Aleurites fordii Hemsl.
Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.
- Folk Medicine
- Yields and Economics
- Biotic Factors
Tung trees are cultivated for their seeds, the endosperm of which
supplies a superior quick-drying oil, utilized in the manufacture of lacquers,
varnishes, paints, linoleum, oilcloth, resins, artificial leather, felt-base
floor coverings, and greases, brake-linings and in clearing and polishing
compounds. Tung oil products are used to coat containers for food, beverages,
and medicines; for insulating wires and other metallic surfaces, as in radios,
radar, telephone and telegraph instruments.
No data available.
The fruit contains 1420%; the kernel, 5360%; and the nut, 3040% oil.
It contains 7580% a-elaeo stearic, 15% oleic-, ca 4% palmitic-, and ca 1%
stearic-acids. Tannins, phytosterols, and a poisonous saponin are also
reported (List and Horhammer, 19691979).
Trees up to 12 m tall and wide, bark smooth, wood soft; leaves dark
green, up to 15 cm wide, heart-shaped, sometimes lobed, appearing usually just
after, but sometimes just before flowering; flowers in clusters, whitish,
rosethroated, produced in early spring from terminal buds of shoots of the
previous season; monoecious, male and female flowers in same inflorescence,
usually with the pistillate flowers surrounded by several staminate flowers;
fruits spherical, pear-shaped or top shaped, green to purple at maturity, with
45 carpets each with one seed; seeds usually 45, but may vary from 1 to 15,
23.2 cm long, 1.3 2.5 cm wide, consisting of a hard outer shell and a kernel
from which the oil is obtained. Fl. Feb.Mar.; fr. late Sept. to early Nov.
High-yielding cultivars continue to be developed. Some of the best
varieties released by the USDA for growing in southern, United States are the
'Folsom': low-heading, high productivity; fruits large, late maturing, turning
purplish when mature, containing 21% oil; highest resistance to low temperature
'Cahl': low-heading, productive; fruits large, 20% oil content; matures early,
somewhat resistant to cold in fall.
'Isabel': low-heading, high productive; fruits large, maturing early, 22% oil
'La Crosser: High-heading, exceptional productivity; fruits small, late
maturing, tending to break segments if not harvested promptly, 2114% oil
content; a very popular variety.
'Lampton': outyields all other varieties; very low-heading; fruits large, early
maturing; 22% oil content.
Several other species of Aleurites are used to produce tung-oil, usually
of low quality. Aleurites cordata, Japanese wood-oil tree; A.
moluccana, Candlenut or lumbang tree; A. trisperma, Soft Lumbang
tree; none of which can be grown commercially in the United States.
Aleurites montana, Mu-tree, is the prevailing commercial species in
South China and could be grown in Florida. (2n = 22)
Native to central and western China, where seedlings have been planted
for thousands of years; planted in southern United States from Florida to
Ranging from Subtropical Dry to Moist through Tropical Very Dry to Dry
Forest Life Zones, this species is reported to tolerate annual precipitation of
6.417.3 (mean of 8 cases = 12.,3), temperature of 18.726.2°C (mean of 8
cases 22.5), pH of 5.47.1 (mean of 4 cases = 6.4) (Duke, 1978, 1979). Tung
trees are very exacting in climatic and soil requirements. They require long,
hot summers with abundant moisture, with usually at least 112 cm of rainfall
rather evenly distributed through the year. Trees require 350400 hours in
winter with temperatures 7.2°C or lower; without this cold requirement,
trees tend to produce suckers from the main branches. Vigorous but not
succulent growth is most cold resistant; trees are susceptible to cold injury
when in active growth. Production of tung is best where day and night
temperatures are uniformly warm. Much variation reduces tree growth and fruit
size. Trees grow best if planted on hilltops or slopes, as good air-drainage
reduces losses from spring frosts. Contour-planting on high rolling land
escapes frost damage. Tung makes its best growth on virgin land. Soils must
be well-drained, deep aerated, and have a high moisture-holding capacity to be
easily penetrated by the roots. Green manure crops and fertilizers may be
needed. Dolomitic lime may be used to correct excessive acidity; pH 6.06.5 is
best; liming is beneficial to most soils in the Tung Belt, the more acid soils
requiring greater amounts of lime.
