------------- 230
CONDENSED INFORMATION ........----.---- ------- ------------------- 233
ACKNOWLEDGMENTS ...................-- ...---- ------ -- --... ......................--234


FIG. 78.-Tung-oil trees on the grounds of the University of Florida Experiment Station at Gainesville. Planted in
1912. and 1914.

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 Seed
and 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 and paint industries and its culture in America
is now attracting considerable attention.
From the nuts 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 re-
duces its liability to crack. It is said that strictly water-proof
varnish, as well as varnish which will not turn white under
long exposure to water, cannot be made without tung-oil as one
of its constituents. Its use in paints and varnishes is largely a
development of the last 15 or 20 years and its consumption
appears likely to steadily increase. According to David Fair-
child', the varnishes made with this oil and southern rosin, as
two of the constituents, are superior to those made with the
high-priced and rapidly disappearing gums, such as kauri, Ma-
nila, Zanzibar, etc.
The appearance of the tung-oil tree is not unlike 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,
often with three lobes. Leaves of both shapes are found upon
the same tree (figs. 79 and 80). The clusters are drooping and
the foliage dense. When twigs or leaf-stems are broken a milky
juice exudes, much as in the case of poinsettia and several other
plants belonging to the same family.
In habit the tree shows a marked tendency to branch low and
unless pruning is practiced the tree seems inclined to form a
straggling top or head rather than a straight, well-pronounced

'Circ. 108, Bureau of Plant Industry, U. S. D. A.

Florida Agricultural Experiment Station

central trunk. It is deciduous, shedding the leaves in the fall
and remaining dormant thru winter. The blossoms make their
appearance slightly in advance of the leaves. At Gainesville the
first blossoms appear at any time between March 1 and April
10, depending upon the season.

FIG. 79.-Leaf of Aleurites fordi. Compare with figure 80.
The flowers are borne in clusters, each blossom being white
and tinged or striped with pink (fig. 82). Each cluster is made
up of one or more female flowers surrounded by male flowers,
there being usually only one female flower to the cluster (fig.
81). In a count of 1,500 blooms, Harold Mowry' found an
'Assistant horticulturist, University of Florida Experiment Station.

Bulletin 171, The Tung-Oil Tree in Florida

average of 61 male blossoms to each female blossom. He also
noticed that in the case of the flowers of the extra productive
tree, known as "No. 2," in the horticultural grounds of the

L. -I -.

.-- ^


FIG. 80.-Leaf of Aleurites fordi. Compare with figure 79.. Both leaf forms
are of common occurrence on the same tree.

Florida Experiment Station, there were from two to five pistil-
late flowers to the cluster in numerous instances. This peculiar
flowering habit may account for the greater productivity of this
tree. It is also interesting to note that a single perfect flower-
one having both pistil and stamens -was found by Ed L.

FIG. 81.-Flower cluster of Aleurites fordi. Note that all blossoms shown in cluster are staminate ones except
the one in upper center.

Bulletin 171, The Tung-Oil Tree in Florida

Ayers' on a tree at Tallahassee. The clusters are not unlike
those of the catalpa. The tree in bloom is very attractive.
The fruit (figs. 84, 85 and 86) is from two to three inches

FIG. 82.-Flowers of the tung-oil tree, Aleurites fordi: pistillate (female)
flowers above; staminate (male) flowers below.
in diameter, dark olive green, 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. Each fruit consists of an outer portion or husk,

'Agriculturist, University of Florida Experiment Station.

Florida Agricultural Experiment Station

containing from three to seven firm brown seed'. The individual
seed in shape and color reminds one of an extremely large castor
bean, a near relative. The interior of the seed is white and the
meat decidedly oily. The nuts contain a poisonous substance and
must not be eaten. When the fruit matures it falls from the
tree and "harvesting" consists in simply gathering the fallen
fruit whenever convenient. The ripe fruit commences to fall in
October and all is off the trees by about the middle of December.
The following description of the genus Aleurites is given by
L. H. Bailey in "Manual of Cultivated 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 or floury.)"
His description of Aleurites fordi follows:
"A. fordi, Hemsl. China Wood Oil Tree. Tree to 25 feet high,
with glabrous branches: leaves ovate, 3-5 in. long, accuminate,
truncate or cordate at base, sometimes 3-lobed, loosely pubescent
beneath and becoming 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."
Aleurites montana, another member of this genus found in
Florida, has a five-lobed leaf and is, therefore, readily distin-
guished from it (fig. 88).


The tung-oil tree belong to the family Euphorbiaceae. Other
familiar plants belonging to this family are Phyllanthus, Croton,
Acalypha, castor bean (Palma christi), Euphorbias and Poin-
Of the genus Aleurites, five species appear to be described in
literature, as follows:

'R. A. Young, of the Bureau of Plant Industry, U. S. D. A., calls atten-
tion to the fact that, botanically, these seed are not true nuts. However,
they have been designated commonly as such and it is not likely that the
average grower will refer to them in any other way. In the present paper
the term "nuts" and "seed" are used interchangeably and refer to the
same part of the plant, namely, the true seed, rather than the whole fruit,
the latter consisting of both seed and husk.

FIG. 83.-Foliage and fruit of tung-oil tree, Aleurites fordi.

Florida Agricultural Experiment Station

Aleurites fordi, Hemsl., known as tung-oil tree, wood-oil tree
or (in China) "tung-shu" or "tung-yu shu," is a native of central
and western China and is the principal source of the tung-oil or
wood-oil of commerce. It is said to be much more hardy than A.
Aleurites montana (Lour) Wils., also known as tung-oil tree,
goes under the Chinese name of "mu-yu shu." It is the prevail-
ing species of southern China, altho this species and the fore-
going are said to be found together in certain of the Chinese
provinces. It requires a more sub-tropical climate than does
A. fordi." Young trees of montana, grown from seed imported
by the United States Department of Agriculture, are now grow-
ing at the Florida Experiment Station at Gainesville but are
not yet old enough to fruit. Records of the Office of Foreign
Seed and Plant Introduction (inventory No. 54703) show that
two-year-old seedlings of this species at Tallahassee were killed
by cold in 1917. At Gainesville in January, 1924, all one-year
seedlings of this species had their tops killed back from two to
six inches, while trees of A. fordi, of the same age, were not
Aleurites cordata, R. Br., known as the Japan wood-oil tree,
is cultivated in Japan and Formosa and is the source of a wood
oil differing in some important qualities from the oil produced
by the seeds of A. fordi.
Aleurites moluccana, Willd.. (synonym, Aleurites triloba),
known under the names of lumbang, kukui, candlenut, candle-
berry tree and varnish tree', is widely distributed in the tropics.
In some European countries oil from its seed is used in the

'Taylor, in his recent bulletin on "China Wood Oil" (Department of
Commerce, Miscellaneous Series-No. 125, Dec. 17, 1923, page 3) says
that Aleurites fordi "grows principally in south China, particularly in
Kwangsi Province" and that A. montana "is the hardier and more important
species and is found growing along the Yangtze River" (central
and western China). This apparently is an error, as all other available
accounts state fordi to be the principal source of oil, the more hardy of the
two species and the species most prevalent in central and western China.
Thus, Commerce Reports, No. 33, Feb. 9, 1921, states that montana is
largely confined to south China and fordi flourishes best in central and west
China. Similar information is found at various places in the inventory
records of the Office of Foreign Seed and Plant Introduction, United
States Department of Agriculture, notably under Nos. 25081, 36897 and
54703. Bailey's Encyclopedia of Horticulture also gives fordi as being the
hardier species.
'Not identical with the "Japanese varnish tree," Sterculia platanifolia
L., which is quite generally grown in Florida as a street tree; nor with
the Chinese tallow tree, Sapium sebiferum, which also grows in Florida.

