FATE OF FLORIDA.. DEPARTMENT OF AGRICULTURE
, Nathan Mayo, Commissioner . Tallahassee
An Essential Defense Industry
O. 11 NEW SERIES
Compiled by Workers of the Writers' Program
Work Projects Administration
State of Florida
BRIG. GEN. PHILIP
B. FLEMING, Administrator
WORK PROJECTS ADMINISTRATION
HOWARD 0. HUNTER, Commissioner
FLORENCE KERR, Assistant Commissioner
WILBUR E. HARKNESS, State Administrator
PUBLISHED BY THE STATE OF FLORIDA
DEPARTMENT OF AGRICULTURE
NATHAN MAYO, Commissioner
TABLE OF CONTENTS
In tro d u ctio n ....................... ........ ...... . ...... .. ... .............. ............... 5
T u n g O il..... ......... ........... ........ ...... .. ................. ......... 9
U ses of T u n g O il......... .......... .. ... ........ ...... ........ .. ................ 11
Climate and Soil Requirements................. ............... .... ....... 14
Soils for Tung Trees .... ....................... ............................................. 17
Best Locations for Tung Trees....................................................... 26
Preparing Land for Tung Trees...................................... ......... 29
Planting and Maintenance ........................................ ........................ 33
Harvesting and Marketing.......... ....................... ......................................... 38
Oil Extraction Methods................................. ....... .............................. 40
Hazards for Tung Culture .............. ................................................ 41
Production of Tung Oil in Florida................................. .............. 44
Tung Oil Importations................... ............ ................. ......... ............... 47
A p p e n d ic e s ......................................... ......................... ..... ........ ......... ......... 4 8
Reference Information ......... ..... ........... ...... ....... ...... 51
DEPARTMENT OF AGRICULTURE 5
The tung tree is a native of China, and for many centuries
thrifty and industrious Chinese farmers have extracted a
valuable commercial oil from the seeds that are encased
within its five kernels in the normal alerities Fordii nut.
In 1905 the United States Department of Agriculture
imported 200 lbs. of tung seed from Consul General Wilcox
of Hankow, China and planted them at its plant introduction
station in Chico, California. Many hundreds of the seeds
took root and, in 1906, the growing seedlings were distributed
to a number of State experiment stations, principally South-
ern ones, that lay between the latitudes of 250 and 34 north.
The latitude of this region roughly corresponds to that of the
Yangtze Valley, where China's tung crop is grown. The
experiment stations agreed to cooperate with the U. S. De-
partment of Agriculture by cultivating the seedlings.
In 1906 five of these seedlings were sent to the superin-
tendent of the old City cemetery at Tallahassee and he in.
return gave them to William H. Raynes.
Records show that in spite of the careful nursing of the
five trees, all but one died and on March 24, 1907, a severe
gale nearly destroyed this one and it had to be cut back to
a height of three feet.
Raynes kept careful notes on his tree and reported that
in 1908-just "three years from the planting of the seed
nuts in Chico, Calif.," the tree blossomed and produced three
In 1909 the tree produced 64 fruits and in November of
that year, Raynes planted them and grew other trees which
he later distributed to friends.
The now famous Raynes tree produced 88 fruits in 1910
and 344 in 1911. At this point Raynes sent to the agriculture
department at Washington 286 fruits, or a bushel of unshelled
seed and according to the 1935 bulletin of the University of
Florida experiment station on The Tung Oil Tree, this was
the first bushel of tung oil nuts produced in America.
The tree withstood a severe freeze in 1911 and came out
with a heavy bloom in April of 1912. That year the tree
6 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
produced 852 whole fruits, which Raynes sent to Washington,
and had a circumference of 24 inches at a point 12 inches from
the ground and the spread of the branches was 23 feet.
During 1913 Dr. Tenant Ronalds, who had purchased the
old Live Oak plantation, became interested in the tung oil
tree and planted four acres from seedlings which he obtained
from Raynes. Ronalds' grove consequently became the first
bearing tung oil grove in Florida and, as far as records show,
in the entire United States.
Dr. Ronalds took great pride in his small grove and in-
creased the acreage to 40 in 1915 but another severe freeze
occurred in 1917 and the young nursery stock and young trees
were killed. Thereafter for several years no care was given
the planting except that it was pastured and occasionally
However, in 1925 B. F. Williamson was given permission
to cultivate the grove and from a partial rejuvenation of the
trees he was able to obtain enough seeds to start a large grove
near Gainesville. Williamson is credited by Dr. Fairchild
with being the first person to start a large planting of the
trees in America.
In 1913, the year that Dr. Ronalds started his four-acre
grove, the original Raynes tree produced 1,095 fruits, accord-
ing to the planter's own notes, and from these fruits he was
able to obtain a bushel of shelled seeds. These he sent to the
Educational Bureau, Paint Manufacturers' Association of the
United States and from them 2.2 gallons of oil-the first
American-grown tung oil-was produced.
Raynes died November 12, 1914. Shortly afterward his
old home burned and the original tree, being nearby, was
severely injured but managed to survive its burns.
In later years, during which Williamson became interested
in the old Ronalds' grove on Live Oak plantation, the Raynes
tree grew to a height of 27 feet and the trunk had a circum-
ference of 52 inches at a distance of one foot from the ground
In 1923 it produced about 150 pounds of whole fruit. That
was the last year that production records were tabulated,
as far as is known.
A small plot around the Raynes tree was leased by the
United States department of agriculture and the tree was
protected from live stock by a special iron fence.
DEPARTMENT OF AGRICULTURE 7
However, the department allowed the lease to lapse in
1933 "when economy measures were being put into effect
quite intensively." And according to local experts, another
federal agency hurried the death of the 'pioneer' by butcher-
ing it to the main stems and moving it approximately 30 feet.
Since then the tree has gradually died and now is nothing
more than a rotting shell of its former self.
Quick to see the possibilities of tung oil as a new Ameri-
can industry, the Florida Agricultural Experiment Station
at Gainesville undertook intensive tree propagation, recording
excellent results in northern and north central Florida where
the most favorable conditions in climate and soil exist. These
experiments led to extensive commercial plantings, beginning
in Alachua County in 1923, and spreading rapidly through
Levy, Clay, Jefferson, and Okaloosa Counties, with smaller
plantings in other central and north Florida counties.
A Growing Part of Our Industrial Economy
It is only in recent years that tung oil has had a place
in America's industrial economy, but in that time it has
become indispensable. This country has used all the tung
oil it could get from China, in spite of the fact that fluctua-
tions have existed in tung oil prices and supplies. It seems
that the United States must have tung oil at any price, espe-
cially now that the war has shut off all imports.
America still has much to learn about the culture of tung
trees for the commercial production of their oil. Only a
trickle of the oil has been coming from China recently and
even this has ceased to flow because of war conditions. This
stoppage has thrown America on its own in the production of
Florida, the birthplace of America's tung oil industry, is
far from producing adequate commercial quantities of the
oil, but is, with other tung sections of the South, steadily
increasing its output. Tung oil is one of Florida's newest
industries, and although not among the State's more im-
portant and successful enterprises, production of tung oil in
some sections of Florida, nevertheless, has already emerged
from the chrysalis of experiment to become an agricultural
and industrial asset.
The demand for tung oil is far greater than the supply,
and the price is high. "The amount so far produced in this
country," says Dr. C. C. Concannon, industrial consultant of
the United States Department of Commerce, "has been but a
small fraction of our total annual consumption in recent
years, which has been more than 100,000,000 pounds." Dr.
Concannon. states that "Tung oil is selling at higher prices
than any other drying oil necessary in the paint and electrical
industries and is finding an eager market."
The annual oil crop is regarded as a national asset, as
well as an item of importance in the economy of the Southern
States. As an industrial product, it plays a prominent part
in the growing industrialism of the South. For instance,
tung oil and rosin combine to produce a good varnish.
Rosin, also produced in the South, is readily accessible to
10 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
tung producing areas. Tung oil is regarded as being of
importance to our national defense by the Office of Pro-
duction Management and other defense agencies, but whether
or not it is to be regarded as "vital" has not been ascertained.
During the past 10 years tung trees have been planted
on approximately 175,000 acres of land in the United States.
A large percentage of these trees may never bear fruit, in
the opinion of Dr. Concannon. In fact, some of the acreage
has already been abandoned. "Whether we now have as
much as 50,000 acres actually producing, or definitely in line
to be producing, is a question in my mind," stated Dr. Con-
A demand for tung oil in excess of the supply has created
a situation that is challenging the ingenuity of chemists and
technicians who are driving to produce a satisfactory substi-
tute. Several have been attempted and a few are said to
be in use. But the Department of Commerce on June 17,
1941, stated "Despite considerable scientific research, as yet
no oil with the equivalent desirable qualities of tung oil has
yet been found." Whether or not a suitable substitute for
tung oil will be found is regarded as problematical. With
the scarcity of tung oil and the high price it commands, the
incentive to chemists and technicians to produce a synthetic
substitute is enormous.
During the first six months of 1941, 15,767,576 pounds of
tung oil were imported from China, the prices ranging from
25 cents to more than 30 cents a pound. The South produced
approximately 5,000,000 pounds in 1940.
This country normally consumes over 100,000,000 pounds
of tung oil a year, but produces only 5,000,000 pounds during
the same period of time. In addition to the established de-
mand for tung oil, large quantities are needed by the Navy
and for use in paints for airplanes, tanks, and guns, and for
waterproofing cartridge shells.
Uses of Tung Oil
As a waterproofing material, nothing as satisfactory as
tung oil has been found, although several substitutes have
been attempted, some of which are in use.
