Tall tree. Leaves not opposite each other, oval, not toothed, with long point at end. Branches with stout thorns. Sap is milky, and causes allergic reactions in some people. Bark orange-brown, furrowed and fibrous. Male and female flowers are on separate trees. Male flowers 4-parted, green in ball-like clusters. Female flowers also green and 4-parted, but in dense balls with long female parts hanging out, making it look like a fright wig. Blooms in mid to late spring. Fruits are bizzare grapefruit-sized green lumps that look vaguely like brains.

Originally native only to the area where Texas, Oklahoma and Arkansas come together (the homeland of the Osage tribe). Widely planted in the eastern US and frequently escaping. In Wildwood, at least one male tree, along the Bikeway between the South Bridge and the Park Road entrance. No females known.

The only tree that occurs in the wild in the eastern US with thorns and milky sap. The leaves, although dull, are good for identification. In Wildwood could be confused with hawthorns, but these are shrubs and have quite different leaves.