Vernicia fordii aka Chinese Wood Oil Tree

Tung oil tree, Vernicia fordii, is a member of the spurge family, Euphorbiaceae. Older references list it as Aleurites fordii. Other common names include tung tree, tung nut and China wood oil plant. It grows wild from central and southern China into Myanmar and northern Vietnam. There it occupies open mountain forest and rocky foothills, up to about 6,500 feet (2,000 m). The species name honours Charles Ford, a nineteenth-century superintendent of the Hong Kong Botanic Garden.

In gardens this is a small tree of about 15 to 25 feet (4.5 to 7.5 m) tall. It spreads 10 to 15 feet (3 to 4.5 m) under a rounded, spreading crown. Some sources report trees of 40 feet (12 m), and one cites 65 feet (20 m) in the wild. Sources disagree on whether it keeps its leaves, but most describe it as deciduous. Growth is medium to fast.

The bark is thin and smooth, brownish grey or greenish grey, with reddish dots. Cut stems bleed a milky sap. Twigs are dark grey-brown, marked with reddish lenticels and round leaf scars. The large, long-stalked leaves are heart-shaped and sometimes shallowly three-lobed. They reach 6 to 10 inches (15 to 25 cm) long and turn yellow in autumn. Two red glands sit where each leaf meets its stalk.

Flowers open in late winter or early spring, before or as the leaves appear. They are pale pink to white with red veins or a red centre, and grow in large clusters. Bees visit and pollinate them. The rounded green fruits are 2 to 3 inches (5 to 7.5 cm) across. They ripen in autumn and hold four or five large seeds. Late frosts can kill the flower buds, so a later-blooming selection was bred for orchards.

The tree wants full sun but tolerates light shade. It needs fertile, well-drained loam or sandy loam with steady moisture, slightly acidic for preference. Once settled it copes with some drought. It is hardy only in USDA zones 8 to 10 and dislikes cold. Few pests trouble it, though dieback and canker can occur.

Growers value the seeds for tung oil, a fast-drying oil used in varnish, lacquer, paint and wood finish. Gulf Coast farms in the United States once grew it on a large scale. Freezes, hurricanes and synthetic resins ended that trade, though interest is returning in Florida. In warm areas it also serves as a flowering specimen or small shade tree. Abandoned groves have seeded into woodland edges, and the tree spreads by suckers. Several southern states now treat it as a weed. Removing a tree completely is hard work.

All parts of the tree are poisonous, and the seeds carry the greatest risk. Eating them can cause stomach pain, vomiting and diarrhoea. The sap can also irritate the skin. One source mentions the seed as food, but the poison risk outweighs that report. Do not eat any part.