Bulletin 171, The Tung-Oil Tree in Florida

manufacture of soap. A bearing tree of this species' is owned
by D. H. Cramer, of Lake Worth.
Aleurites trisperma Blanco (synonym, Aleurites saponaria),
known as banucalag, occurs in the Philippines.


In China, tung-oil has been used for many centuries and is
today extracted from the nuts by the same crude processes that
have been in use for many hundreds of years. Among the
Chinese it has many uses, these being for the most part such
uses as paints and water-proofing materials are put to in other
countries. The Chinese junk man uses no paint on his boat or
junk, but instead coats it with the cruder grades of wood-oil
(tung-oil). The residue remaining after the extraction of oil
from the nuts is burned to soot and is then mixed with wood-oil
to form a paste for caulking boats. Another caulking mixture is
made by mixing the oil with lime and bamboo shavings'.
The oil is used also as a natural varnish for houses, furniture
and other woodwork. It is used as a water-proofing material
for cloth shoes, clothing and paper-of which Chinese um-
brellas 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
manufacture of lamp black, while the burned oil and husks are
used in the making of Chinese ink, the latter familiar to all
artists and draughtsmen 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, and with aluminum
oxide it is made into aluminum tungate which is used as a fire-
proofing and water-proofing material. 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.
'Identified by W. E. Safford.
'U. S. Department of Commerce, Commerce Report No. 33, Feb. 9, 1921.

Florida Agricultural Experiment Station


With the exception of 1921, the annual imports of tung-oil
into the United States have increased each year. The following
statement of importations is taken from a recent publication'
of the Department of Commerce:

Calendar Pounds
Year Imported
1918............. .... ........ -------- 42,718,132
1919 ..............-..... ..-........ .-.... -..... --.. 53,852,595
1920 ... .............................. -- .------ ------ 67,962,150
1921 .. ....... ..... ... ......................... 27,248,887
1922..~..........-.......... ........ .. ... --------- ---- 79,089,292
According to the same authority, the importations during the
first nine months (January to September, inclusive) of 1923
amounted to 73,213,473 pounds, valued at $10,886,818.


Altho 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
Seed and Plant Introduction of the United States Department
of Agriculture and to a recent bulletin entitled "China Wood
Oil""1 issued by the Department of Commerce for information
as to the industry in China. The information given under this
head is taken mainly from these publications.
The Chinese have been familiar with tung-oil and have used
it for centuries. China is practically the only source of tung-oil,
or "wood-oil," as it is called. The latter name is not due to the
source from which it is secured but, rather to the fact that it is
extensively used as a wood preservative, in lieu of paint or 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 40F. (this doubtless
refers to A. fordi only), but that young trees with the sap flowing

'Taylor, William M.: "China Wood Oil." Miscellaneous Series-No. 125.
"Taylor, William M., loc. cit.

Bulletin 171, The Tung-Oil Tree in Florida

may be injured or killed by a sudden fall in temperature to 180
or 200F.""
It is said that the trees in China attain a height of from 10
to 30 feet and the trunks a diameter of from 6 to 10 inches, and
that they commence to bear when from 3 to 6 years old, yielding
from 30 to 40 pounds of seed to the tree annually.
As trees 12 years old, on the Experiment Station grounds
at Gainesville, have reached nearly the maximum height just
given and have in some instances attained a trunk diameter
greater than that given above, it would appear that conditions
in the vicinity of Gainesville are at least as favorable to the
tree as are those in its native home. This is further borne out
by the fact that in 1923 one of the Gainesville trees produced a
crop of 63 pounds of seed (husked nuts) and the average pro-
duction of 10 trees was 181/2 pounds.
In China the harvesting, shelling and grinding of the nuts,
as well as the extraction of the oil therefrom and its subsequent
handling, are all crude operations. The fruit is left on the
ground until the husk decays sufficiently to permit its being
broken up with comparative ease and the seed removed; in other
cases, the nuts are placed in piles and covered with straw where
they are allowed to ferment. The seed are then removed by
hand. The husked nuts are carried to small Chinese mills by
means of baskets slung on poles.
After the nuts are cleaned of trash they are roasted, then
ground by means of crude stone mills operated by manpower
or 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, as much remains in the residue and what oil is secured
is usually mixed with dirt and more or less extraneous matter.
After being strained it is placed in bamboo baskets lined with
many layers of water-proofed paper and provided with covers
made of the same material.
From the small mills the oil is purchased by agents and trans-
ported, in the baskets, by coolie labor to collection stations or
to river points where transportation to the coast begins. It is

"Taylor, William M., loc. cit.

Florida Agricultural Experiment Station

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
other officials thru whose districts the boats must pass. Only to
a limited extent are steamers used for transportation of oil on
the river.
On arrival of the oil-laden junks at Hankow or other dis-
tributing points, the baskets are unloaded by coolie labor and the
oil placed in tanks. Here further settling takes place and the oil
is separated into different grades, according to color and ap-
parent purity. Transportation of the oil from Chinese ports was
formerly in barrels, for the most part American oak barrels,
but in recent years considerable quantities have been shipped
in tank steamers.
When prices for wood-oil are high the temptation to 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. Tea oil, sesame oil, tallow and even pea-
nut oil are said to be among the adulterants used.
Prejudice against modern innovations, a strict adherance to
ancient customs, opposition to foreign progress, ignorance and
the unsettled conditions in China all operate effectively against
the use of modern or labor-saving methods in the growth of the
tung-oil trees, the processes of milling, efficient methods of
transportation and direct methods of selling, all of which are
considered as vital necessities in connection with the supply of
raw material for any great industry.
It is little wonder, therefore, that American paint and varnish
manufacturers should turn toward Florida as the place where
it may be possible to develop a permanent and dependable sup-
ply of the oil which has become indispensable in the manufac-

Bulletin 171, The Tung-Oil Tree in Florida


ture of many of the products now essential to the industries
and comforts of all civilized peoples.
A Chinese view on the tung-oil situation is well expressed in
the following paragraphs, taken from the North China Stan-
dard, published at Peking, November 14, 1923:"
"Unless political and commercial stability soon returns to
Szechwan, American varnish manufacturers may be compelled
to seek another source for their raw products and may even have
to change their processes in order to use other products.
"When research showed that the wood-oil of China could
replace the gums that were used for most of the varnish prod-
ucts, 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 in-
creasing the prices of the finished products.
"Recently because the fighting has hampered the transporta-
tion the shipments that reached the river ports were mostly
It seems that the first seed to produce trees in America were
imported from China in 1905. In that year the United States
Department of Agriculture received nuts from Consul-General
L. S. Wilcox at Hankow, China. These were received at the
Department's Plant Introduction Garden at Chico, California,
March 18, 1905, and were presumably 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. This interest was,
no doubt, responsible for the sending of planting stock to Amer-
ica for trial by the Department of Agriculture.
In Bulletin 97 of the Bureau of Plant Industry, published in
1907, the following notes on the tree appear:
"The fruit of this tree is the source of 'wood-oil' which is
being 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 thruout the Yangtze Valley in
latitude 25 to 34 N. It is said not to bear when subjected to
temperatures as low as 20F., altho it will stand any degree of
heat. The trees are raised from seed in a bed and transplanted
"Quoted from Chemical Trade Bulletin 8d, Department of Commerce,
January 11, 1924.

