A round-headed tree 30 to 50 ft high, similar in habit to O. carpinifolia; young shoots furnished with gland-tipped hairs. Leaves 2 to 41⁄2 in. long, 1 to 2 in. wide, oval-lanceolate, rounded or sometimes slightly heart-shaped at the base, taper-pointed, sharply toothed (not so markedly double-toothed as in O. carpinifolia); dark green and hairy on the midrib and between the veins above, paler and more downy beneath; stalk 1⁄4 in. long, glandular downy. Male catkins 2 in. long. Fruit clusters 11⁄2 to 21⁄2 in. long, 2⁄3 to 11⁄2 in. wide. Nutlet 1⁄3 in. long, the pale bladder-like membranous bag enclosing it being ovate, 3⁄4 to 1 in. long, hairy at the base.
Native of eastern N. America; introduced by Compton, Bishop of London, in 1692. Cultivated specimens differ from the closely allied O. carpinifolia in the glandular hairs on the twigs and leaf-stalks, in the usually fewer ribs of the leaf, and in the larger nut. The timber, as the common name denotes, is very hard and durable, and is used for mallets, handles of tools, etc. Although not very common in English gardens, this interesting tree thrives well.
The following specimens have been recorded: Kew, Pagoda Vista, 45 × 33⁄4 ft (1963), by the Main Gate, 40 × 31⁄2 ft (1965); University Botanic Garden, Cambridge, 40 × 2 ft (1969); Westonbirt, Glos., 47 × 33⁄4 ft (1965); Edinburgh Botanic Garden, 36 × 21⁄2 ft (1967); East Bergholt Place, Suffolk, 33 × 4 ft (1972).