The birch family is a family of trees and woody shrubs, scientifically classified as the family Betulacea. The genus Betula is the parent genus for the true birches, though modern science generally recognizes two subfamilies within the birch family, six genera, and approximately 130 species. These include birches, alders, hornbeams, and several nut-bearing trees like filberts and hazels. Birches have long been important for the wood and nuts that they produce.
This family of trees is believed to have originated in prehistoric China, as all six genera and more than 50 species are found in this area, many of which are endemic to the region. Fossil examples from this region of all six genera date back as far as 20 million years. Today, these trees are found in nearly all temperate zones around the world, primarily in the Northern hemisphere, although a few species are known from the Andes mountains in South America.
Many members of the birch family are regarded as pioneer species. These types of trees are often the first to establish themselves in areas cleared by wildfires and other disturbances. They may colonize terrain like heathland and damp lowlands, as many species are tolerant of wet conditions. Most members of the birch family have teardrop shaped leaves with feather-pattern ribbing and serrated edges. All are monoecious, or have male and female flowers on the same tree.
Members of the birch family have long been important commercially for nuts, lumber, and other wood products. Filberts and hazelnuts are important food crops. Pre-industrial peoples like the native Americans used birch bark for covering canoes and dwellings and as a medium for writing and painting. Wood from some species, like the hornbeams, is particularly hard and durable and in the past was used for things like tools, wagon wheels, and chopping boards.
Today, alder and birch remain popular for furniture, paneling, hobbies, and veneers. Much finish- or cabinet-grade plywood is made with an outer layer of birch. Extracts from some species are used in cosmetics, shampoos, and flavorings, and birch beer is a traditional non-alcoholic carbonated brew. Birch is also a popular firewood, as it burns cleanly and has a high caloric value for its weight. Wood from species like the hornbeam continues to be used to construct items such as tool handles, wooden pegs, and flooring, for which a very hard, durable wood is desirable.