Tung oil's waterproofing qualities were utilized centuries
ago in China, where it is still used for the waterproofing of
masonry, cloth, shoes, clothing, paper, umbrellas, and re-
ceptacles for liquids. Crude grades are used for the water-
proofing of Chinese junks. The Chinese even utilize the
residue of the tung nuts, by burning and mixing it with the
oil, to form a paste for caulking boats. This residue is also
used in manufacture of lampblack and Chinese ink, commonly
known as India ink and used by draughtsmen the world over.
The introduction of tung oil, or Chinawood oil, into
America brought changes in the manufacture of varnishes
and products with varnish as an ingredient, which until then
had been manufactured from a basic combination of linseed
oil and imported fossil gums, the supply of which was rapidly
decreasing. The paint industry discovered that tung oil in
combination with rosin, produced a resultant product of such
quality that it was possible for manufacturers to dispense
with the imported fossil gums.
When used in varnishes, tung oil tends to make the
product waterproof and also reduces its liability to crack.
It is claimed that no varnish which will not turn white under
exposure to water can be made without the use of tung oil.
It is unmatched for waterproofing and is one of the best
Tung oil is responsible for China's famous waterproof,
glossy lacquers which so largely feature their temples and
the interior decorations of other buildings. Paints that con-
tain tung oil give a much glossier finish than other paints
and seem to be more resistant to fungus attack. For these
practical reasons, tung oil has been supplanting linseed oil
in ordinary paints.
A vital ingredient in the manufacture of varnishes, paints,
lacquers, enamels, and fillers, tung oil is also used in the
manufacture of linoleum, oil cloth, automobile top dressings,
and several other products. The oil is used as a dressing for
12 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
leather and in the manufacture of soap. Fatty acids from it
are utilized in making lacquer or substitutes for shellac, and
in combination with rosin, waterproof- or spar-varnish. With
aluminum oxide it is made into aluminum tungate, used in
waterproofing numerous articles.
The U. S. Office of Production Management announced to
the Nation on January 8, 1942 that all American stocks of
tung oil had been placed under priority control. This meant
that the dwindling supply could only be used in essential
defense industries, unless otherwise permitted by OPM. Under
the ruling, much of the oil will continue to go into weather-
proofing for cartridge shells and various types of fabrics,
including raincoats. The electrical industry needs it as an
essential quick-drying agent in the manufacture of insulating
compounds for dynamos, cables, and wire coatings. It is
also needed as an ingredient for brake linings and for use in
the gaskets of steam pipes, pumps, and engines.
Tin cans have long been manufactured of steel, with only
thin inner and outer coatings of tin. A few years ago many
factories began making cans without the use of tin. These
are composed of steel with coatings of copper or waterproof
enamel, the latter containing a large proportion of tung oil.
This innovation was brought about by the threat of a tin
shortage. World conditions made apparent the fact that war
against the Fascist nations would imperil American imports
of raw tin from the Far East and Chile, as well as imports
of sheet tin from English processing plants. Tin was placed
on the OPM priority list even before war began, thus exacting
further demands on the American supply of tung oil.
Inasmuch as the tung industry is only about 25 years old
in this country, it is not known how long a tree will live here,
but there is no reason to believe that its life here will be
shorter than in China, where its productive life is said to
range from 30 to 50 years.
The type of tung tree that is grown in this country belongs
to the spurge family and is botanically classified as Aleurites
fordi, known to the Chinese as Tung-yu-shu.
The mature tung tree is about 30 to 50 feet high and its
branches spread equally in all directions. It drops its leaves
in November and leafs out again in March or early April.
DEPARTMENT OF AGRICULTURE
The blossoms, appearing with or before the leaves, are of two
kinds. Both the staminate and pistillate types are borne
on the same tree, hence the tree is self-pollinating.
It is a mistake to speak of the product of the tung tree
as nuts, although when dry, they have the hardness of nuts.
Instead, they are fruit. The fruit ripens in October and
November, and when mature, drops from the tree. This
obviates the cost of picking. Harvesting costs, as a result,
are quite low.
In appearance and shape, the fruit resembles a small
apple, the diameter being from two to three inches and the
color olive green. At maturity the color changes to a brown.
Normally there are five seeds in each fruit. The hull is tough
and leathery and becomes quite hard when thoroughly air-
Florida growers have not yet generally taken to naming
their varieties, although several variations among the seed-
lings are apparent, this mainly having to do with the size
and shape of the fruit, variation in leaf shapes and blossom
color, and the number of individual fruits borne at the twig's
end. This has led to the general designation of two types-
single and cluster. Cluster-bearing appears to be an inherent
characteristic, in which case it is advantageous to plant this
type so as to secure heavier yields.
Climate and Soil Requirements
The climate and some of the soils of Florida seem to be
especially favorable for tung production. Because of the
relatively short period of tung culture in this country, much
has to be learned of the tree's adaptability to various soils
and climatic variations. Even with ideal climatic conditions,
the tree does not thrive on all soils. From experiments, it
has been ascertained that the best growth is obtained on soils
which are slightly acid in reaction, which have plenty of mois-
ture, but are thoroughly drained, and have no excessive
amount of phosphate or lime. Alkaline soils are detrimental
to tung growth. The tung tree, to a large extent, thrives in
direct proportion to the richness of the soil in which it is
planted. It relies upon good drainage more than upon any
other physical condition. In this connection Joseph C.
Adderley, author of American Tung Tree, says:
"The top surface should be gently rolling or sloping and
must provide a good surface drainage. Avoid low, flat land,
or land which may be subject to overflow. It is also advisable
to select land which is not too sharply rolling and which may
cause erosion difficulties. Land that is moderately rolling
may be successfully used for tung tree groves by means of
contour planting and terracing.
"Good air drainage too is an important consideration in
selecting land for tung tree production. High land is prefer-
able to low land. Air currents flow much like water and
follow the same general contours. Low spots, particularly
low pockets, should be avoided, as they always present the
greatest possibility of cold damage.
"A clay base subsoil is desirable for tung trees. Prefer-
ably the clay base would be of a loamy character which will
not form a hardpan. A clay subsoil prevents the leaching
out of soil nutriments due to excessive rainfall, and makes
for economy in the use of fertilizers. It also provides a firm
anchorage for the tree and permits it to resist wind damage.
The texture of the subsoil should be such as to retain mois-
ture, but nevertheless should provide for good undersurface
"The ideal soil for tung trees consists of a top sandy loam
with high organic matter content. Such a surface is more
DEPARTMENT OF AGRICULTURE
easily cultivated and kept clean than a heavy top clay soil.
The ideal subsoil consists of a clay or clayey loam with a
relatively high collodial content. The following soil classi-
fications have given excellent results for tung tree growth
and tung nut production: Orangeburg, Tifton, Ruston, Sus-
quehanna, Norfolk, and other soil classifications of similar
Although the largest mature plantings are in Florida,
extensive tung acreages exist in Mississippi, with lesser acre-
ages in the southern parts of Georgia, Alabama, Louisiana,
and southeastern Texas. The northern and southern limits
for successful culture have not yet been defined. Climatic
requirements apparently restrict plantings to the area from
Florida, west to eastern Texas, and approximately within 100
miles of the ocean or the Gulf.
From a report of the Farm Credit Administration (1935),
conflicting accounts were received as to winter killing and
frost damage to blossoms of existing groves in the South.
Because of the high percentage of trees outside of Florida,
not yet at commercial bearing age, and because of the in-
herent variability in the period of dormancy of trees, it was
not possible at that date to determine accurately the weather
hazards in the various other areas of the South. Several
years' records of yields of mature commercial groves will
b- necessary before these hazards can be determined ac-
At Gainesville mature trees and nursery stock have under-
gone a temperature of 150 F. without apparent damage. In-
jury from freezing depends largely on the condition of the
tree at the time. If in only a partially dormant condition,
as for instance during fall or spring, damage might result
from low temperatures that would have no ill effect on trees
completely dormant. As the blossom season occurs during
the last week in March and the first week in April, the
trees at this time are susceptible to frost damage, which
would injure the fruit. The northern boundary is therefore
limited to the area which is not frequently subjected to frosts
during this period.
Southern limits for plantings in Florida have not defi-
nitely been established. In the main, however, poor results
have attended the plantings in south Florida. But in the
16 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
majority of cases it has been difficult to separate the effects
of soil conditions from the effects of climate. Being decid-
uous, the tung tree seems to require a sufficient period of
cold, to cause the leaves to drop, and a period of dormancy
during the winter.
Mr. Adderley says that a full three months' period of
complete dormancy is required for the tung tree. During
this period the tree defoliates and is at rest. The southern
boundary is therefore limited to such areas as have tempera-
tures sufficiently and consistently low throughout the months
of December, January, and February to keep the trees in
dormant condition. The range of desirable temperature
(Fahrenheit) during the winter season will be from 30
minimum to 70 maximum and with an average minimum
of 450 and an average maximum of 60 for the three winter
months. In regions too far south a warm spell during these
winter months may cause the sap to rise and, if followed by
freezing temperature, injury to the tree results.
Considerable sections of Florida are unsuitable for tung
culture because of the more or less exacting requirements of
both soil and climate. Thus far it has been demonstrated
that the most propitious areas are confined to the ridge sec-
tion of north and north central Florida. In addition to a
variety of tested soils, a water table low enough to keep the
roots from reaching standing water at any time is desirable.
