Quercus alba aka White Oak

White oak, Quercus alba, is a large deciduous tree in the beech family, Fagaceae. It grows wild from southeast Canada through the central and eastern United States. Its range runs from Maine to Florida and west to Minnesota and Texas. In the wild it grows on dry upland slopes as well as in valleys and ravines. It is the state tree of Illinois, where it once dominated the oak savannas.

In gardens it reaches 50 to 80 feet (15 to 24 m) tall, with a spread about as wide. Wild trees can top 100 feet (30 m), and the record approaches 135 feet (41 m). Young trees have a pyramid shape. With age the crown becomes broad and rounded, with irregular, wide-spreading branches. Trees live a long time, and specimens over 300 years old are not rare. The trunk can reach 6 feet (1.8 m) across.

The bark is pale ashy grey to whitish. It is scaly and breaks into flat plates or blocks that flake with age. The species name alba means white and refers to this bark colour. The leaves are alternate and simple, 4 to 9 inches long, with 5 to 9 deep, rounded lobes and no bristles. New leaves open pinkish and mature to green or blue-green, with pale undersides. Autumn colour comes late and ranges from brown to wine-red. Some brown leaves hang on into winter.

The tree is monoecious and wind-pollinated. Male flowers hang in yellow-green catkins 2 to 4 inches long in spring. Small reddish female flowers sit in the leaf axils. The oval acorns grow 3/4 to 1 inch long, with a warty, bowl-shaped cap. They ripen in a single season and fall in autumn. Squirrels, birds and other wildlife eat them.

White oak grows best in full sun or light shade. It prefers deep, moist, well-drained, acidic loam but tolerates clay, sand and rocky ground. Once established it handles drought fairly well, but it dislikes wet sites and compacted soil. High pH can cause iron chlorosis. It is hardy in USDA zones 3 to 9 and rated H7 in the UK. Growth is slow, and a deep taproot makes moving larger trees hard. Plant it young, and propagate it from seed.

Use it as a shade tree for parks and large lawns. Keep it away from buildings and paving. The tree hosts many moth and butterfly caterpillars. The heavy, durable wood goes into flooring, furniture and whisky barrels. Native Americans used the bark and acorns as medicine.

Many pests visit white oak, but they rarely do serious harm. Diseases include oak wilt, anthracnose, powdery mildew, honey fungus and oak leaf blister. Pests include scale, leaf miners, lace bugs, aphids and galls. Gypsy moth caterpillars favour this oak and can strip it badly. The acorns are edible once the tannins are leached out, and they taste fairly sweet. Leaves and acorns contain tannins that can poison horses and other animals.