Florida Agricultural Experiment Station

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 extraction of the oil. Persons growing the wood oil tree
should be cautioned against allowing the oil to come.in contact
with the skin, as it is extremely poisonous. (Wilcox.)"
From time to time in
succeeding years, the De-
partment of Agriculture
received seed of the tung-
oil tree from China, rec-
ords of which appear in
the published Inventory
Lists of the Office of For-
eign Seed and Plant In-
Between 1905 and 1912,
the Department distribut-
ed tung-oil trees to va-
rious cooperators in the
Carolinas, Georgia, Flor-
ida, Mississippi, Louisi-
ana and California, and
in 1913, David Fairchild
published a circular" de-
scribing the tree, its uses
and its behavior at sev-
eral of the southern points
where it had been plant-
ed. In this publication
Dr. Fairchild expressed
the opinion that its cul-
ture would prove reason-
ably profitable, especially
in southern lo c ali t i e s
which do not experience
too low a winter tempera-
ture and where grown
upon cheap land.
FIG. 84.--Fruit of Aleurites fordi. Each
"Cire. 108, Bureau of Plant fruit contains from three to seven seed
Industry, U4 S. D. A. or "nuts."


Bulletin 171, The Tung-Oil Tree in Florida


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 hor-
ticultural grounds at the
Station changed hands
frequently, and due to
the cramped finances of

FIG. 86. Cross section of
fruit of Aleurites fordi,
showing three seed or
"nuts" within.

Tree No. D
6 Ap
7 Ap

FIG. 85.-Fruit of Aleurites fordi. Each
section contains a seed.

the Station, full and complete notes
on these trees were not kept. Cer-
tain definite records have been lo-
cated of plantings in this row in
1912 and 1914, the assumption being
that some trees in the original plant-
ing died and were replaced two years
The first record of yield is given
under date of November, 1916, and
refers to two trees as follows:

ate Planted
ril 10, 1912
ril 10, 1912

Yield, 1916
16 nuts"
5 nuts

The next record is that of November, 1918, and is as follows:

Tree No.
6, 8 and 9

Date Planted
March 4, 1924
April 10, 1912 and
March 4, 1914

Yield, 1918
40 lbs. (4,000 nuts)"
55% Ibs. (5,550 nuts)"

"Apparently whole fruits.
"Shelled nuts or seed.

Florida Agricultural Experiment Station

The 1919 record seems to be missing, but in 1920 the follow-
ing 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
Apparently no record was made of the yield in 1921, but in
1922 and 1923, the yields were as follows:
Tree No. Date Planted Yield, 1922 Yield, 1923
1 March 4, 1914 17% Ibs. 1 lb. 10 ozs.
2 March 4, 1914 3 lbs. 63 lbs. 8 ozs.
3 March 4, 1914 3 lbs. 1 lb. 3 ozs.
4 March 4, 1914 6 lbs. 2 lbs. 8 ozs.
5 March 4, 1914 12% lbs. 5 lbs. 12 ozs.
6 April 10, 1912 13 lbs. 38 lbs. 8 ozs.
7 April 10, 1912 82 lbs. 10 lbs. 8 ozs.
8 April 10, 1912 14 lbs. 40 Ibs. 2 ozs.
9 March 4, 1914 11 lbs." 18 lbs.
10 March 4, 1914 ............. 3 lbs. 7 ozs.
Total crop, 10 trees, 89 lbs. 185 lbs. 2 ozs.

These trees (fig. 78) grow upon a gentle south slope, on very
sandy soil, have received no cultivation in recent years and,
so far as known, have never received any fertilizer. They now
average about 21 feet in height, with average spread of branches
of 26 feet. Their trunks, at a distance of 12 inches above ground,
vary in diameter from 7 to 17 inches, the average diameter
being 8.4 inches.
Considerable variation in productivity is noted in the case
of these trees. Some are consistently shy bearers, while others
produce fair crops. The tree designated as No. 2, particularly,
has been a fairly heavy producer. However, its production was
low in 1922. Strangely enough, also, young trees grown from
the seed of this tree show a somewhat different habit of growth
from the seedlings of the remaining trees. Seedlings from No. 2,
even in the nursery row, show a distinct type of branching, so
much so that, familiar with it, one can go into a young grove
planting and pick out with certainty the seedlings of this tree.
These phenomena are interesting and point to two possibilities:
First, there are likely to be strains within the species which are
much more productive than others; second, at least some of the
characteristics of the parent tree seem to be transmitted to its
seedling progeny. Fortunately, it is possible to perpetuate by
the usual horticultural methods of budding and grafting any

"The 1922 production of 9 and 10 together.

Bulletin 171, The Tung-Oil Tree in Florida

particularly desirable strain. A number of investigators, in-
cluding Harold Mowry, assistant horticulturist, have successfully
budded tung-oil trees, using tung-oil seedlings as stock, but up to
the present time the budded trees have shown no indications of
greater vigor than have seedlings.

FIG. 87.-Seed of Aleurites fordi after removal from the fruit, i. e., after
being "husked." These are about the natural size.
The accompanying table, containing data taken from the
United States Weather Bureau records of the Gainesville station,
shows the minimum temperatures to which the bearing trees on
the Station grounds have been subjected.
Winter of | 32 25 20 I 16
1911-12 ................ 17 2 0 0
1912-13 ................ 3 0 0 0
1913-14 ................ 10 0 0 0,
1914-15 ................ 8 1 0 0
1915-16 ................ 18 1 0 0
1916-17 ................ 14 3 2 0
1917-18 ................ 21 11 2 0
1918-19 ............... 9 3 0 0
1919-20 ................ 18 1 0 0
1920-21 ...........- ... 1 0 0 0
1921-22 ................ 5 0 0 0
1922-23 ................ 6 1 0 0
1923-24 ................ 12 2 0 0
During the last five years, nursery trees have been grown on
the Station grounds in quantity from seed of the bearing trees
mentioned above. For the most part, the young trees have been
grown in old, sandy land which has been used for a number of
years for various purposes, and little or no fertilizer has been
used. Seed have also been planted at various seasons but the


210 Florida Agricultural Experiment Station

best results have been secured by planting the seed in February.
About 60 days are required for germination .in the field.. By
planting in February the majority of seedlings are, by the
following winter, from 10 to 16 inches high and large enough
for planting in the grove. When seed are planted in late spring
or in the summer, germination is slow and irregular and the
young seedlings are so tender the following autumn that they
are readily injured by the first frost. On the whole, trees 18
months old, grown from summer seedlings, have not been as

A, ,... i

FIG. 88.-Typical leaf of Aleurites montana, a species not as hardy as
Aleurites fordi.