In every instance the task of not only analyzing, but of
drilling the soil should be followed. Except to the initiates,
surface indications are not always dependable but are often
It was stated by B. F. Williamson, chairman of the Florida
section of the American Chemical Society, in 1937, before a
meeting of the Chemurgic Conference, in Gainesville, that:
"Looking over the whole area of Florida, we find that some
soils in the western area are more fertile than some soils in
the eastern area, where tung oil is produced. In this con-
nection the climatic condition must be taken into considera-
DEPARTMENT OF AGRICULTURE 17
Soils for Tung Trees
In Circular No. 622 of the National Paint, Varnish and
Lacquer Association, Inc., issued in May 1941, Matthew
Drosdoff, associate soil technologist of the Division of Fruit
and Vegetable Crops and Diseases, Bureau of Plant Industry,
U. S. Department of Agriculture, made these statements:
"When one considers the total investment in a tung
orchard over a period of say 20 years, it is sound business
practice to spend a little time and money in the selection of a
suitable site, with particular attention to the soil type. Once
the orchard is established, and operations begun, there is
little chance of withdrawing without large losses if one finds
it on an unsuitable soil location. In general farming one has
greater opportunity for changing the cropping system in the
event the soil is found to be unsuited to certain crops and a
mistake in the selection of soil is not so serious, though it
may be bad enough. Therefore one should be most exacting
in selecting a soil for his tung orchard, for once his choice is
made, it is difficult to back out.
"There are a number of characteristics that a soil must
have to meet the fundamental requirements of crop plants.
Many of these characteristics are interrelated and the influ-
ence of any one of them depends upon the others. Adequate
aeration and drainage, adequate moisture and nutrient stor-
age capacity, sufficiently high nutrient level, suitable reaction
of pH, favorable topography with regard to both the use of
cultural implements and soil erosion are some of the more
important requirements. Crops are sensitive in different de-
grees to some of these conditions. For example, certain crops
will grow well in very acid soils whereas others cannot. Yet
it is well established that with few exceptions cultivated
crops will grow best on soils that are just slightly acid, pH
about 6. Again, certain cultivated crops are more sensitive
to impeded drainage than others though admittedly a well
drained soil is generally required for optimum growth. This
sensitivity to drainage conditions is one of the most im-
portant factors in differentiating field crop soils from soils
suitable for orchard crops. In general, orchard crops are
more sensitive than field crops to impeded drainage. One
reason for this is the deep permanent root system of the trees
as contrasted to the shallow roots of annual field crops.
18 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
"Here then is one of the big differences between orchard
crops and field crops-length of time of residence-which is
of utmost importance. It is for this reason that careful
attention should be given to the soil factor in the selection
of an orchard site. In the past it has been the practice of
some to locate the orchard on soils where other crops did
not do so well, the idea being that the trees could get by
where the field crops couldn't. Perhaps under some ex-
ceptional circumstances this worked out, but we now know
that orchard crops are much more exacting in certain soil
requirements than are field crops.
"It should be pointed out that certain soil characteristics
can be easily changed by man without too much expense,
whereas, others can be changed little, if at all, or only at a
prohibitive cost. Therefore, it is necessary to pay more at-
tention to certain characteristics than to others in selecting
a soil, though they may all be of equal importance as far as
the tree is concerned. Another point to be emphasized is
that when we speak of certain soil types we are not merely
referring to the top six inches of soil. A soil is actually com-
posed of several layers or horizons down to a depth of several
feet and the lower horizons are just as important as the
upper horizons in determining the characteristics of soil.
This is especially true when one is considering an orchard
crop with its deep rooting habit. A soil type is really the
collective expression of many physical, chemical, and biologi-
cal properties of the whole soil profile, surface soil, subsoil
and substratum. Though we can describe, measure and dis-
cuss many soil properties individually, it must be remembered
that an undertaking of their interrelationship is most im-
"Now, what are the soil properties to be considered in
selecting a suitable soil for tung trees? First let us consider
soil texture. The texture of a soil is defined as the relative
proportion of the various size groups of the individual soil
grains. The various-sized particles have been classified into
three main groups, namely, sand, silt and clay, and these
groups are further subdivided; for example, sand may be
coarse, medium, fine, or very fine. Usually a soil contains a
mixture of all these various groups with one or more pre-
dominating to give the texture name. Loam is the name
given to a class of soil that has about half sand and the
DEPARTMENT OF AGRICULTURE 19
remaining half a mixture of silt and clay. A sandy loam as
intermediate between a sand and a loam. A soil designated
as sand contains less than 10 per cent silt and clay. A soil
containing more than 30 per cent clay is called a clay and if
it has more than 50 per cent sand together with more than
30 per cent clay it is a sandy loam. Many of the subsoils of
the red and yellow soil group in the tung belt outside of the
Florida peninsula are a sandy clay or a sandy clay loam.
"Texture is determined in a practical way in the field
by the feel of the soil and with some practice one can make
a fair estimate of the proportion of the various sized par-
ticles present. If the soil feels very sandy it probably would
be classified as sand. If it is sandy and yet has some body
to it, which makes it hold together when slightly moist,
then it would be a loamy sand or sandy loam. If the soil is
sticky when wet but contains quite a little sand, chances are
it is a sandy clay. There are, of course, laboratory methods
for more accurate determinations which can be checked
against the field observations.
"Soil texture is of great importance because it is an indi-
cator of the water and nutrient holding capacity of the soil
as well as aeration and drainage. Therefore, a knowledge
of this property would be of great help in evaluating a soil.
And this is a soil property over which man has little control.
He has to take it as it is without much hope of being able
to modify it without enormous expense.
"What kind of texture should one look for in selecting a
soil for tung? The most desirable texture of the surface
soil should be in between the clays and the sands, taking
into consideration the effective use of cultural implements
as well as moisture and nutrient storage. If this texture is
unavailable, it is better if the surface soil be on the sandy
side rather than clay, especially if the subsoil contains suf-
ficient clay. Most surface soils in the tung belt are satis-
factory from the standpoint of texture of the surface even
though they are on the sandy side. A sandy surface can be
compensated for by a heavier textured subsoil, which occurs
in most soils of the Southeast. Soils like the Susquehanna
clay are undesirable because of the too-heavy texture of the
surface which makes the use of cultural implements difficult
and is an unfavorable environment for root growth.
20 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
"The texture of the subsoil is probably more important
than the surface as regards the tung tree or any other
orchard tree. Most of the permanent roots are in the subsoil
and therefore it must be a permeable medium and yet have
adequate water- and nutrient-holding capacity. The subsoils
of Orangeburg or Ruston and related sandy loams, which are
common tung belt soils, are excellent examples of soils that
are favorable to extensive root development, are well drained
and aerated, and yet provide an adequate reserve for moisture
and plant nutrients. They have a moisture-holding capacity
in the neighborhood of 20 per cent and a base-holding capac-
ity of about 10 milli-equivalents per 100 grams.*
"On the other hand, in some areas tung trees are being
planted on deep sandy soils as Norfolk and related sands
which, though well-drained and aerated and easily penetrated
by roots, have a very low reserve capacity. The moisture-
holding capacity of the subsoils of this type is about two or
three per cent and the nutrient-holding capacity is less than
two milli-equivalents. This means that the reserve supply
of water and plant nutrients can never be at a high level.
During a dry season trees on this type of soil are more likely
to suffer from a lack of moisture than those on soils of a
higher moisture-holding capacity. But perhaps still more
important is the low capacity of these sandy soils for retain-
ing applied fertilizers, especially bases such as calcium, mag-
nesium and potassium which are only weakly absorbed, and
therefore are readily leached from the soils. It is possible to
produce tung on these soils but only at a relatively high cost.
In other words, they have a low efficiency of production.
Incidentally, we have found that these well-drained deep
sandy soils have a low organic matter content, generally
about 1 per cent.
"There are many soils in the tung belt that have a mantle
of sand several feet deep with an underlying layer of heavier
The moisture-holding capacity of a soil refers to the amount of moisture
a soil can hold after the excess water has drained off. The moisture-holding
capacity of the soils of the tung belt range from less than 1 per cent for some
sands to more than 25 per cent for heavier soils.
The base-holding or exchange capacity of a soil refers to the maximum
amount of such bases as calcium, magnesium and potassium that a soil is able
to hold in reserve against the leaching action of rain. The higher the exchange
capacity the better able is the soil to retain such plant nutrients. The base-
exchange capacity of soils in the tung belt range from less than 1 milli-equivalent
for some sands to 10 to 12 milli-equivalents or more for the heavier-textured soils.
DEPARTMENT OF AGRICULTURE
texture. We do not yet know definitely just how close to the
surface this heavier layer should be to provide more favorable
conditions for growth of the tung tree than will the deep
sands. Observations on several orchards in Florida indicate
that if a sandy clay layer is within five or six feet of the
surface, tree growth is markedly better than on the sands
that are eight feet or more in depth. This past season on
our soil type experimental plots the yield of the trees on the
deep sands averaged only half as much as from those of the
same age and under the same management, but on sands
underlain at from two to five feet by a reddish brown sandy
clay layer. Apparently this underlying stratum provides
enough water and nutrient storage so that the deep roots
may obtain sufficient moisture and nutrients to supply a large
portion of the tree's requirements.
"Certain kinds of clay subsoils as exemplified by the Sus-
quehanna and related clays are undesirable. Though they
have a very high water-holding capacity and nutrient stor-
age, they are penetrated with difficulty by plant roots. They
are sticky and plastic when wet and hard when dry, providing
poor conditions for root development. These heavy textured,
poorly drained soils are characterized by a mottled color of
light gray, yellow, brown, and sometimes red, especially in
"Here again we do not as yet know definitely where to
draw the line between a suitable and unsuitable tung soil,
but we can recognize certain undesirable conditions. Our
observations of tung orchards on such soils as Susquehanna
sandy loam or Bladen sandy loam in which soils the mottled
plastic clay is near the surface, indicate that tung trees
cannot be successfully grown on these soils.
