Plants in the genus Carpinus are commonly called Hornbeams. They are relatively small hardwood trees. The 30 - 40 species occur across much of the north temperate regions, with the greatest number of species in east Asia, particularly China. Only two species occur in Europe, and only one in eastern North America.
The European Hornbeam (Carpinus betulus), is a small to medium sized tree, typically 10 - 20 m tall but occasionally reaching 30 m. It is native to most of Europe except for northern Britain and most of Scandinavia. The leaves are 5 - 9 cm long, and the seeds have a 3 - 4 cm long trilobed bract.
In general Hornbeam leaves are deciduous, alternate, and simple with a serrated margin, and typically vary from 3 - 10 cm in length. The flowers are wind-pollinated pendulous catkins, produced in spring. The male and female flowers are on separate catkins, but on the same tree (monoecious). The fruit is a small nut about 3 - 6 mm long, held in a leafy bract; the bract may be either trilobed or simple oval, and is slightly asymmetrical. The asymmetry of the seedwing makes it spin as it falls, improving wind dispersal. The shape of the wing is important in the identification of different hornbeam species. There are typically 10 - 30 seeds on each seed catkin.
The wood of hornbeams is very hard, giving rise to the name iron-wood and not used much due to the difficulty of working it. Its hardness has however lent it to use for carving boards, tool handles, coach wheels and other situations where a very tough, hard wood is required. It is sometimes coppiced to provide hardwood poles.
The common English name of "hornbeam" derives from the hardness of the wood (likened to horn) and the Old English beam, a tree (cognate with German "baum").