Tung trees may be propagated by seed or by budding. Seedlings generally
vary considerably from parent plants in growth and fruiting characters.
Seedlings which have been self-pollinated for several generations give rather
uniform plants. Only 1 out of 100 selected 'mother' tung trees will produce
seedlings sufficiently uniform for commercial planting. However, a `mother'
tree proven worthy by progeny testing may be propagated by budding. The budded
trees, which are genetically identical with the original tree, will provide an
adequate supply of seed satisfactory for planting. Seedlings are used for the
root system for budded trees. Buds from 'mother' trees are inserted in stems
of 1-year old seedlings, 57.5 cm above surface of the soil. Later, original
seedling top is cut off and a new top grown for p the transplanted bud, making
the tops of budded trees parts of the parent tree. Usually seedling trees
outgrow budded trees, but budded trees produce larger crops and are more
uniform in production, oil content and date of fruit maturity. Tung seed are
normally short-lived and must be planted during the season following harvest.
Seeds are best hulled before planting, as hulls retard germination. Hulled
seed may be planted dry, but soaking in water for 57 days hastens germination.
Stratification, cold treatment or chemical treatment of seeds brings about more
rapid and uniform germination. Dry-stored seed should be planted no later than
February; stratified seed by mid-March; coldtreated and chemical treated seed
by early April. Seed may be planted either by hand or with a modified
corn-planter, the seed spaced 1520 cm apart, about 5 cm, in rows 1.6 m apart,
depending on the equipment to be used for cultivation and for digging the
trees. Seeds germinate in 60 days or more, hence weed and grass control may be
a serious problem. As soon as seedlings emerge, a side-dressing of fertilizer
(5105) with commercial zinc sulfate should be applied. Fertilizer is applied
at rate of 600 kg/ha, in bands along each side of row, 20 cm from seedlings and
57.5 cm deep. Other fertilizers may be needed depending on the soil. Most
successful budding is done in late August, by the simple shield method,
requiring piece of budstock bark, including a bud, that will fit into a cut in
the rootstock bar, a T-shaped cut is made in bark of rootstock at point 57.5
cm above ground level, the flaps of bark loosened, shield-bud slipped inside
flaps and the flaps tied tightly over the transplanted bud with rubber budding
stripe, 12 cm long, 0.6 cm wide, 0.002 thick. After about 7 days, rubber
stripe is cut to prevent binding. As newly set buds are susceptible to cold
injury, soil is mounded over them for winter. When growth starts in spring,
soil is pulled back and each stock cut back to within 3.5 cm of the dormant
bud. Later, care consists of keeping all suckers removed and the trees
well-cultivated. Trees are transplanted to the orchard late the following
winter. Spring budding is done only as a last resort if necessary trees are
not propagated the previous fall. Trees may be planted 125750 ha. When trees
are small, close planting in rows greatly increases the bearing surface, but at
maturity the bearing surface of a crowded row is about the same as that of a
row with trees farther apart. However, it is well to leave enough space
between row for orchard operations. In contourplanting, distances between rows
and total number of trees per hectare vary; rows 1012 m apart, trees spaced
3.34 m apart in rows, 250350 trees/ha. Tops of nursery trees must be pruned
back to 2025 cm at planting. As growth starts, all buds are rubbed off except
the one strongest growing and best placed on the tree. A bud 5 cm or more
below top of stump is preferred over one closer to top.
Tung trees usually begin bearing fruit the third year after planting,
and are usually in commercial production by the fourth or fifth year, attaining
maximum production in 1012 years. Average life of trees in United States is
30 years. Fruits mature and drop to ground in late September to early
November. At this time they contain about 60% moisture. Fruits must be dried
to 15% moisture before processing. Fruits should be left on ground 34 weeks
until hulls are dead and dry, and the moisture content has dropped below 30%.