"Not all sandy soils are excessively well drained. In the
lower flatwoods of level topography there are large areas of
fairly deep sands having a water table close to the surface.
This is due to the general high-water table of the area.
Usually a heavy gray mottled clay layer is encountered at a
depth of six feet or less. Due to the standing high-water
table for most of the year, soils of this type are definitely
unsuited for tung trees. These sands can be recognized by
the light gray color usually mottled with yellow and brown
in the subsoil. Often the surface is very high in organic
22 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
matter but the color of the surface and the subsoil gives it
away as an undesirable, poorly drained soil.
"As a general rule the sandy textured soils are very por-
ous. Under certain conditions, however, particularly in the
presence of a high-water table, the sands in the lower layers
may gradually become compacted and cemented by a small
amount of very fine particles, most commonly iron and alumi-
num oxide, silica and organic matter. The presence of a ce-
mented or hardpan layer is very undesirable. Such a layer
is largely impermeable to plant roots and impedes drainages.
This condition is associated with a high acidity and often
with toxic substances.
"Subsoils having a predominantly silty texture and occu-
pying level areas frequently develop a compacted or cemented
subsoil layer. The Pheba fine sandy loam and sandy loam
and related soils, which are common types in Mississippi
and Louisiana, are examples of this type of development.
The degree of cementation and the depth at which it occurs
vary considerably. A strongly cemented layer within two
feet of the surface appears to be very detrimental to the
normal growth of tung. Roots have difficulty in penetrating
the hard layer and in wet seasons the soil above may be tem-
porarily waterlogged and the lower roots may be killed. Then,
when the soil dries out, the surface roots may not be able to
function normally due to lack of moisture. The soil just
above the cemented layer as well as the compacted layer
itself is generally very light gray in color, somewhat mottled
with light yellow and brown and occasionally red. The com-
pacted layer may be 12 inches or more in thickness and is
easily recognized when one attempts to dig a hole in this soil.
"In the foregoing discussion considerable emphasis has
been placed on soil texture and the various conditions asso-
ciated with this important soil property. As mentioned in
the foregoing, it is difficult to control soil characteristics
that depend on the texture of the soil. Although heavily
waterlogged clays can be drained, hardpans can be dynamited
and large amounts of fertilizers can be placed on the easily-
leached sands, all these measures involve expenditures much
too large for the profitable production of tung trees. It
might be mentioned that young trees may do fairly well on
some of these soils-their moisture and nutrient requirements
DEPARTMENT OF AGRICULTURE
are not large and the root system is not extensive. But as
the trees attain bearing age and their demands for nutrients
and moisture become much larger, the harmful effects of
either a very light sandy or a heavy plastic clay, or the
presence of a cemented hardpan within two feet of the surface
begin to show.
"Color is an important criterion in selecting a soil for tung,
not that the color is in itself of any value, but rather as an
indicator of several important characteristics. A dark color
of the surface indicates the presence of some organic matter
and, of course, the more organic matter the better. However,
here in the tung belt, if the surface soil is too dark, that is,
black or almost black, then one should be on guard. Organic
matter generally accumulates in this region in greatest
amounts in wet, poorly drained situations. A very light
gray mottled subsoil underneath a black surface soil would
be too wet for tung. In the tung belt the normal well-drained
and well-aerated soils of high storage capacity for moisture
and nutrients have a gray, brownish gray, grayish brown, or
brown surface soil. The deep sandy soils usually have a very
light gray surface and the poorly drained types have either
a dark or black or pale gray surface. If the surface is red
or yellow, it indicates that the original surface soil has prob-
ably been eroded exposing the red or yellow subsoil.
"In the subsoil a uniform bright color free of streakings
or mottlings is most desirable. A mottled condition in the
upper subsoil, especially the dull gray, brown and yellow
mottlings, indicates poor drainage and aeration for at least
a part of the year and should be avoided. Mottlings and
streaking due to poor drainage should not be confused with
mottled condition of the substratum or parent material of
well-drained soils like the Ruston and Orangeburg sandy
loams. In the latter instance, the mottling is inherent in
the parent material as a result of the manner in which the
material was originally deposited and is not of much sig-
"The topography of the soil is an important factor to be
considered. In general, gently rolling land at elevations
higher than much of the surrounding area is most desirable.
Naturally, river bottoms, low terraces, and valley floors are
to be avoided, especially with a tree like the tung which is
24 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
so sensitive to spring frost. Flat land, either on a ridgetop
or lower ground, is generally associated with poor drainage
and is therefore undesirable. Steeply sloping land though
usually well drained and aerated is easily eroded and difficult
to cultivate and ordinarily should be avoided. It should be
pointed out that sloping land is not always well drained. The
surface drainage may be good, but the presence of claypan
or hardpan or other impervious strata close to the surface
may create very unfavorable conditions for the growth of
trees even on a considerable slope.
"The fertility level of a soil should be high enough to meet
the needs of the tree. This is a soil characteristic which can
be rather easily controlled and an infertile soil may not neces-
sarily be unsuited to tung provided other soil conditions such
as desirable textural properties are favorable. For example,
a low potash content can be easily remedied by the applica-
tion of potash fertilizer at a reasonable cost if the soil is of a
type that does not leach readily. On the other hand, a high
fertility level may not necessarily mean that the soil is pro-
ductive. Some poorly drained soils have a high nutrient con-
tent but are unproductive because of the inability of the roots
to grow and develop properly and utilize the available nu-
trients. In general, the soils of the tung belt are deficient
in most plant nutrients and some fertilizer must be used for
successful fruit production. For most soils a moderate amount
of commonly mixed fertilizer should be satisfactory. On
many soils we now recognize that in addition to the regular
mixed fertilizer a small application of micro elements such
as zinc and manganese and possibly others, is essential.
"In order to meet the fundamental requirements for
the successful production of tung trees, a soil should
have favorable topography on the higher elevations; it
should be well aerated and drained and have a high mois-
ture and nutrient capacity; it should be easily penetrated by
plant roots and have an adequate nutrient level. Those soil
properties which cannot be controlled without tremendous
costs should receive most attention in selecting an orchard
site. Heavy clays, deep sands, soils with a hardpan close to
the surface, soils with a high-water table and gray mottled
soils-all of these fail to meet the essential requirements for
success in growing tung trees. Of the soils in the tung belt,
Orangeburg, Ruston, Norfolk, Red Bay, Greenville, Tifton
DEPARTMENT OF AGRICULTURE 25
and related sandy loams and fine loams are undoubtedly the
most desirable soils, while the deep Norfolk sands, Susque-
hanna and Bladen clay soils of Leon, Caddo, Coxville, and re-
lated series cannot be expected to grow tung trees success-
Best Locations for Tung Trees
Tung culture must be handled with intelligence. Experi-
enced growers are few because of the newness of the in-
dustry. Comparatively few trees now growing for commercial
purposes have not reached maturity hence Southern farmers
are learning by experience as their trees grow.
The selection of suitable land is of first importance in
tung culture. With the wealth of available printed matter
covering this subject, there is no excuse for planting a tung
grove on land that is obviously not fitted for this purpose.
Other than killing frost, most of the dangers which beset
tung farmers can be obviated by the farmer's knowledge of
soils that are suited to tung culture.
It has been suggested by R. D. Dickey, of the Florida
Experiment Station's horticultural department, that a farmer
contemplating the growing of tung trees should first of all
obtain Government temperature records for a period of sev-
eral years on the place he expects to set out in tung trees,
or else be sure that his land is higher than the surrounding
terrain, thus giving the cold air a chance to drift away from
the grove to the lower land levels.
One grove, located near Gainesville, for instance, was cited
as an example of bad location selection by J. Francis Cooper,
of the Florida Agricultural Extension Service, in an article
published in the Florida Grower of September 1940. This
grove has suffered periodically for several seasons and lost
all of its crop three out of four years. Another grove, only
15 miles away, suffered smaller losses from cold, a difference
attributed to the elevation of the latter, this one being 55
feet higher above sea level than the other. Air drainage is
important as well as soil drainage.
The planting of tung trees has been suggested as a solu-
tion to many of the difficult agricultural problems of the
South. It is contended that the addition of this new indus-
trial crop would assist in diversifying agricultural activity
and would bring a more balanced economy to the region.
We know now that timber exploitations in Florida have
far exceeded replacement by reforestation. The large and
increasing acreage of cut-over timberland represents, at
DEPARTMENT OF AGRICULTURE
present, a considerable economic loss to the State. Therefore,
the problem of a profitable utilization of these waste lands
has been of material concern to lumber companies and other
large owners of such land.
Tung nuts have been visualized as a potential crop on
much of this land. If the tung tree satisfactorily solves this
problem, benefits will accrue not only to the property owners,
workers, and all classes deriving income or sustenance from
the land, but to county and State treasuries, as well, in the
form of increased taxes. Much of Florida's cut-over land has
been on the delinquent tax list for many years and is a dead
It is expected that war demand for tung oil will soon send
farmers scurrying into some of these waste places to set out
acreage in tung trees. Here lies a grave danger. If the
selection of a tung site is made wisely, it may lead on to
fortune; if unwisely made, the selection may lead only to
disaster. There will always be a strong market for tung oil
and its successful cultivation will mean a safe cash market,
even in the peace that will follow the present war.
Extensive planting of tung trees may lead to the develop-
ment of an extensive milling industry, a movement in keep-
ing with the trend toward industrialization now quite evident
throughout the South. Since tung oil, turpentine, and rosin
are essential raw materials in paint and varnish manufacture,
leaders in the paint industry, as well as tung tree planters,
have visualized the commercial production of tung oil, in
conjunction with the already well-developed naval stores in-
dustry, as an incentive to the extension of paint and varnish
manufacture in that region.
