Post oak is a small to medium-sized tree with a broad, rounded crown and stout, sometimes contorted branches.
Leaves are alternate, simple, 4–7 inches long, 3–4 inches wide, leathery; with 3–5 lobes, middle lobes squarish, resembling a cross, the end lobe often 3-notched, notches between lobes deep, rounded; upper surface dark green; lower surface paler, with tiny star-shaped hairs.
Bark is gray, irregularly grooved, ridges narrow, rough with platelike scales.
Twigs are stout, densely hairy during most of the season.
Flowers April–May. Male and female flowers are on the same tree; male flowers in drooping catkins, female flowers small and in leaf axils.
Fruits September–October, acorns solitary or paired; nut brown, broadest at the base and tapering to a rounded tip ½–¾ inch long, less than ½ inch wide; cup covering ⅓–½ of the nut, bowl-shaped, hairy on the outside; scales thick, flattened, or somewhat indented, hairy; acorns ripen in autumn of the first year.
Height: to 70 feet.
Habitat and Conservation
Occurs in mostly dry to rocky upland woodlands and glades; also in flatwoods on broad ridges and lowland terraces where it is typically the dominant tree. A slow-growing, drought-resistant tree, it is difficult to transplant and does better on sites where it is already found growing. Post oaks can live 300 years or more.
The wood is used for railroad ties, furniture, general construction, and fuel. The limbs are sturdy and durable and were favored by pioneers for fence posts, hence the name; this tree played an important role in the success of American pioneers. The bark of most oaks, including this one, has astringent properties, and bark tea was used to treat a number of ailments.
Acorns are eaten by blue jays, woodpeckers, wood ducks, wild turkeys, ruffed grouse, bobwhites, mice, squirrels, raccoons, and deer.