Trees and some bushes with alternate, simple and toothed leaves. The tiny male and female flowers are on the same plant, have no petals and sometimes no sepals. The male flowers are in drooping, slender catkins and the female flowers are in spikes or heads. Includes the birches (Betula genus), with fruits that are 1-seeded nuts in cone-like clusters (some have bark peeling in papery layers); hornbeams (Carpinus genus), with smooth, fluted bark and hanging clusters of bracts concealing nuts in their axils; hop-hornbeams (Ostrya genus), with shredding bark and small nuts enclosed in papery capsules; alders (Alnus genus) that characteristically have male and female catkins and mature seed-bearing cones present at the same time; and hazelnuts (Corylus genus), bushes with nuts enclosed in flattened, hairy green husks with ragged lower margins.
This family contains trees.