Forestry authorities have recommended the growth of the
tung tree in hilly or rolling areas, where its long tap roots
would serve as a protection against excessive erosion and
resultant exhaustion of the soil. Such plantings may assist
farmers in the more economic use of their uncultivated land,
since tung trees grow satisfactorily on hillsides and on irregu-
lar plots of ground which may be difficult to utilize for
general farming. In some localities a few plantings have
been made along railroad tracks, highways, and edges of
fields, so that the trees, in addition to yielding nut crops,
28 TUNG OIL--AN ESSENTIAL DEFENSE INDUSTRY
may be used instead of posts for stringing wire fencing.
Having a beautiful bloom, the tung tree adds greatly to scenic
The development of tung oil production in Florida into a
generally profitable, fundamentally sound and important in-
dustry, covers a range of possibilities, with success or failure
depending largely upon the intelligent employment of defi-
nite tung knowledge, and the application of principles neces-
sary to the success of any business.
It appears, however, that advantages for profitable cul-
ture would seem to be with the large grower, because of
economy in maintenance, purchasing, and usually the fact
that the large grower has sufficient capital to see him
through to successful production. The small grower, with
limited income, has certain advantages in his favor, however.
The farmer with limited income, as suggested, might find
tung culture an opportunity for increased diversification and
profit, provided, of course, his land and its location is adapt-
able to tung oil production.
With proper regard for the land, he may intercrop among
his tung plantings, thus reducing the expense of the growing
tree. In localities with a number of small groves, the growers
can probably band together advantageously for co-operative
supervision, maintenance, purchasing, and eventually mar-
keting, thus following an already marked trend in co-operative
agriculture throughout the State of Florida.
Commissioner Nathan Mayo of the State of Florida De-
partment of Agriculture has taken pains to warn prospective
tung growers against certain pitfalls if they would become
successful growers. He suggests that more and more farmers
should grow tung trees, but he cautions them to regard the
fundamental requirements for successful tung culture: suit-
able soil, proper drainage, favorable climate, proper planting
with the right kind of seedlings, and the right fertilization
Preparing Land for Tung Trees
After a tract of land has been carefully selected, it must
be prepared for the planting of tung trees with equal care.
As Mr. Adderley states in American Tung Tree, "Owing to
the rapid growth and heavy fruiting habits, the tung tree
makes great demand upon the soil. What is taken from the
soil must be restored in excess, if soil fertility is to be
maintained and increased crop production is expected. Tung
trees cannot be grown to commercial advantage without
The State of Florida Department of Agriculture stresses
the fact that because of the wide diversification of soils in
character and fertility, a definite knowledge of the chemical
requirements of land is necessary for the correct fertilization
of a tung grove.
Methods of preparing land for tung trees do not differ
materially from the methods of ordinary farming. New land
should be cleared of all brush and stumps. If the land has
been previously cultivated, it should be cover-cropped the
season before the trees are to be planted, unless such land
has been well maintained in humus and general fertility. This
will increase both the humus and nitrogen content of the soil,
thus affording a good start. Crotalaria, cowpeas, velvet
beans, beggarweed, are all good cover crops and are usually
planted in February or March. Such crops are generally
turned under in October or November. The land to be planted
should be thoroughly ploughed and then disced or harrowed
to compact the soil. On some types of Florida soil there is a
controversial point as to whether the cover crop should be
turned under at all, as the fertilizing value might leach away
during the winter months. This may be corrected by growing
winter and summer cover crops.
Speaking of the proper fertilization of Florida land for
tung tree culture, Mr. Adderley states in American Tung
"Soils are often deficient in one or more of the principal
elements of available nutrition; namely, nitrogen, phosphorus
and potassium. The amount of tree growth and fruit yields
produced are largely dependent upon these three principal
30 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
elements in proper balance and proportion. There are many
other mineral elements which the tree requires, but these
three are required in greater quantities.
"The growth of the tung tree and the fruit yields produced
will give some indication of the fertility or lack of fertility
in the soil. This indication, however, cannot determine the
element or elements which may be deficient or absent. It is
advisable to have the soil analyzed at regular intervals, in
order to definitely determine the amount of available plant
food and its character. Fertilization by guess work invari-
ably involves needless waste and expense, and usually does
not serve the best needs of the tree. A soil analysis will
deetrmine to a degree the elements of nutrition that are
lacking and permit their most economical replacement.
"Good results have been obtained from the use of mix-
tures of commercial fertilizer containing nitrogen, phos-
phoric acid, and potash. A formula analyzing 5 per cent
nitrogen, 7 per cent phosphoric acid, and 2 per cent potash
will generally give good results during the first two or three
years. It is desirable to have the major supply of nitrogen
from organic sources.
"When the tung tree reaches bearing age, it requires an
increased percentage of phosphoric acid and potash in the
fertilizer mixture. The following formula is recommended
for a 4- or 5-year-old tree: 4 per cent nitrogen, 8 per cent
phosphoric acid and 4 per cent potash. Seven- and 8-year-old
trees will require 5 per cent nitrogen, 8 per cent phosphoric
acid and 6 per cent potash.
"Tung trees should be given two applications of fertilizer
each year. The tree has two periods of intense activity each
season. The first period begins with the growing season in
early spring. The tree then blossoms, foliates, and sets its
fruit. During midsummer, there is an intervening period,
which occurs usually during the month of July. The tree
then sends out its new growth, sets its buds for the following
year, and fills its fruit.
"Fertilizers are applied to the best advantage at the be-
ginning of each of these active periods. The first application
of fertilizer should be made at the time of the first cultivation
at the beginning of the growing season. The second applica-
DEPARTMENT OF AGRICULTURE
tion of fertilizer is made during the rest period in the month
of July, which is just in advance of the second period of
"Unless the soil is exceedingly rich, it is considered good
practice to give the newly planted trees an application of
from one-half pound to one pound of fertilizer soon after
transplanting. From one to two pounds per tree may be
given in midsummer. At the beginning of the second year
of growth, two pounds per tree may be used for each appli-
cation and from two pounds to three pounds per tree may
be used at each application during the third year. Beginning
with the fourth year, apply three pounds or four pounds per
tree at each application.
"Cover-cropping is highly recommended to provide and
maintain an adequate supply of humus and nitrogen in the
soil. A good legume, such as crotalaria, beggarweed, cow-
peas, velvet or soybeans will serve this purpose. Crotalaria
is recommended because of its abundant growth and high
nitrogen-producing value. Crotalaria strict is the best
growing variety and will reseed itself from year to year.
Stricta is good cattle forage.
"The press cake, or residue remaining after the extraction
of tung oil from the tung seed has been found to have a high
value as a fertilizer. It has a relatively rich nitrogen content
and in addition contains a small amount of phosproric acid
and potash. By the use of press cake as a fertilizer, together
with cover-cropping, it will be possible to maintain a near
balance in soil fertility by additions of phosphorus and
potash. In this way, a lower cost of fertilization may be
"All animal manures are good fertilizers and should be
employed whenever available. Animal manures contain a
high ammonia nitrogen content which is quickly converted to
nitrate and is then available for the use of the tung tree.
Chicken manure has been found to give most excellent results.
This form of fertilizer, in addition to the usual elements
found in other fertilizers, has a zinc content. This zinc
element contributes largely to the health of the tung tree
and to the availability of other nutritive elements.
32 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
"Too rapid growth upon the part of the young tree is
inadvisable. It results in long, gangling branches which are
usually brittle and susceptible to wind damage. Such trees
are often unable to support the weight of a normal nut crop.
In such cases it is advisable to add potash in some available
form. This will slow up the tree growth and harden the
wood," for better fruiting.
Planting and Maintenance
Because of the wide variation of land values suited to
tung culture, as well as variations in clearing costs, due to
the types of vegetation growing on the lands, it is difficult to
arrive at a precise cost range of planting and maintenance.
Always bearing in mind that large acreages can be produced
and maintained at a lower proportionate cost than small
plantings, the first year's expenses may be divided approxi-
mately as follows:
Nursery Stock: $15 to $50 per acre.
Clearing: 8 to 40 per acre.
Plowing, Breaking: 2.50 to 5 per acre.
Planting: 4 to 6.50 per acre.
Cultivation: 5 to 10 per acre.
Fertilizing: 4 to 6 per acre.
After the first year the fertilizer costs gradually increase,
but as the trees grow, cultivation costs in turn gradually
decrease. Since about 10 pounds of high grade fertilizer
should be the maximum quantity applied to mature trees,
this expense will be but the cost of 700 to 1,200 pounds per
acre, plus the low cost of application. From $25 to $30 per
acre should cover fertilizer and labor costs on a mature
Because of the newness of the industry, present tung
plantings consist almost entirely of seedling stock. Such
stock, thoroughly tested for proficiency, can be obtained at
reputable nurseries. Seedlings are usually transplanted to
the field after a season's growth. The nursery method ap-
parently is preferable to planting seeds directly in the field
because of the cost of cultivation and the reduced opportu-
nity offered for the elimination of undesirable seedlings.
Only the most vigorous seedlings-those showing a well
developed top and root system-should be selected. As de-
scribed, the production qualities of a tung tree in most cases
run true to those of its parent. However, all trees should
be carefully checked each year and when one fails to meet
satisfactory standards, it should be eliminated.