Bulletin 171, The Tung-Oil Tree in Florida

desirable for planting as yearling trees grown from winter-
planted seed.
Some difficulty has been encountered with root-knot where
the .seed have been planted in land badly infested with the nem-
atode (see paragraph on Enemies and Insect Pests), making it
necessary to discard trees so infested when transplanting.
In April, 1922, a four-acre grove of seedlings was planted
on sandy land on the Experiment Station farm. These received
no fertilizer that year but during the following winter an experi-
ment was commenced involving the use of various fertilizer
combinations, the plan being to apply the same fertilizer to each
row thru successive years. Up to the present time no varying
effects from the different fertilizers can be observed. Additional
grove plantings were made on the Station farm in January,
1923, and still another one in December, 1923. All of these blocks
are being used in an extension of the fertilizer experiments,
as well as to note the effects of cutting back in different ways
when planting.
Nuts grown on the Station grounds, harvested in the fall of
1919 and kept until the following March, were analyzed by
Robert E. Hardee of the Station's Department of Chemistry, with
the following results:
Percentage Percentage Percentage
moisture oil ammonia
Whole seed" ............. 7.47 21.4 2.67
Hulls ........................ 14.39 0.99 0.60
Meats ......... ............ 3.58 32.59 3.82
Extracted meats
(pomace) ................ 0.05 ....... 5.66
From the foregoing it will be noted that the residue, or
pomace remaining after extraction of the oil, contains nearly 6
percent of ammonia, sufficient to have a distinct fertilizing
value. The pomace, like the nut, is poisonous, hence its only
value appears to be as a fertilizer. It cannot be used in stock
Mr. Hardee also found that the average weight of 100 shelled
nuts was seven-eighths of a pound, or 114 to the pound, ap-
proximately 5,000 to a stricken bushel. He also found that the
meat constituted 64.03 percent of the total weight of the fruit.
It should be borne in mind that these nuts were kept stored in

"Whole fruits.

Florida Agricultural Experiment Station

a dry place from fall until the following March and, having had
an opportunity to dry out, probably showed a lower moisture per-
centage than would nuts more recently harvested. As a matter
of fact, Henry A. Gardner, of the Institute of Paint and Varnish
Research, Washington, D. C., reported the following results from
analyzing tung-oil nuts grown on the grounds of the Florida
Experiment Station in 1920:
Percentage of shells ...............-.............-----...-...... ----------..... 55
Percentage of meat ..........--...... -........................-- -------------. 45
Percentage of oil in meat ..........--.....................---- ...........-------. 49
Mr. Mowry has found that fully matured and thoroly dried
fruit will run, by weight, approximately 56 percent of seed and
44 percent of husks.
The rather excellent showing made by the bearing trees on
the Experiment Station grounds, together with the Station's
demonstration of the relative ease with which the young trees
may be grown in the nursery, has attracted the attention of
horticulturists as well as of manufacturers who have occasion
to use tung-oil in their operations. This also has raised, quite
naturally, the question as to whether it is possible to produce
tung-oil profitably in this country. Conditions in China make
an assured and adequate supply of oil from that country more
or less uncertain. The imported oil is frequently inferior in
quality or is adulterated, and prices therefore are subject to
sudden changes. An American source of supply is much to be
desired and, if such can be developed, it will doubtless go far
toward stabilizing and insuring the future welfare of the paint
and varnish industries.

To the enthusiasm and experimental work of the late William
H. Raynes, a well-known horticulturist of Tallahassee, is due
much of the credit for what developments have already taken
place in connection with the tung-oil tree in Florida. Mr. Raynes
was undoubtedly the first to 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,
to which the author has been permitted to refer thru the kind-
ness of B. F. Williamson, of Gainesville.

Bulletin 171, The Tung-Oil Tree in Florida

In spite of the careful nursing of the five trees, all but one
died. On March 24, 1907, a severe gale nearly destroyed this one
and it had to be cut back to a height of three feet.
In 1908 the tree blossomed and that year produced three
fruits-just "three years from the planting of the seed nut at
Chico, Cal." This tree evidently came from the first importation
of nuts 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
distributed 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 thru 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 nuts and these he sent to Washington. He also records
that in November of that year his tree had a circumference of
24 inches at a point 12 inches from the ground and that the
spread of the branches was 23 feet. He also supplied a number
of yearling trees to Tenant Ronalds, at Tallahassee, whose 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 nuts. These he sent to L. P.
Nemzek, representing the Educational Bureau, Paint Manufac-
turers' Association of the United States, Gillsboro, New Jersey.
From these nuts Mr. Nemzek produced 2.2 gallons of oil-the
first tung-oil from American-grown nuts.
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 con-
sequence the production of nuts 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 readily 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 nuts of
each season's crop. This data, shown in the following table, are

Florida Agricultural Experiment Station

interesting as showing the reaction of the tree to seasonal con-
ditions at Tallahassee.



1909................ ?
1910..-........... ?
1911............... ?
1912................ April 3
1914................ March 29

First ripe
nut fell
September 4
September 18
September 3
September 10
September 14

Last ripe
nut fell
October 11
October 24
November 25
October 19
October 15

FIG. 89.-Oldest tung-oil tree in Florida, planted November 15, 1906, by
William H. Raynes near Tallahassee.


~r! -" ''~~-S~ i'";-"-. -.

Bulletin 171, The Tung-Oil Tree in Florida 215

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 5 shows the num-
ber of times, between 1904 and 1924, that minimum tempera-
tures of 320, 25', 20 and 16 or below, respectively, have
occurred. For example, during the winter of 1923-24 a tem-
perature of 16 was observed once and a temperature of 200
or below was observed twice, the latter including, of course,
the occasion upon which the temperature went as low as 16.
BETWEEN 1904 AND 1924
Winter of 32 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 .............i 12 1 0 0
1915-16" .............. 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 ............-..I 2 0 0 0
1921-22 ................I 8 0 0 0
1922-23 ............. 4 1 0 0
1923-24 ................ 12 4 2 1
Mr. Raynes died November 12, 1914. Shortly afterward his
home was burned and the tung-oil tree, being nearby, was
severely injured. The tree is now (1924) 27 feet high and the
trunk has a circumference of 52 inches at a distance of one foot
from the ground (fig. 89). In 1923 it produced about 150
pounds of whole fruits.

In 1913 Tenant Ronalds, of Tallahassee, became interested in
the tung-oil tree and planted four acres. This was to become
the first bearing tung-oil grove in Florida. In 1915 he increased
his plantings to 40 acres. The grove was well cared for until
the freeze of 1917, when young nursery stock and young grove
trees were killed. Since 1917 no care has been taken of the

"Data incomplete.

Florida Agricultural Experiment Station

grove except that a portion has been kept mowed and pastured.
Portions of it have burned over occasionally and ten acres have
been entirely removed. However, some of the trees are still in
good condition and bear fair crops, considering the lack of care
and fertilization (fig. 90).

FIG. 90.-Bearing grove of tung-oil trees on property of Dr. Tenant
Ronalds, Tallahassee.

