any of about 25 species of hardy, slow-growing ornamental and timber trees constituting the genus Carpinus of the birch family (Betulaceae), distributed throughout the Northern Hemisphere. The hop-hornbeam (q.v.) is in a different genus of the birch family. A hornbeam has smooth, grayish bark, a short, fluted trunk, and horizontally spreading branches. It differs from other trees in the birch family in that male catkins are not formed until the spring in which they mature. A leaflike, three-lobed husk surrounds each fruit, a nutlet about 1 cm (12 inch) long. The egg- or lance-shaped alternate leaves may remain on the tree into winter.
Learn more about hornbeam with a free trial on Britannica.com.