It is only during the dormant period of December, Janu-
ary, and February, when the trees are entirely defoliated,
34 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
that seedlings should be set out. The root system should be
well protected and kept moistened until set out. If the trees
cannot be planted shortly after received, they should be
"heeled in" with plenty of moist earth for coverage. Laying
out the land depends upon the number of trees to be set to
the acre. At the time of transplanting, the trees should be
cut back within 6 to 10 inches above the ground to over-
balance the root system against the upper structure, thus
providing vigorous growth and greater uniformity in the
The tung tree has a very shallow rooting habit of many
of its feeders, therefore its cultivation should be done with
care. As soon as the young tree has started to grow, it is
well to cultivate the ground for a distance of four to six feet
on each side of the tree, hoeing around the tree to keep the
area clean and without risking injury to the trunk or roots.
Cultivation should be sufficiently thorough to keep down
weeds and grass and at the same time shallow enough to
leave the root system undisturbed.
The fruiting habit as distinguished by the "single" and
"cluster" type has been found to have a decided effect upon
yield. However, it is cautioned by Dickey and Reuther, not
all trees which would be classified as cluster type are de-
sirable, nor can it be said that all single type trees are un-
desirable. In general, though, it is the best character found
so far upon which to base the selection of a superior strain.
Data supplied by Mowry and Newell and others substantiate
this. Of the 34 highest yielding trees in the block, 24 were
of the cluster type and 10 of the single type. Twenty-three
of the 34 lowest yielding trees in the block were of the single
type and 11 of the cluster type.
To determine whether or not size can be used as an index
to the ability of a tung tree to yield, the low- and high-
yielding trees were carefully compared. It was found that
there was no correlation between size as evidenced by cross-
sectional area of the trunk and the ability of a tung tree to
yield. It is therefore evident that size alone cannot be used
as an index for ascertaining the high- or low-producing trees
in a planting or in the selection of desirable strains for future
DEPARTMENT OF AGRICULTURE
All trees in this block were carefully studied to determine
if yield could be correlated with any particular tree conforma-
tion. Some of the factors considered were type of branching
and shape of head (whether round or pyramidal, compact or
loose, upright or drooping). No particular conformation was
found to be correlated with yields.
Careful study of the flowering habit has brought several
interesting facts to light. For instance, it was shown that
there is a large and consistent difference in the volume of
bloom produced by many trees in this block. So profuse was
the flowering of some trees that they appeared to be a solid
mass of bloom, while other trees produced relatively little
bloom. Every graduation between these two types was found.
A careful check showed that there was no consistent correla-
tion between volume of flower production and yields that
could be used as an index for the selection of high-yielding
trees. The number of normal pistilate flowers produced was
the critical factor affecting the yield. From this study,
Dickey and Reuther thus concluded: "It seems probable in
view of the data herein considered that this is a factor in-
herent in the genetic constitution of the tree rather than the
result of condition of vigor of the tree. It is not intended to
imply, however, that the differentiation of the amount of
flower primordia is not influenced by the condition of tree
vigor. As yet no direct evidence is at hand indicating that
the condition of vigor of tung trees can markedly influence
the relative proportions of staminate and pistillate flowers
A question often asked in tung tree culture concerns the
height of branching. Observations made and records kept
by Rolfe Buckley, of the Alachua Tung Oil Company, and re-
produced in Bulletin 343, show that a large percentage of the
trees that branch low in the nursery, "low-headed" trees,
when planted in the field cut back to from 6 to 8 inches above
the ground and subsequently trained to a single trunk, will
again branch in this manner, while "high-headed" trees
treated in the same manner will again branch as high-headed
Seed from a single parent tree produced both high- and
low-branching trees in the nursery. However, the ratio of
each type produced varied, depending upon the parent tree.
36 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
One tree, high-headed, had approximately 98 per cent of its
seedlings branching as high-headed trees, while another
tree, low-headed, had approximately 95 per cent of its seed-
lings branching as low-headed trees. The data presented in-
dicated that the height of branching and its subsequent effect
upon the height of head is a definite genetical character.
When a high- or low-headed type of tree does not make
sufficient growth to branch during its first year in the field,
often an undesirable condition arises. As this type of tree
begins growth the following year, often the central leader
is suppressed and makes no further growth, and several
branches are put out at approximately the same level on the
tunk which produces a tree commonly spoken of as a "cart-
wheel." This forms a very weak crotch, with the result that,
when such a tree begins to fruit, almost invariably it is split
to the ground. To prevent such a condition, those trees which
have failed to branch should be cut to from 6 to 8 inches
above the ground. The resulting growth the following year
should be strong enough so that branching takes place as
Because irregularities are frequent when production traits
are generally transmitted from the parent tree to seedlings,
growers have shown increased interest in asexual methods
of propagation, or what is known as budding or grafting.
According to the Florida Agricultural Experiment Station,
the absolute value of these methods has not been definitely
established, but many growers are experimenting and some
predict that future propagation of the tung tree in this coun-
try will resolve entirely into a matter of budding.
Except for the removal of dead, broken, or interfering
branches, pruning of older trees is of negligible advantage
and tends to reduce the number of fruiting trees, with a
consequent reduction in yield. Development in tree culture,
however, is largely dependent upon a certain amount of spe-
cialized pruning in the tree's initial period of growth.
Bronzing is a physiological disorder which seriously af-
fects tung trees on certain soils and in certain localities. The
name is suggested by the bronze coloring of the leaves shortly
after the affliction has passed out of its initial stage. With-
out proper treatment, the tree becomes stunted and ultimately
dies. Experiments carried on by the Florida Agricultural
DEPARTMENT OF AGRICULTURE
Experiment Station since 1931 have more or less determined
this condition to be the result of certain chemical malnutri-
tion which, in most cases, can be corrected in time.
Frenching is another and quite different disorder to
bronzing and has been found to occur in varying degree over
a widespread area. It is a type of partial chlorosis and
necrosis affecting tung tree foliage suggesting the name
frenching. Observations made in a preliminary survey in the
spring of 1937 indicated that between 5 and 10 per cent of
commercial tung plantings evidenced symptoms of this dis-
order to some extent. Experiments led to the issuance, in
December 1937, of a special bulletin, No. 318, by the Florida
Agricultural Experiment Station.
The grower of tung trees must realize that during the
first three years of the tree's life in the groves there will be
some mortality. The number of trees lost will depend upon
climatic conditions, care at time of planting, and supervision
of the grove. In one Florida grove the figures ran from 3 to
22 per cent. A fair average might be 8 per cent.
Harvesting and Marketing
The first tung crushing plant for the extraction of tung
oil in Florida was erected by the Alachua Tung Oil Company,
and during February 1932 the first tank car of the State's-
produced tung oil moved from Gainesville.
an annual production of approximately 4,000,000 pounds,
which was increased the following year to 5,000,000 pounds.
Florida produces only a small fraction of the needed supply,
as the United States in peacetime annually consumes about
130,000,000 pounds. Because the Nation is now at war and
tung oil is essential in so many war industries, it is difficult
to predict the potential needs of Uncle Sam for this vital
product for the duration of the war. Thus a supermarket has
been created for tung oil, largely because of its waterproofing
qualities, which can be filled only by the earnest, intelligent
effort of growers.
Writing for the Florida Grower of May 1939, B. F. Wil-
liamson, tung expert for a score of years, said:
"When the first recorded shipment of wood oil from China
was made in 1869, its value was not appreciated at first,
principally because of the fact that the various gums avail-
able at this time were so abundant and cheap that there was
no apparent need for tung oil. But these gums were being
rapidly worked out and as a result a closer examination was
made. It was found that varnishes properly made from tung
oil were much more resistant, particularly to water, than the
older and more expensive varnishes made with linseed oil
and fossil gum.
"Since the beginning of the present century the use of
tung oil has become general in paint and varnish manufacture,
with a consequent market improvement in the quality of these
products. One reason why tung oil is so valuable is that
when heated to 2500 Centigrade it changes in a very few
minutes from an oil to a gum. Once this gum is set, it forms
an elastic film that is very durable, insoluble in practically
all solvents, and highly resistant to water as well as oils.
"American tung oil is far superior to the Chinese product.
It is lighter in color, practically neutral and makes a clearer,
more uniform, finished product."
DEPARTMENT OF AGRICULTURE 39
Harvesting tung nuts is a simple, inexpensive operation.
The nuts are allowed to ripen on the tree and fall to the
ground, where they are left to dry. They are then collected
in sacks and transported to the tung oil mill nearest the
grove. Most tung mills operate with a disc machine that re-
moves the hulls from the nuts, and a screw press that extracts
the oil. When processed in this manner, a ton of fruit pro-
duces about 350 pounds of tung oil, worth 20 cents a pound,
350 pounds of meal worth $15 a ton as a fertilizer, and
slightly over half a ton of worthless hulls.
The fruits mature and fall to the ground during the latter
part of October and the early part of November. Gathering
them by hand is largely a matter of convenience, except that
if they are allowed to lie on the ground after the trees shed
their leaves, the operation of recovery from the leaves is
difficult and more expensive.
The whole fruits should be stored where they are com-
pletely protected from moisture until they are thoroughly dry.
Hulls should be removed because of possible damage to the
pellicle or seed coating and a consequent decrease in the
quantity and price of the oil. If the nuts are stored in sacks,
the sacks should be arranged to permit air circulation. When
stored in bulk, they should be placed on a dry floor with
air circulation beneath and turned with a shovel once or
twice a day. The nuts may be marketed any time within six
months after they are dry, thus affording the grower a pos-
sible opportunity to dispose of his crop at advantageous
40 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
Oil Extraction Methods
For thousands of years Chinese workers have carried tung
fruit on their backs from the groves to the place where the
oil has been extracted. The crude Chinese method of ex-
traction resulted in a product that varied in degree of purity
and quality. It is said that the American method of ex-
tracting the oil results in a saving great enough, over the
Chinese method, to more than pay the cost of the extracting
machinery and for the extracting operation.
