Quercus variabilis aka Chinese Cork Oak

Quercus variabilis is known as Chinese cork oak or oriental oak. This large tree belongs to the beech family, Fagaceae. Its native range includes China, Tibet, Taiwan, Japan, Korea and Vietnam. It grows in mixed woods and other forest types. It sheds its leaves and grows at a slow pace. Its upright branches form an open crown. Garden sources give heights of 60–90 feet [18.3–27.4 metres]. The crown can spread 60–75 feet [18.3–22.9 metres].

The thick bark gives this oak much of its appeal. Its gray surface has yellow tones, deep cracks and winding ridges. People harvest the bark for cork in Asia. The long, simple leaves resemble those of a chestnut. They measure 0.25–0.5 feet [0.08–0.15 metres] long. Their green upper faces contrast with white, hairy undersides. Side veins end in small bristles along the toothed edges. Young trees may keep their leaves into winter. Young twigs lose their hairs as they age. Reddish-brown scales cover the long, oval buds.

Small yellow or green flowers appear from March to June. Male flowers hang in catkins, while female flowers form clusters. The blooms add little to the tree's visual appeal. The fruit draws more notice than the flowers. Brown, round acorns take two years to reach maturity. Each acorn sits deep within a cup with soft bristles. The cup covers about two-thirds of the nut. Acorns ripen in fall, and seed provides a means of propagation.

Grow this tree in full sun and well-drained soil. It accepts some shade, but not a fully shaded site. Rich, moist loam suits it best, including sandy loam. It also grows in clay and tolerates dry soil and drought. Most sources place it in USDA zones 5–7. NC State extends that range through zone 8. Its size suits lawns, woodland gardens and sites needing shade. Chicago Botanic Garden also lists it for street use. NC State identifies it as a butterfly host plant.

Missouri Botanical Garden reports no major pest or disease problems. NC State still directs growers to common oak pest guides. Sources differ on whether upkeep is low or moderate. The acorn cups yield a black dye for silk. PFAF records tannin uses and traditional medicinal use of galls. Acorns are edible only after treatment to remove their tannins. People can grind the prepared seeds for bread or stews. NC State rates poisoning severity as low, not absent. Untreated fruit can cause gut pain and other illness. Acorns can also block the digestive tract.