The results of the work being done at the Florida experiment
Station with the tung-oil tree have been directly responsible for
the recent organization of a company for the production of
tung-oil in Florida upon a commercial scale. The stock in this
company is held principally by paint and varnish manufacturers
of the United States, about seventy in number. This company
has made, during the winter of 1923-24, an initial grove planting
of tung-oil trees, near Gainesville, of about 270 acres. Private
individuals and land owners also have shown an interest in the
tree and several small plantings of from one to ten acres have

Bulletin 171, The Tung-Oil Tree in Florida

been made recently. Most of these are in Alachua County. It is
estimated that there are about 500 acres in groves in Florida,
most of which are, however, plantings of the winter just passed.
From time to time for several years the Experiment Station
has distributed for testing young trees to individuals in various
parts of the state. Some also have been planted as street trees
by certain towns and villages.
The largest tung-oil tree yet located in Florida is growing
in the cemetery at Tallahassee (fig. 91). Measured by Ed L.

FIG. 91.-Largest tung-oil tree in Florida; growing in cemetery at Tal-



218 Florida Agricultural Experiment Station

Ayers in April, 1924, it was found to be 37 feet in height and to
have a trunk circumference of 44 inches. In 1923 it produced 300
pounds of whole fruits.


From all information available a somewhat careful count and
estimate has been made of the number of tung-oil trees at present
planted in Florida, other than those in nurseries. This estimate
is given below:



hua -..........- --.........-- ...---. 30 34,594
ford ....... ---...... .......... ........ .... 200
...-...--....----- .. ...- ....-- .... 106
im bia ..........................------ .. ... .. .. 212
al ............-- ...........-----...-....- ... 1 6
ambia ....- ... -- .. --- .. 58
lilton .-......- ----------..~........ ...---- .... 20
borough ...-............ ... .......... 37
person ........... .....- ..... .. ....... 4 25
n .......... .. .. --...... -.........- ... 3,231 ?
ion ........---. ----..---... --------... ...... .... 10
nge .......--.... ..... ..... ... ...-- .... 205
co ..... .. .. ..... ......................... .... 6
m Beach ----.......--- ... .. 14
llas ..........-.....--- .........-........ ... 4 0
. .... ......... ......... .... 10
nam --..~. ~~. ..-._ ........ -... -... ...- .... 356
Lucie ...... ..---- .....---- ..--- .....------- .... 40
inole -.......... ................-.... ... 2
annee .............--- .......- ........ -- .... 10
ton ---.~...... .- ----...~......- .... 4
Totals---...-.. .......-..-.. ----......... 3,307 35,878
Grand Total.....--..--....-...-- ..-.-------------------- .39,185


Prior to the winter of 1923-24 the Experiment Station dis-
tributed to various experimenters in Florida approximately
4,800 tung-oil trees for testing. Last winter 376 trees were dis-
tributed in seven counties. Twelve pounds of seed have also
been distributed for planting.
The Station expects, in future seasons, to continue the distri-
bution of tung-oil trees to those desiring to test them, insofar
as the Station's finances and the available supply of the trees
will permit. The Station, however, cannot undertake to supply
trees for commercial plantings. Distributions will be limited to
persons who can give proper assurances that the trees will
be planted and cared for properly, so that data concerning their
growth and production may be secured by the Station.

Bulletin 171, The Tung-Oil Tree in Florida 219

Trees and seed have also been distributed to the southern
states and California by the Office of Foreign Seed and Plant
Introduction of the United States Department of Agriculture.
So far as known, the principal method of reproducing the
tung-oil tree in China is by seed propagation. Thus far, also,
this is the only method made use of in the United States, altho it
has been determined that the trees can be readily budded and
grafted, using tung-oil tree seedlings as stock.
Mr. Mowry has found that February is the best time to plant
the seed. They should be planted about two and a half inches deep
and from 8 to 12 inches apart in the nursery row. Rows should
be not less than three feet apart to permit ample cultivation.
It sometimes happens that the seed in any given lot, particu-
larly if old, show great variability in germinating and the plants
come up irregularly. Some
nuts have been known to re-
main in the soil for three
months before sprouting.
The nurseryman, therefore,
must be careful when hoeing
small trees to avoid cutting
off those about to push thru
the surface of the ground.
The whole fruit should
never be planted. As there
are from three to seven seed
in a fruit, planting is fol-
lowed by a corresponding
number of seedlings coming
up in a cluster. Sufficient
room is not afforded for the
root system of each seedling
to develop and the resulting
trees are small and spind-
ling. Such trees do not do
: well when transplanted to
the grove. For similar rea-
sons, volunteer seedlings
which come up under bear-
Frc. 92.-Healthy and vigorous root ing trees are spindling, have
system of a young tung-oil tree.

Florida Agricultural Experiment Station

poor root systems and are generally unsuitable for grove
Tho little is known as yet concerning the fertilizer needs of
the tung-oil tree, there is little doubt but that the judicious
application of a well-balanced fertilizer in the nursery will be
found well worth while. It is suggested, however, that the ferti-
lizer be applied early in the season, applications being discon-
tinued by midsummer, in order that the young trees may harden
up before winter. Well-rooted barnyard manure, if available,
will hasten the growth of young trees.
Frequent and shallow cultivation should be given from the
time the seedlings appear until midsummer.

In general, the same methods are used in transplanting tung-
oil trees from the nursery to the grove as with other fruit or
nut trees.
In this connection, the question of the distance to plant nat-
urally presents itself. As there are no old groves of tung-oil
trees in the United States, the answer to this question is largely
problematical. On the strength of the size attained by the trees
in China some have recommended that they be planted as close
as 20 feet each way. However, it seems that this is too close for
Florida conditions where, with good care, the trees apparently
exceed in size those of China. It should be remembered that
the latter are practically uncultivated, receive little or no ferti-
lizer 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 trans-
planting alternate trees to other groves when they become
crowded. Frank Stirling, of Gainesville, successfully trans-
planted a tree six inches in diameter and several years of age.
It bore fruit the first season after transplanting. There is every
reason to believe that trees several years of age can be trans-
planted successfully, if as great care be observed, for example,
as in transplanting large citrus trees.
It is important that the trees be transplanted while dor-
mant, that is, before they begin to leaf out in spring. The trans-

Bulletin 171, The Tung-Oil Tree in Florida

planting of trees in foliage has been followed by slow growth.
In the vicinity of Gainesville, in a normal season, transplanting
should be completed before February 20.
In setting the trees in the grove, recourse can be had, in order
to secure straight rows, to the usual method of using the "plant-
ing board" (fig 93).
Mr. Mowry, who has had considerable experience in trans-
planting the young trees, gives the following directions for their
"Digging of small or one-year trees in the nursery row is best
accomplished by two men working opposite each other with
spades, each pushing his tool vertically into the soil as deeply as
possible about six or eight inches from the plant, after which,
by lifting or prying simultaneously, the whole root system is
brought up uninjured. With a larger tree it is necessary to dig

FIG. 93.-Use of planting board to secure accurate setting of trees; above,
end stakes set at proper distance from where tree is to stand; below,
tree being placed in exact position formerly occupied by tree stake.