Before pressing, the oil in the seed is almost colorless,
the depth of color in the expressed oil depending in part on
the method used in extraction. American oil has a very light
amber or straw color, and a very low acid content. Both
chemical and mixing tests have demonstrated the superiority
of the American product. Tung oil yield is about one-third by
weight from air-dried seed and about one-fifth by weight
from air-dried whole fruits.
The two methods of oil extraction are by volatile solvent,
and by screw press, or expeller. Comparative tests have
proved that the latter is best from standpoints of both
economy and efficiency. This is the method pursued at
and within the Gainesville area. The oil operation is con-
tinuous and almost wholly mechanical. Air-dried whole
fruits are husked by a combined huller-separator. The seeds
are then conveyed to a grinder which converts them into a
coarse meal. This meal is in turn fed into the expeller, which
extracts the oil by pressure. Further treatment of the oil,
other than filtering, is not required and it is soon ready for
storage or use.
The pomace or seed cake, which is left when the oil is
extracted, contains about 6 per cent of ammonia and com-
pares favorably in analysis with castor pomace, a material
valuable as a fertilizer. The hulls can be used to advantage
as a fertilizer and for mulching purposes.
DEPARTMENT OF AGRICULTURE
Hazards for Tung Culture
Because of the newness of the tung industry and the
interval of time that must elapse before the tung trees now
growing can reach maturity, it is wise for the inexperienced
grower to make a thorough study of tung culture before
planting his seedlings. Many industrialists and Federal and
State agencies, that wish to see the tung oil industry succeed
in this country, are endeavoring to warn potential tung grow-
ers not to plant any trees before acquiring the fundamental
knowledge, now available, which is vital to the successful
development of tung culture in the United States.
Failures of the past have been mainly due to inexperi-
enced persons entering a field they did not understand. Nor
could they until scientists and technicians had paved the way
by actual experimentation. Today there should be no such
cause for failure, because chemists and technicians are able
to tell prospective tung growers how to plant so that their
trees will yield a profitable cash crop, and, at the same time,
contribute a valuable agricultural product to the Nation's
economy. A 1935 Farm Credit Administration report revealed
that 2,045 acres of tung trees had been abandoned. This is
sufficient reason to show that important hazards face the
persons who enter the business of producing tung oil.
During the brief period of its existence, the tung industry
in Florida, as elsewhere throughout the tung belt, has en-
countered many of the same difficulties as those experienced
in the early days of the citrus industry. Unscrupulous real
estate promoters took advantage of a promising new in-
dustry and by extravagant statements induced many inex-
perienced farmers to plant orange groves, without first ob-
taining knowledge of citrus culture. Certain promoters cast
truth to the wind, and pictured sudden wealth for all who
would plant tung trees.
With the best selection, care, and intelligent husbandry,
a commercially profitable crop cannot be produced until at
least the fourth year after the trees are planted. Records show
that in the average instance any production in the fourth
year serves only to counteract the expense for that year.
"The planting and successful production of tung oil," says
Mr. Adderley in American Tung Tree, "is a horticultural un-
42 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
dertaking which requires the exercise of a high degree of
intelligence. There have been many failures and disappoint-
ments in the past. Failures are always present in new in-
dustries where a trial and error method is necessary over a
period of many years to determine and establish proper
methods and practice. In spite of the bitter experiences of
the past, many fallacies still continue to persist. The great-
est of all horticultural heresies is the theory that the tung
tree, being originally a wild tree, will grow and produce
profitable crops with little or no cultivation or fertilization.
"Next to the fallacious theory of profitable crops from
cultivated or unfertilized groves, more failures have resulted
from the fact that the prospective grower has been unable to
finance and cultivate his grove through the term of years
required to reach commercial production. The result is an
abandoned grove with dwarfed and stunted trees which can-
not be resurrected. Many such groves might have been car-
ried to the successful production stage, except for the fact
that the planter undertook to plant a greater acreage than he
could properly finance and care for."
It was for the purpose of pointing out to prospective tung
growers the several pitfalls to be avoided in successful tung
culture that the American Tung Oil Corporation was formed.
Financed largely by members of the National Paint, Varnish
and Lacquer Association, Inc., this corporation, as explained
in an editorial published in Tung Oil Culture in June 1937,
entitled "Warning," was organized as an experimental unit,
or field laboratory, to demonstrate the possibilities of grow-
ing tung oil in America, with the object of making this coun-
try less dependent upon foreign sources and of preventing
violent price fluctuations; to develop agricultural information
as to the best methods of growing trees; to act as an experi-
mental and educational unit so that the information obtained
could be disseminated widely in order to encourage larger
and more successful plantings of tung by others, and to make
available to such outside planters a source of selected,
multiple-cluster type seed.
Although the corporation in 1935, realizing that its ex-
perimental groves were not productive, sold its properties and
discontinued field experimental work, the negative lessons
provided by these groves were of great value to planters in
DEPARTMENT OF AGRICULTURE
showing them things they should avoid in establishing suc-
cessful groves. The main object of the corporation's efforts
may be considered to have been successful, however, as plant-
ers in increasing numbers continued to set out groves in ap-
proved fashion, careful to avoid the pitfalls that were pointed
out to them. Other tung oil corporations have been formed
throughout the tung belt.
The "Warning" editorial also contained the following in-
formation: "It has rarely been pointed out in advertisements
that lands may be purchased in certain sections as low as $5
or $10 an acre in the uncleared state. Moreover, it has not
been pointed out that the cost of growing young trees and
transplanting them in grove formation is very low. Such
information obviously should be brought to the attention of
the public so that investors would not be expected to purchase
groves at extremely high speculative prices. Moreover, the
public should be warned that tung trees will not grow on
every type of land, and that it is extremely important that
well-drained land of the right soil characteristics should be
selected. A careful soil survey by an expert should be made.
"Information should also be obtained as to whether sub-
stantial yields of fruit have actually been produced by grove
plantings in the localities under consideration. Even after
the groves are planted, they should receive careful cultivation
and attention if they are to produce good yields of fruit. The
planting of tung trees should be encouraged only in such lo-
calities as are favorable. The more successful results will
doubtless attend the planting of trees in good-sized acreages
under competent management with the requisite corporate or
personal financial arrangements to carry the groves through
to production. Such undertakings should preferably not in-
volve solicitation for subscription to stock or land units."
The "Warning" editorial further points out that "The
planting of small five- or ten-acre groves will probably not
pay unless done individually by farmers who may have small
acreages of land upon which the groves may be planted and
used for chicken runs or similar purposes. The planting of
large tracts of from 100 to 1,000 acres or more would seem to
be necessary if the overhead of carrying the groves through
to production is to be properly distributed in order to make
the venture more profitable.
44 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
"The public should also be warned against statements
which set forth that great profits may be made from tung oil.
Such statements are usually based on theoretical estimates of
fruit yields. Estimates on individual trees rather than upon
groves are apt to be misleading.
"It would appear that tung oil production in America has
become established in certain selected areas and may rapidly
grow, provided every care is exercised to select good land,
to take care of the groves, and to finance the projects on a
logical basis without expecting the general investment to
carry the burden.."
Production of Tung Oil in Florida
Summarizing the development of tung farms in Florida,
a book published by the State of Florida Department of Agri-
culture in July 1938-A Graphic Review of Florida Agricul-
ture-made these statements:
"The first commercial plantings in Florida were made in
1923, and comprised 140 acres. In 1924 the acreage had in-
creased to 300, and the census of 1930 reported 85 farms lo-
cated in 20 counties, with plantings amounting to 300,824
trees of all ages. The 1935 Federal census of agriculture
reported 1,054,511 trees on 174 farms in the State, repre-
senting 13,478 acres; and still more recent unofficial esti-
mates place the present day (1938) acreage at between 17,000
and 19,000 acres. In six Southern States tung trees increased
in number nine-fold in the five years from 1930 to 1935."
The 1939 production figures for Florida, which appeared
in the 1940 Federal census of agriculture, present an inter-
esting picture. Fifty-one Florida farms reported a combined
crop of 1,112,115 pounds of tung nuts. A total of 367 farms
reported acreage planted to tung trees, with 758,935 trees
not of bearing age and 449,829 trees of bearing age.
More than half of the crop, 578,575 pounds, was produced
on 13 farms in Alachua County; over a third, 340,060 pounds,
came from 3 farms in Levy County; and a tenth of the crop,
120,620 pounds, was harvested on 3 farms in Jefferson
County. Thus, only 19 farms located in three counties pro-
duced more than nine-tenths of the 1939 crop.
DEPARTMENT OF AGRICULTURE
A total of 32 other producing farms, scattered through
14 additional counties, had a combined crop of less than
73,000 pounds of tung nuts. And there were 316 tung farms
that produced no crop at all. This unfavorable side of the
picture was not as bad as it seems. Thousands of trees had
not yet reached bearing age, in fact a majority of the trees
in the State were immature. On the other hand, the blossoms
on large numbers of trees were killed by frost, and the im-
proper cultivation and poor location of many trees kept them
from achieving a fruitful maturity.
According to the Florida Times-Union of July 20, 1941,
some 2,000 farmers participated in a profit of $1,000,000 from
the 1940 tung crop of six Southern States-Georgia, Florida,
Alabama, Louisiana, Mississippi, and Texas. This 1940 growth
represented the yield from only 18,000 acres, but was the
largest crop ever harvested in the United States. This paid
the farmers about $55 an acre.
Dr. Wilmon Newell, director of the Agricultural Experi-
ment Station, College of Agriculture, University of Florida,
stated on August 18, 1941: "There were approximately 10,-
000,000 pounds of air-dried tung fruits produced in Florida in
1940, from which 1,600,000 pounds of oil were extracted."