Fruits are gathered by hand into baskets or sacks. Fruits do not deteriorate
on ground until they germinate in spring.
Trees yield 4.55 MT/ha fruits. An average picker can gather 6080
bushels of fruits per day, depending on conditions of the orchard. Fruits may
be gathered all through the winter season when other crops do not need care.
Because all fruits do not fall at the same time, 2 or more harvestings may be
desirable to get the maximum yield. Fruits are usually sacked, placed in
crotch of tree and allowed to dry 23 weeks before delivery to the mill.
Additional drying may be done at the mill, but wet fruits contain less oil
percentage-wise and prices will be lower. Prices for tung oil depend on price
supports, domestic production, imports and industrial demands. World
production in 1969 was 107,000 MT of tung nuts; in 1970, 143,000; and projected
for 1980, 199,000. Wholesale prices are about $0.276/kg; European import
prices, $0.335/kg. Growers receive about $51.10/ton of fruit of 18.5% oil
content to about $63.10/ton for fruits of 22% oil content. Major producing
countries are mainland China and South America (Argentina and Paraguay); United
States and Africa much less than the others. U.S. Bureau of Census figures
1,587,000 pounds of tung oil were consumed during February of 1982,
representing a 1,307,000 pound drop from January. The largest application for
the oil is paint and varnish, which accounted for 566,000 pounds of total
consumption in February (CMR, April 26, 1982).
During World War II, the Chinese used tung oil for motor fuel. It
tended to gum up the engines, so they processed it to make it compatible with
gasoline. The mixture worked fine (Page, 1981).
Bees are needed to transfer pollen from anthers to pistil. When
staminate and pistillate flowers are on separate trees, one staminate tree for
20 pistillate trees should be planted in the orchard. Pollination can occur
over several days. Tung trees are relatively free of insects and diseases,
only a few causing losses serious enough to justify control measures: as
Botroyosphaeria ribis, Clitocybe tabescens, Mycosphaerella aleuritidis,
Pellicularia koleroga, Physalospora rhodina and the bacterium,
Pseudomonas aleuritidis. Other bacteria and fungi reported on tung
trees are: Armillaria mellea, Botryodiplodia theobromae, Cephaleures
virescens, Cercospora aleuritidis, Colletotrichum gloeosporioides, Corticium
koleroga, Fomes lamaoensis, F. lignosus, Fusarium heterosporum forma
aleuritidis, F. oxysporum, F. scirpi, F. solani, Ganoderma pseudoferreum,
Cloeosporium aleuriticum, Glomerella clngulata, Pestalotia dichaeta,
Phyllosticta microspore, Phytomonas syringas, Phytophthora omnivora, Ph.
cinnamomi, Poria hypolateritia, Pythium aphanidermatum, Rhizoctonia solani,
Septobasidium aleuritidis, S. pseudopedicellatum, Sphaerostilbe repens,
Uncinula miyabei, var. aleuritis, Ustilina maxima, U. zonata.
Insect pests are not a serious problem, since fruit and leaves of tung trees
are toxic to most animal life. Nematodes Meloidogyne spp. have been
reported (Golden, p.c. , 1984).
Complete list of references for Duke, Handbook of Energy Crops
- Duke, J.A. 1978. The quest for tolerant germplasm. p. 161. In: ASA
Special Symposium 32, Crop tolerance to suboptimal land conditions. Am. Soc.
Agron. Madison, WI.
- Duke, J.A. 1979. Ecosystematic data on economic plants. Quart. J. Crude Drug
- Golden, A.M. 1984. Personal communication regarding nematodes. Beltsville,
- List, P.H. and Horhammer, L. 19691979. Hager's handbuch der pharmazeutischen
praxis. vols 26. Springer-Verlag, Berlin.
- Page, J. 1981. Sunflower power. Science 81 July/Aug: 9293.
Last update December 19, 1997