(genus Betula), deciduous monoecious trees and shrubs of the Betulaceae family. The bark of the trunk ranges in color from white to black. The leaves are sequential, simple, and petiolate. The staminate flowers, with two bifurcated stamens, are gathered in hanging catkins, which in summer are formed at the ends of annual shoots. Pistillate flowers without perianths, usually in threes (in dichasia) in axils of bracteal husks, are gathered in single catkins, which are displayed in the spring of the year, when they blossom in axils of young leaflets. The birch tree blooms in early spring, almost simultaneously with the opening of the leaves. The fruit is one-seeded, nutlike, flat, and two-winged. Seeds ripen in the summer or fall. The birch tree generally grows rapidly, particularly when it is young. It readily populates areas in which other vegetation does not exist and is often a pioneer species.
There are about 100 (more, by some data) polymorphous species growing in the temperate and cool regions of the northern hemisphere and the mountains of the subtropics; there are about 50 species in the USSR. Many birches are economically important—the valuable lumber-forming and decorative species, particularly the European white birch (Betula pendula or B. verrucosa), the Old World white birch (B. pubescens), the flat-leaf birch (B. platyphylla), the ribbed, or yellow, birch (B. costata), and the Schmidt, or iron, birch (B. Schmidtii). Most species of birch require light, are quite drought- and frost-resistant, and grow in many types of soil. The lumber and bark of many birch species are used in various sectors of the economy. The buds and leaves of the European white birch and Old World white birch are used for medicinal purposes. The buds, which contain 3.5–6 percent essential oil, are sometimes used in infusions as a diuretic and externally as a massage for aches in joints. The most prevalent species of birch is the European white birch. Trees reach 25 m in height and 80 cm in diameter. Birches tolerate a certain amount of salinization of the soil and aridity of the air; they live to 150 years and more. They are observed to 65° N lat. in Western Europe; in the USSR, they are found throughout nearly the entire forest and forest-steppe zone of the European part, western Siberia, Transbaikal, Saiany, Altai, and the Caucasus. Birches grow in combination with coniferous and deciduous varieties. In some places they form vast birch forests; and in the forest-steppe zone of the Trans-Volga Region and western Siberia, they form the so-called birch groves, which alternate with fields and steppe areas. Birches are used as field-protecting strips and as decoration. The lumber is prized for furniture production; it is used for veneer and various articles.
A. P. SHIMANIUK