There are around 60 different species of birch. Birch are deciduous trees that require well-drained soil, adequate moisture and direct sunlight. These trees usually grow near lakes and rivers. Birch have smooth, multicolored or white bark marked with horizontal pores, that usually peel in thin horizontal strips, especially on younger trees; on more mature trunks the thick, jagged bark breaks into irregular pieces. They have slender branches that rise into a narrow pyramidal canopy when they are young; as they mature their canopy becomes horizontal, often weeping. The bright green leaves have toothed margins and are oblong to triangular; the leaves are arranged alternately on the branchlets. The foliage turns yellow in the fall. The male catkins are drooping and flower before the leaves emerge; the smaller female cone-like catkins are upright on the branches. As the female cones disintegrate, they release tiny, one-seeded, winged nutlets.