Florida Agricultural Experiment Station

a large hole or trench alongside the tree so that the tap root can
be severed at approximately two feet below the surface of the
soil; this accomplished, the side or spread roots can be cut on
the opposite side from 12 to 18 inches from the trunk and the
whole removed without bruising. Except for cutting off the
very long roots or those broken or bruised in digging, no root
pruning is necessary. As with all plants, exposure to sun or
wind should be avoided and at no time should they be allowed
to become dry. Trees should be planted at the same depth as
they stood in the nursery row."
No pruning of young trees seems to be needed, other than
cutting off the tips of the plants; this may be done to cause more
lateral branching close to the ground. However, with yearling
trees this may not be necessary.


It is said that in China the wood-oil tree grows for the most
part upon heavy clay hillsides and in waste places; some are
found along the lower land bordering streams or valleys.
The tung-oil trees at Tallahassee have apparently done well
on the clay soils of that vicinity. At the Experiment Station at
Gainesville, however, the trees have been grown entirely upon
Norfolk sandy loam, a soil that is very sandy and naturally
rather deficient in plant food.
Further experimentation will be necessary to determine
whether the tree is adaptable to the various soil types found
in Florida. A large number of plantings have been made, so
this information is likely to be available within a few years. In
Alachua County, for example, private owners have planted the
trees upon almost every type of land found in the county. Plant-
ings have also been made at the Everglades Experiment Station,
near Belle Glade, on typical Everglades muck soil.
One thing, however, is evident, and that is that the trees re-
quire good drainage. Trees growing on poorly drained flatwoods
pine land, on which water stood for a considerable period during
the summer of 1923, were killed, apparently, by the water, altho
trees above the general level in the same planting sur-
vived. It is advisable to use land on which water will not stand
for more than two or three days after the hardest of rains.
Drainage can be facilitated also by ridging up the tree-rows,
before planting, so that there is a decided fall toward the middles.

Bulletin 171, The Tung-Oil Tree in Florida


As already stated, experiments with tung-oil trees have not
progressed sufficiently that any definite advice can be given as
to fertilization. From the tree's general habit and manner of
growth, it is certain that it will respond decidedly to fertilization.
This is particularly true in the case of nitrogen derived from
organic sources, which was illustrated in the case of a block of
nursery stock on the Experiment Station grounds. In previous
years there had been a stack of velvet bean hay near the center
of the block. At this point the nursery trees attained a height
of from eight to twelve feet, while trees of the same age a short
distance away were only from two to five feet high.
-In general it seems likely that the young trees will respond
to about the same fertilizer treatment that is given young citrus
trees. It is the opinion of several persons engaged in growing
tung-oil trees that a fertilizer containing about 5 or 6 percent
of nitrogen, 10 or 12 percent of available phosphoric acid and
2 or 3 percent of potash may give good results in the case of
young grove trees. There may be a further advantage in having
a part of the nitrogen derived from inorganic sources and part
from organic. The behavior of trees planted in old barnyards,
near poultry houses and in similar situations, shows that the
tree responds quickly to manure.
Owing to the fact that the tender growth is damaged easily
by frost or cold, it appears advisable to make the fertilizer appli-
cations during the early part of the season in order that the wood
of the trees may have opportunity to ripen before winter.
The use of cover crops, such as bush velvet beans, beggarweed
or Crotalaria, may also be found advisable, especially in young
groves. However, legumes which are subject to nematode attack
should be avoided.

As far as picking the crop is concerned, the tung-oil fruit may
well be designated a "lazy man's crop." The fruits mature in
October and November and gradually fall from the trees. 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 several weeks. In fact, the seed
will "shell out" easiest when the husks have thoroly dried
(fig. 85), in which condition they can be broken open easily.

Florida Agricultural Experiment Station

A recent publication on China wood-oil points out that this
manner of harvesting is a "very distinct advantage" to an indus-
try situated near citrus-growing districts, "where the released
labor available at the end of the citrus-picking seasons would be
accessible." Inasmuch as the citrus-picking season in Florida
extends from November to March, the value of the observation
is at once apparent.
However, when it comes to separating the seed or nuts from
the husks, considerable labor is required. No method of doing
this has yet been developed other than the simple expedient of
pulling the husks to pieces by hand and removing the seed.
Doubtless it would be a relatively simple matter to devise a
machine for doing this work.
It is said that in China the fruit is sometimes thrown into
boiling water so that the seed may be removed more readily.
This method has been tried by Mr. Mowry who finds that it does
soften the husks somewhat.
The seed, after being removed from the husk, can be stored
in any dry place for an indefinite period. However, if the seed
are to be used for planting, they should not be carried over from
one season to another, but should be planted during the winter
following the autumn in which they drop from the trees.
The principal product of the tung-oil tree is the oil, which is
expressed from the seed. The amount of oil in the meat (seed)
seems to vary from about 33 to 49 percent by weight. Oil of
fair quality is light golden or light amber in color and, when
free from impurities and of good quality, is nearly transparent.
As a rule, not more than three pounds of seed are required for
the production of a pound of oil.
There are, of course, no commercial plants in America as yet
for the extraction of oil from tung-oil seed, as the present annual
production probably does not exceed 1,000 pounds of seed. From
American-grown nuts the oil is, however, readily extracted by
means of small laboratory presses or even by oil-mill machinery,
such as is used for the expression of other vegetable oils like
cottonseed oil, peanut oil, etc. At present the seed are in demand
for planting, as well as for experimental work by paint and
varnish manufacturers who are finding that the oil from Florida-

Bulletin 171, The Tung-Oil Tree in Florida

grown nuts is of higher quality than the imported oil and that
it lends itself to a wider variety of uses.
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:
Maximum Minimum
Specific gravity at 15.5C................................. 0.943 0.939
Acid number (alcohol-benzol) ............................. 7.0
Saponification number .......................................195.0 190.0
Unsaponifiable matter, percent ....................... .76 ...-
Refractive index at 250C. .............................. ... 1.520 1.515
Iodine number (W ijs) ...... ............... -- .. -...... .... 163.0
A. S. T. M. heating test, minutes ................ ... 12.0......
If the culture of the tung-oil tree continues to develop in Flor-
ida and adjoining states, seed probably will be in steady demand
for planting purposes for a number of years, and as such may
command a higher price than would be justified on the basis of
its use for oil making. It is only upon the latter basis, of course,
that a permanent industry can be built. Certain aspects of this
are discussed on another page, under the head of "Probable
The husks removed from the seed after harvesting, contain,
according to Mr. Hardee's analysis, only about six-tenths of
one percent of available ammonia. Hence, so far as fertilizer
value is concerned, the husks are practically worthless. How-
ever, their return to the soil may add appreciably to its humus
content, and from this standpoint their distribution upon culti-
vated, sandy soils is doubtless justifiable.
The pomace, or residue remaining after extraction of the oil
from the seed, has a fair fertilizer value. Mr. Hardee found
the pomace to contain 5.66 percent available ammonia, in which
respect it compares well with castor pomace which is used
rather widely as a source of organic nitrogen in fertilizers.
Castor pomace, containing about 6 percent available ammonia,
is being quoted by retailers at from $30 to $33 a ton.

