Common Name: Tung Tree

General Information

Vernicia fordii is an evergreen tree with a spreading, round crown; it can grow up to 9 metres tall.
The tree yields a very valuable oil that has a wide range of applications and various medicinal properties. It is often cultivated, both within and outside its native range, for this oil. The tree is also considered to be very ornamental[, , ].

Known Hazards

The oil from the seed is poisonous[]. The leaves and seeds contain a toxic saponin[]. Although poisonous, saponins are poorly absorbed by the human body and so most pass through without harm. Saponins are quite bitter and can be found in many common foods such as some beans. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of food that contain saponins. Saponins are much more toxic to some creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish[].

Botanical References

, ,

Range

E. Asia - southern China, Myanmar, Vietnam

Habitat

Base of foothills esp. in rocky places, at elevations up to 1,000 metres in W. China[]. Montane sparse forests; at elevations from 200 - 1,500 metres, occasionally to 2,000 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	7.00 m
Pollinators	Bees
Self-fertile	Yes
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Tung tree is a plant mainly of subtropical areas, though it can also be grown at higher elevations in the tropics and in some of the warmer regions in the temperate zone - it is cultivated in the Caucasus, for example, where it has been sufficiently cold- resistant and withstood markedly low temperatures without any ill effects[]. It is reported to tolerate an annual precipitation of 64 - 173cm, average temperatures ranging from 18.7 - 26.2°c, and a pH of 5.4 - 7.1[]. Tung trees are very exacting in climatic and soil requirements[]. They require long, hot summers with abundant moisture, with usually at least 1,120mm of rainfall rather evenly distributed through the year[]. Trees require 350 - 400 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 the most cold resistant - trees are susceptible to cold injury when in active growth[].
Succeeds in full sun and in dappled shade. One report says that the plant is very tolerant of soil conditions[]. It is easily grown in a loamy soil but the plants are unable to withstand much frost[]. Requires a lime-free soil[].
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 10 - 12 years. Average life of trees in United States is 30 years. Fruits mature and drop to the 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 3 - 4 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[].
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 6.0 - 6.5 is best; liming is beneficial to most soils in the Tung Belt, the more acid soils requiring greater amounts of lime[].
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[]. 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[].
This species can hybridize with Vernicia montana in the wild[].
There are some named varieties[].

Edible Uses

Seed[]. There are no more details but the report should be treated with caution since the oil from the seed is said to be poisonous[].

Medicinal

The oil from the seed is used externally to treat parasitic skin diseases, burns, scalds and wounds[]. The poisonous oil is said to penetrate the skin and into the muscles, when applied to surgical wounds it will cause inflammation to subside within 4 - 5 days and will leave no scar tissue after suppressing the infection[].

The plant is emetic, antiphlogistic and vermifuge[, ].

Extracts from the fruit are antibacterial[].

Other Uses

The seed contains up to 58% of a superior quick-drying oil that is used in the manufacture of lacquers, varnishes, paints, linoleum, oilcloth, resins, artificial leather, felt-base floor coverings, 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[, , , , , ]. 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[]. The oil is very resistant to weathering[]. The oil is said to have insecticidal properties[]. The fruit is a hard, woody, pear-shaped drupe, 4 - 8cm across, containing usually 4 to 5 large, oily seeds. The fruit contains between 14 - 20% oil, the kernel 53 - 60% and the nut 30 - 40%[, ]. The oil contains 75 - 80% a-elaeo stearic, 15% oleic-, ca 4% palmitic-, and ca 1% stearic-acids[]. Tannins, phytosterols, and a poisonous saponin are also reported[]. Trees yield 4.5 - 5 tonnes of fruit per hectare[].

Propagation

Seed - sow early to mid spring in a warm greenhouse. When large enough to handle, prick the seedlings out into individual pots and grow them on for at least the first winter in a greenhouse. Plant out in early summer and give the plants some protection from the cold for their first winter outdoors. 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 5 - 7 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 late winter; stratified seed by mid-early spring; cold-treated and chemical treated seed by early mid spring[].
Cuttings of mature wood in a frame[].
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 5 - 7.5 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[]. Spring budding is done only as a last resort if necessary trees are not propagated the previous fall[].