Birch trees are part of the birch family, along with hophornbeams, hornbeams and alders. The birches are a medium-sized group of trees and shrubs. With 60 species worldwide, the birch tree grows in northern temperate regions from Japan to Spain and across North America. Birches include the yellow birch, cherry birch, river birch, paper birch, water birch and gray birch.
Birch trees have simple leaves with toothed edges called margins. On the yellow birch, the leaves are oval shaped. On cherry and paper birches, the leaves are egg shaped, which is called ovate. River birch leaves are also ovate but with slightly sharp lobes. Water birch leaves are oval. Gray birch leaves are triangular with a rounded base. Birch leaves range in color from grass green to dark green during the growing season, turning yellow in the fall.
Birch trees are recognizable by their bark, which peels off in strips in all birches except the gray birch. The bark of the paper birch ranges in color from white to pink and papery. River birch bark is pinkish brown. The bark of young yellow birch trees is golden yellow. Cherry birch bark is red. Gray birch bark is off-white but doesn't peel. Water birch bark is red-brown or purple-brown and shiny.
Both male and female flowers bloom on the same tree in the birch family. Male flowers, called catkins, bloom in the late summer or fall, according to the "Field Guide to Trees of North America," by the National Wildlife Federation. They bloom in erect clusters at the tips of long shoots and persist through winter. In the spring, the number of male catkins quadruple in length and droop from the branches. Female flowers bloom in pairs or singly in the early spring before the leaves.
Birch tree timber is used for a variety of construction projects. Gray birch timber is used in woodworking and for fuel, according to the United States Department of Agriculture Forest Service. River birch timber is used for furniture construction, basketware and for fuel. Yellow birch timber is widely used for furniture, interior finishing, tool handle construction, cabinetry and interior woodwork such as doors. Water birch is used for firewood and posts. Paper birch is used for plywood, veneer, furniture, cabinetry and for fuel. Water birch is used for furniture, millwork and interior finishing.
Birches are used as a food source by birds and animals. Beavers and porcupines eat gray, yellow and paper birch and build dams with water birch. White-tailed deer eat gray, river and paper birch. Moose and snowshoe hares eat gray, yellow and paper birch. Birds such as the ruffled grouse and chickadee eat the seeds of the gray, river and water birch. Turkeys eat the seeds of the river birch. Red squirrels eat the sap of both the yellow and paper birch. Sheep and goats eat the water birch. Butterflies are attracted to the cherry birch.