birch, common name for some members of the Betulaceae, a family of deciduous trees or shrubs bearing male and female flowers on separate plants, widely distributed in the Northern Hemisphere. They are valued for their hardwood lumber and edible fruits and as ornamental trees. The species of Betulaceae native to the United States represent five genera— Alnus (alder), Betula (the birches), Corylus (hazel), and Carpinus (hornbeam) and Ostrya (hop hornbeam), both also called ironwood. The sixth genus, Ostryopsis, is restricted to Mongolia. The birches, beautiful bushes or trees of temperate and arctic regions, are often found mingled with evergreens in northern coniferous forests. Most American species are trees of the Northeast; a few smaller and scrub species grow in the West. The close-grained hardwood of several of the trees is valued for furniture, flooring, and similar uses (in America, particularly that of the yellow birch, B. lutea ); stained birch provides much of the so-called mahogany of lower-priced furniture. White-barked birches are often used as ornamental trees, e.g., the famous paper, or canoe, birch ( B. papyrifera ) of the N United States and Canada. Its bark, which separates in layers, was used by the Native Americans for canoes and baskets. Various birches have yielded sugar, vinegar, a tea from the leaves, and a birch beer from the sap. The sweet, or black, birch ( B. lenta ) is now the chief source of oil of wintergreen. The Betulaceae is classified in the division Magnoliophyta, class Magnoliopsida, order Fagales.