In its issue of July 20, 1941, the Florida Times-Union
reported: "It is estimated that there are 200,000 acres of
tung trees under cultivation in the Southern tung belt. But
as it requires from five to six years for a tree to mature,
the yield from this acreage will not be available until 1946
or 1947. In the meantime, it is estimated that if 100,000
additional acres can be devoted to tung culture, this country
within a few years could produce sufficient tung oil to take
care of its normal needs." That statement was made before
war was declared against the Fascist nations. What the
war will require in tung oil production is quite another matter.
H. W. Bennett, prominent Florida grower of tung oil,
said on September 9, 1941: "Tung oil for northern Florida
is potentially as great an industry as is its citrus to southern
Mr. Bennett blames some of the earlier failures in the
State to bad promotion which hurt the tung industry just as
bad promotion injured the early citrus trade. He sounds a
46 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
note of caution, however, that even under the most favorable
soil and climatic conditions, two hazards are possible. One
is a possible frost on the spring bloom, the other, price. Mr.
Bennett believes that "Every farmer should have ten acres
in tung on suitable land as a cash crop. It has been demon-
strated that under proper conditions he can get two tons of
nuts an acre along the eighth or tenth years. The mills last
season paid $60 to $65 a ton. This was about $120 to $130
In the spring of 1939, Congressman Lex Green of Florida
requested that tung growers be given a Federal subsidy to
encourage the culture of tung trees, but the suggestion was
not looked upon with favor by Secretary of Agriculture Henry
A. Wallace, at the time. Informed persons, however, believe
that the new war situation may result in the adoption of
Congressman Green's suggestion.
One of the early pioneers in the Florida tung oil industry
was the General Tung Oil Corporation, of New York. On
December 31, 1928, Bailey Finley Williamson, president of
the firm, made two important announcements. One was that
his corporation had contracted to deliver 300,000 pounds of
tung oil to one customer, the largest order then recorded.
The other was his organization's avowed intention to set out
immediately 400,000 young nursery trees, near Lamont,
On September 11, 1939, President John J. Tigert, of the
University of Florida, announced that a two-year, $2,000
fellowship had been presented to the University by the cor-
poration. The fellowship was named in honor of Mr. William-
son, who had become a leader in tung tree research and
The University of Florida has been conducting original
tung tree research for many years, working in conjunction
with the United States Department of Agriculture research
laboratory, located in Gainesville. The fellowship has been
instrumental in adding new knowledge to what had been
already known about the tung tree and its culture, and will
be a material aid to the farmer of the future.
Further research in tung tree planting and soil adapta-
bility is of increasing importance, according to Dr. Tigert,
DEPARTMENT OF AGRICULTURE
not only because of the growing demand for tung oil by
American industry, but to assist Florida farmers in growing
and harvesting a profitable cash crop.
Tung Oil Importations
Tung oil ranks tenth among the primary animal and
vegetable fats and oils used by American industry, in the
composition of manufactured products. American imports
of tung oil, mostly from China, reached a peak in 1937, and
have declined sharply since then. As a result consumption
of tung oil has followed the same trend. In 1937 a total of
120,378,000 pounds were used, but in 1940 the total had
dropped to 59,057.000 pounds. More than 174,884,000 pounds
were imported in 1937, while in 1940 imports amounted to
less than 97,049,000 pounds. The above information was con-
tained in a booklet, Animal and Vegetable Fats and Oils,
released by the U. S. Department of Commerce in 1941.
Importations for the five-year period 1936-1940 were as
1936: 154,829,996 pounds.
1937: 174,884,805 pounds.
1938: 107,455,674 pounds.
1939: 78,717,634 pounds.
1940: 97,048,595 pounds.
Industrial consumption of tung oil for 1940 was as follows:
Trade Pounds Tung Other Oils
Paint and Varnish
industry ......................... 54,611,000 12.6 87.2
Linoleum and Oil Cloth
industry ............................. 2,064,000 1.8 98.2
Printing Ink industry...... 1,728,000 8.2 91.8
Miscellaneous industries 654,000 ..................
48 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
1939 PRODUCTION OF TUNG NUTS IN FLORIDA
hI I <.,2s Di
The State .................
B ay .............................
C itrus ....................
C la y .............................
D u v a l ...........................
F franklin .....................
G ilchrist .....................
G u lf .............................
H olm es .......................
Indian River .........
367 758,935 449,829 51
367 758,935 449,829 51
12,293 185,313 13 578,575
(1) (1) 1
31 97,730 831 5
DEPARTMENT OF AGRICULTURE
Jefferson ......... 10
Lafayette ................ 2
L a k e .............................. 2
L e e ...... ......................
Leon .. ..................... 6
L e v y ............................. 3
L ib erty ........................
M adison ..................... 3
M arion ........................ 39
Martin ................... 1
N assau ........................ 2
Okaloosa .................. 27
O range ........................ 2
Palm Beach ............
P a sco ........................... 2
P in ellas .....................
P o lk ............................. 1
Putnam ........................ 12
St. Johns ..................
St. L ucie ..................
Santa Rosa ............ 18
Sem inole .....................
Sum ter ........................ 3
Suwannee .................. 23
T ay lo r ......................... 1
U nion ........... ........
Volusia ........................ 13
W akulla .....................
Walton ........................ 19
Washington ............ 1
(1) Where there are less
in the State totals.
"- Po .b .t
172,060 86,004 3
(1) (1) 1
1,794 28,017 2 10,002
than 3 farms reporting, data are included only
50 TUNG OIL-AN ESSENTIAL DEFENSE INDUSTRY
NUMBER OF FLORIDA TUNG TREES AND FARMS
Farms Reporting ........................
Trees not of bearing age......
Trees of bearing age...............
Pounds of Nuts Harvested...
U. S. STOCKS OF TUNG OIL
(Quantities in 1,000's of pounds)
March 31 ........................
J u n e 3 0 ...........................
September 30 ...........
December 31 ............
U. S. CONSUMPTION OF TUNG OIL
(Quantities in 1,000's of pounds)
Jan. 1 to Mar. 31......
Apr. 1 to June 30...
July 1 to Sept. 30...
Oct. 1 to Dec. 31......
U. S. FACTORY CONSUMPTION OF TUNG OIL,
(Quantities in 1,000's of pounds)
1936 1937 1938
Total ................................. 107,875 120,378 87,415
Varnishes ............... 94,642
Oilcloth ..................... 7,131
Printing Inks ............ 2,331
Products .................. 3,769
105,731 78,310 82,307
7,198 4,131 3,763 2,064
2,762 2,084 2,105 1,728
4,687 2,890 2,545
DEPARTMENT OF AGRICULTURE
American Tung Tree, Propagation and Production, Joseph C. Adderley,
published by American Tung Oil Institute, Pensacola, Fla., 1936.
Producing Tung Oil in Florida, Bulletin No. 11, Florida Department of
Agriculture, Tallahassee, 1935.
The Tung Oil Tree, Bulletin No. 280, Florida Agricultural Experiment
Station, Gainesville, 1935.
A Preliminary Report on Zinc Sulphate as a Corrective for Bronzing
of Tung Trees, Bulletin No. 273, Florida Agricultural Experiment
A Preliminary Report on Frenching of Tung Trees, Bulletin No. 318,
Florida Agricultural Experiment Station, 1937.
Some Results of a Study of the Tung Oil Industry in the United States,
Farm Credit Administration, Washington, D. C., 1935.
Tung Oil Culture, Questions and Answers, National Paint, Varnish and
Lacquer Association, Inc., Washington, D. C., 1937.
Tung Oil, Bulletin No. 133, Bureau of Foreign and Domestic Com-
merce, U. S. Department of Commerce, Washington, D. C., 1932.
Tung Oil, Synopsis of Information, Bureau of Foreign and Domestic
Commerce, U.S.D.C., Washington, D. C., 1938.
Recent Developments in Growing American Tung Oil. Circular No. 622,
National Paint, Varnish and Lacquer Association, Inc., 1939.
Soils and Tung Trees, Matthew Drosdoff, U. S. Department of Agri-
culture. Circular No. 622, National Paint, Varnish and Lacquer
Association, Inc., 1939.
Tung Oil Industry in Florida, Federal Writers' Project of Florida.
Bulletin No. 11, Florida State Department of Agriculture, 1939.
Flowering, Fruiting, Yield and Growth Habits of Tung Trees, R. F.
Dickey and Walter Reuther, Bulletin No. 343, University of
Florida Agricultural Experiment Station, 1940.
Scientific and Research Work to Remove Hazards and Increase Re-
turns from an Expanding New Industry, J. Francis Cooper,
Florida Grower, September, 1940.
Tung Oil Substitutes, Florida Times-Union, December 12, 1940.
Animal and Vegetable Fats and Oils, U. S. Department of Commerce,
Uncle Sam's Growing Stepchild, Florida Times-Union, July 20, 1941.
Future for Florida Tung Oil, B. F. Williamson, Florida Grower, May,
Tung Tree Planting, A Graphic Review of Florida Agriculture, July,
New Tung Oil Substitutes, Florida Times-Union, June, 1941.
Dr. C. C. Concannon, Industrial Consultant, U. S. Department of
Commerce, Letter to Dr. Carita Doggett Corse, State Supervisor,
Florida WPA Writers' Project, September 2, 1941.
Tung Oil Crop Reaches New High
The U. S. Department of Commerce regional
commerce bulletin of June 22nd, 1942, says
"the south's tung oil crop will bring nearly
four million dollars in new wealth into that
region this year, the estimate being that
the crop will yield ten million pounds of oil."