A large tree with a long, cylindrical trunk, pyramidal crown and corky wings on branches and twigs.
Leaves alternate, simple, star-shaped, with 5 (sometimes 7) lobes, 3–6 inches wide, deeply lobed; margin toothed, tips long-pointed; leaves slightly aromatic when bruised.
Bark brown to gray, very rough with deep grooves and narrow, slightly scaly ridges.
Twigs reddish- or yellowish-brown becoming gray, aromatic, often with corky wings on second-year’s growth; pores raised, dark.
Flowers April–May, with male and female flowers on the same twig; male flowers greenish-yellow, on an upright stalk in several tight, rounded clusters; female flowers in a single, drooping, round cluster about ½ inch in diameter.
Fruit matures in September–October, persists through winter; light brown, globe-shaped, formed by the union of multiple individual fruits, hard, spiny due to numerous woody, hornlike projections, 1–1½ inches in diameter.