The fact that the blossoms are not infrequently killed by early
spring frosts in the states north of Florida, coupled with the
"Submitted by Henry A. Gardner. of the Institute of Paint and Var-
nish Research, and taken from Miscellaneous Series-No. 125, Department
of Commerce.

Florida Agricultural Experiment Station

fact that trees at Tallahassee suffered rather severely from cold
during 1917, while the trees at Gainesville experienced little,
if any, damage, seems to indicate that from the standpoint of
climate central Florida is as well adapted to the culture of this
tree as any locality where it has been tested.
Few trees have, as yet, been planted south of Marion County.
Therefore, the tree's behavior under conditions existing in the
southern part of the state is unknown. In this connection, how-
ever, it must be recalled that most of the well-drained lands in
the southern part of the Peninsula are high-priced, due to their
use for growing citrus, avocados and other sub-tropical crops.
As will be pointed out below, the returns from wood-oil trees
will hardly warrant their culture on land that costs from $150
to $300 an acre.
In recent publications concerning the tung-oil tree, the direc-
tor of the Florida Experiment Station has been quoted as saying
that the tung oil tree is less subject to disease and insect attack
than any other tree in Florida of which he has knowledge. In
this he was not quoted correctly. He has stated, however, that,
so far as his observations indicate, the tung-oil tree, during its
introduction into America, apparently has not been accompanied
by any of the insects or diseases which may affect it in its native
Chinese home. This, in fact, appears to be the case.
Few plants of economic importance have been imported from
foreign countries without the importation with them of some of
their diseases or insect enemies. If the tung-oil tree has left
its natural enemies behind, it is indeed a fortuitous circumstance
and one which lends encouragement to the view that its culture
can be made profitable in America.
However, no growing plant of any kind is known to be entirely
immune to the attacks of parasites, either insect or fungous. It
is naturally expected, therefore, that when a plant is introduced
into a new country the insects and other plant parasites already
there will in some measure adapt themselves to the new plant.
This is apparently taking place in the case of the tung-oil tree
in Florida. Up to the present time one root parasite, the nema-
tode, and two species of scale insects have been found attack-
ing it.

Bulletin 171, The Tung-Oil Tree in Florida

(Heterodera radicicola (Atkinson))
In the case of tung-oil nursery trees, grown on old cultivated
land at the Experiment Station at Gainesville, the roots of a
considerable number have been found infested in varying de-
grees with the nematode. This parasite causes the trouble known
as root-knot. Trees so affected were observed for the first time
by Mr. Mowry on February 24, 1923. Root-knot affected roots
of a tung-oil tree are shown in figure 94. In some cases, par-
ticularly in fields known to be heavily infested, the effect of the

FIG. 94.-Roots of young tung-oil tree severely affected with nematode
root-knot. Compare healthy roots shown in figure 92.

Florida Agricultural Experiment Station

nematode has been pronounced; young seedlings have failed to
make a normal growth, while in other cases they have been
apparently killed. This trouble has not been perceptible where
the seed were planted in new land or in land which had been
in grass for one or two seasons previously.
Strict rejection of all nursery trees showing nematode infesta-
tion at digging time, coupled with the planting of groves on
newly cleared land or on land that has not grown hosts of the
nematode for two or three seasons previously, would seem an
adequate measure for preventing serious losses from this para-
site. Perhaps it would be well, as an added measure of safety,
to grow as cover crops in tung-oil tree groves only those plants
known to be immune to or highly resistant to the nematode;
such as Crotalaria, beggarweed and velvet beans.
It is not felt that the effects of the nematode upon tung-oil
trees under the conditions cited will prevent the successful
growth of these trees in Florida. The nematode attacks a great
number of trees and plants2", and some of those which are sub-
ject to rather heavy attack are, by using proper precautions,
grown with profit. The very fact that the susceptibility of the
tung-oil tree to root-knot is known makes it possible to take pre-
cautions against this trouble. For more complete information
concerning nematodes and their control the reader should con-
sult Bulletins 136 and 159, by J. R. Watson, of this Station.

(Icerya purchase Mask.)
In January, 1923, this scale-insect was found on tung-oil
trees in the Experiment Station grounds and since has been
found from time to time on both young and old tung-oil trees
there. Severer infestation has not appeared upon the tung-oil
trees than upon other host plants of the scale, such as citrus,
growing in the same vicinity.
The cottony cushion scale is not viewed with any particular
alarm by Florida horticulturists, owing to the readiness with
which it is controlled by the Australian lady-beetle and there is
no likelihood that it will be any more injurious to tung-oil trees
than it is at present to citrus and many shade and ornamental

"oA comprehensive list of the host plants of nematodes will be found in
Circular 50 of the State Plant Board, which may be obtained by addressing
the Board at Gainesville, Florida.

Bulletin 171, The Tung-Oil Tree in Florida

trees". However, when nursery trees are found infested with it
at digging time, all the trees should be scrubbed thoroly with a

FIG. 95.-Cottony cushion scale, Icerya purchase Mask.
(After Wilson, Quarterly Bul., State Plant Board of
Florida, Vol. II, No. 1.)

solution of whale-oil soap, otherwise more or less isolated grove
plantings may experience a severe increase of the scales before
the latter are found by the lady-beetle.

"A list of host plants of cottony cushion scale will be found in-Circular
50 of the Florida State Plant Board.


Florida Agricultural Experiment Station

(Aspidiotus lataniae Sign.)
This scale-insect, which is of quite common occurrence on
palms and Australia pines" in Florida, has been found by Ed
L. Ayers and Harold Mowry in
small quantities on tung-oil
trees. Its economic importance
is questionable. It can be con-
trolled easily by proper spray-
ing practices and frequently is
kept well under control by


Many factors bear upon the
question of probable financial
returns from the production of
tung-oil seed in Florida. Data
are not at hand upon which to
presage safe estimates. The
S cost of production can be de-
termined only by actually
growing the trees upon a com-
mercial scale over a period of
years. The average production
of trees under Florida grove
FIG. 96.--Latania scale, Aspidiotus conditions is as yet unknown
lataniae Sign. (After Wilson, Quar-
terly Bul. State Plant Board of and there are no data available
Florida, Vol. II, No. 1.) as to the maximum crops which
may be produced from single trees or as to the life of the tree
itself. The market price for tung-oil in future years also will
have a most vital bearing on the question of whether or not
culture of the tree will be profitable.
At the same time, the reader no doubt will wish to know what
data, however meagre, are available on the question. The only
estimates of this character which can be made must of necessity
be based upon the behavior of the few bearing trees in Florida
at the present time. Perhaps the production of the 10 trees (10,
and 12 years old) on the Experiment Station grounds at Gaines-
ville afford as safe a criterion for such speculations as any.
"Casuarina sp.

