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Tung is a gracefully spreading round-crowned deciduous tree that may grow to 30-40 ft (9.1-12.2 m), but usually stays half that size. The smooth brownish-gray branches arch and fork with a tropical flair, bearing alternate heart-shaped 3-5 in (7.6-12.7 cm) dark green leaves on long reddish petioles. The leaves never quite unfold all the way and have deeply incised veins that make them look almost pleated. Young trees may have larger, flatter leaves with three pointed lobes. The sap is milky white. The flowers open before the leaves come out in early spring, decorating the bare branches with eye catching ruffly looking clusters of pale peach-colored blossoms. Examined closely, the 1.5 in (3.8 cm) blooms resemble those of a catalpa Catalpa bignonioides. They have 5-7 round tipped ivory petals delicately streaked with rust-orange in the throat, creating a color effect reminiscent of peach ice cream. They are borne in long-stemmed clusters consisting of about 60 flowers. On most trees, all but one in each cluster are staminate male flowers. Upon pollination by honeybees, the female flowers develop into 2-3 in (5.1-7.6 cm) hard roundish green or purplish-green fruits that may contain 1-15 nut-like seeds, but usually have about five. They ripen in the fall as the foliage turns creamy yellow. The closely related candlenut tree (A. molucanna) has petals less than 0.5 in (1.3 cm) long and fruits with just 1-2 seeds.
Tung comes from the rocky subtropical foothills of western China. It is cultivated in China, Argentina, Paraguay, and, to a much lesser extent, Africa and the southeastern United States. There are naturalized populations around abandoned commercial tung oil groves in the vicinities of Tallahassee, Gainesville, and Marianna, Florida; Bogalusa, Louisiana; and Poplarville, Mississippi.
Culture
Moisture: Tung can take drought, but it does much better in reliably moist soil. Hardiness: USDA Zones 8 - 10. Although the buds and succulent new growth are susceptible to frost damage, hardened-off trees can withstand freezes down to 18 ºF (-8ºC) or lower. Tung grows best where summers are long and hot and temperatures are consistently warm day and night throughout the growing season, but they still require some winter chilling. 350-400 hours below 45ºF (7.2ºC) each winter is ideal. In more tropical climates, the trees tend to produce suckers from the main branches. A hillside site with good air drainage limits freeze damage during cold spells. Propagation: Seedling tung trees typically outgrow those that are vegetatively propagated, but because tung trees grown from seed are extremely variable and often bear little resemblance to the parent plant, budding is the preferred method of propagation. Buds from a selected mother tree are inserted into the stem of a one-year-old seedling 2-3 in (5.1-7.6 cm) above the soil surface. Later, the original seedling top is cut off and the transplanted bud is grown into a new leader. Budding is best done in late August, by the simple shield method, which requires that a piece of budstock bark (including a bud) be fit into a T-shaped cut in the seedling bark. Soil should be mounded over the buds to protect them from cold the first winter. When the tree is ready to start growing in the spring, this extra soil should be raked away from the stem and the original stem should be cut back to within 1-2 in (2.5-5.1 cm) of the new bud. Cuttings of mature wood may also be rooted in a coldframe. If seeds are to be used, the nuts should be hulled and planted within a few months after they mature, since they lose viability quickly in storage. Soak them in water for 5-7 days, then plant them where they are to grow. Alternatively, seeds may be sown in a warm greenhouse in the very early spring to produce transplants to be set out late the following spring. Germination takes at least two months. If the trees are started outdoors, a summer side-dressing of 5-10-5 with zinc sulfate is recommended.
Tung was formerly cultivated primarily for its oil, but it also makes a lovely ornamental tree. The oil pressed from tung seeds makes an exceptionally fine wood finish. Often sold under the name "teak oil", tung oil dries quickly to form a tough, glossy, waterproof surface. Tung oil is also used as a drying agent for paints and varnishes; as waterproofing for paper, cloth, and ceramic products; and in the manufacture of linoleum, oilcloth, inks, resins, artificial leather, lubricants, brake linings, and cleaning and polishing compounds. It is used in coatings for food containers and electronic parts. During World War II, the Chinese developed a way to process tung oil to supplement gasoline for motor fuel. Legend has it that their ancestors used it to seal the Great Wall. Although it is dangerously toxic, tung oil has been used to treat skin conditions and constipation. Tung extracts have recently shown potential as termite control compounds.
Features
Linda Conway Duever 8/13/00; updated 3/24/04, 3/30/04
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