Bulletin 171, The Tung-Oil Tree in Florida

The production of these trees in 1922 was, in round figures, 9
pounds of shelled nuts or seed to the tree; and in 1923 it was
18.5 pounds to the tree. The average for the two years was 133/
pounds. On the basis of 70 trees to the acre (planted 25x25 feet),
a production equal to the above average would mean an acre
yield of 9621/2 pounds.
Any price for the seed, based upon their demand for planting
purposes, is temporary, necessarily: the permanent value of the
crop will depend on its value for oil production. In this case
the value of the crop will vary directly with the price of the oil.
According to William A. Taylor23 the market price of the oil,
American basis, has not gone lower than 8 cents a pound during
the last ten years. Prior to the World War the price was usually
in the neighborhood of 12 cents. The highest price reached in
recent years was in May, 1923, when it went as high as 45
cents. During 1923 the domestic price rose from 14 cents in
January to 45 cents in May, after which it declined more or
less steadily to 22 cents in October23. As an "estimate" it may
be well to use the approximate minimum price of the last ten
years, namely, 10 cents a pound.
The theoretical crop of 962 pounds of seed to the acre from
trees 12 years old, would produce approximately 321 pounds of
oil, as one pound of the latter is secured from about three pounds
of seed. On the basis of ten cents a pound, this production would
give a gross annual return of $32.10 an acre. From this must be
deducted the cost of expressing the oil and its transportation to
consuming centers. However, it is the opinion of those who have
studied the subject that the latter charges will be about offset
by the value of the pomace, or residue after extraction of the
oil. So, for practical purposes and until more data are ac-
cumulated, the value of the oil may be considered as the probable
return to the grower.
Of course, many factors may enter into such a computation.
For example, the average production of 133/ pounds to the tree
is a two-year average, one year (1922) of which showed a pro-
duction probably far below normal, as evidenced by the wide
difference in production of these trees in 1922 and 1923. It is
also true that the trees in question are growing too close to-
gether (10 feet apart) for maximum production. On the other
hand, they are far better protected from storms and winds than

"Department of Commerce, Miscellaneous Series-No. 125.

Florida Agricultural Experiment Station

would be trees in the average grove planting. They also have
been protected from floods, fires and soil erosion. It is true also
that some of these trees are scanty producers and that a grove
of trees from selected stock naturally would give a much higher
average yield. Trees under cultivation might produce larger
crops: then they might not. The proper and liberal use of ferti-
lizer might result in a pronounced increase in yield, but as yet
there has not been time in which to demonstrate this.
As can readily be seen, the market value of oil directly influ-
ences the acre returns. With oil at 20 cents a pound, for example,
a production of 962 pounds of seed would mean a return of
$64.20; at 30 cents a pound it would mean $96.30; etc.
At first sight, a crop yielding a probable minimum acre return
of $32.10 may not appear attractive. In this connection, how-
ever, it must be remembered that this estimate is based upon
the production of trees which, in recent years at least, have
received neither fertilizer nor cultivation and that the harvesting
of the crop does not call for high-priced or skilled labor. Also
packing-houses for grading the seed are not necessary and
the product does not have to be wrapped in tissue paper and
hand-packed in expensive boxes. The fact that the crop is not
highly perishable-it is, in fact, almost a staple in this regard-
warrants consideration.
It must be recalled, also, that a return of $32.10 an acre is
decidedly above the average annual return from field crops grown
in Florida". If the farmer can afford to grow corn, peanuts,
hay and cotton for this figure, he probably can grow tung-oil
trees also, particularly as he would not have to purchase seed
and plant his fields every year.
One should not draw the conclusion that the tung-oil tree can
be planted out and then neglected, if financial returns are to be
expected. On the contrary, good care and cultivation are neces-
sary to get an orchard well established. Thereafter the trees are
likely to respond to good care, cultivation and fertilization; and,
as with other horticultural products, the yield is likely to be
directly proportionate to the care given.

"According to statistics given in the Seventeenth Biennial Report
(1921-22) of the Florida Department of Agriculture, the average acre
values of certain farm crops common to central and northern Florida for
the year 1922 were as follows: upland cotton, $16.28; Sea Island cotton,
$22.97; corn, $8.82; peanuts, $17.63; field peas, $14.30 and peavine hay,

Bulletin 171, The Tung-Oil Tree in Florida

It is not the writer's belief that any fabulous fortunes will be
made from growing tung-oil trees in Florida. On the contrary,
it is more likely that the production of tung-oil nuts will be
found to yield the most satisfactory returns on the small or
average farm, where their production is made part of a well-
ordered farm practice and management. Nearly every farmer
in central Florida has lands lying idle which appear suitable for
this purpose. He can find time to plant and care for a few acres
of the trees without perceptibly adding to the annual cash outlay
for operating his farm. Much of the work necessary in preparing
land for planting and in caring for the groves after planting,
as well as the harvesting and shelling of the seed, can be done
by himself and members of his family without interfering with
other crops, livestock, etc. The addition of another crop, in the
form of tung-oil seed, even tho the acreage return is not large,
would tend toward insuring a satisfactory cash balance at the
end of the year and would still further remove from the farmer's
operations the hazards which attend a farm practice based
largely upon the production of only one or two crops.


The following paragraphs answer briefly the questions most
frequently asked concerning the tung-oil tree and its products:
Importation of tung-oil into the United States, 1922, was
79,089,292 pounds."
Total exports of tung-oil from China,. 1922, were 745,565
piculs (99,383,814 pounds)."
A picul equals 133.3 pounds.
The price (domestic) range of tung-oil from January 1, 1920,
to October 15, 1923, was from 9 to 45 cents a pound."
There is no tariff on tung-oil.
Price of oil, April 15, 1924, $1.36 a gallon.
One hundred pounds of fully matured and thoroly dried fruits
consist of about 56 pounds of seed and 44 pounds of husk.
From 92 to 114 seed or shelled nuts are required to make
a pound.
The percentage of oil in the seed, by weight, ranges from 33
to 49 percent; usually about 33.3 percent.
One gallon of tung-oil weighs eight pounds.
Pomace, secured in extraction of the oil, equals about two-
"Department of Commerce, Miscellaneous Series-No. 125.

Florida Agricultural Experiment Station

thirds the weight of the seed. The pomace contains from 5.5
to 6 percent of available ammonia.
Planting distances recommended: 25x25 feet, 25x30 feet or
121/2x25 (or 30) feet, the last distance being used with the expec-
tation of removing or transplanting alternate trees in future
Florida grove plantings of tung-oil trees in the spring of 1924
are estimated at: bearing trees, 3,307; non-bearing, 35,878;
total, 39,185.


In connection with the preparation of this paper the writer
is under obligations to Dr. K. F. Kellerman, Dr. David Fairchild
and Mr. R. A. Young, all of the Bureau of Plant Industry,
United States Department of Agriculture, for information gen-
erously supplied from the files of that department, particularly
as related to the introduction and distribution of Aleurites trees
in the United States; to Henry A. Gardner, of the Educational
Bureau of the Paint and Varnish Manufacturers Associations,
for various items of technical information; to Mr. B. F. William-
son, of Gainesville, for access to the rather voluminous records
and notes which he has been able to collect with reference to
the tung-oil tree; to Mr. Geo. B. Merrill, of the State Plant
Board of Florida, for the identification of insect specimens; and
to Messrs. Ed L. Ayers and Harold Mowry, of the Experiment
Station, for various observations, notes, references, photo-
graphs, etc. To Dr. A. F. Camp, of the State Plant Board, of
Florida, acknowledgment is made for a number of the illustra-
tions appearing herein.

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs