Birch species are generally small to medium-size trees or shrubs, mostly of northern temperate climates. The simple leaves may be toothed or pointed. The fruit is a small samara, although the wings may be obscure in some species. They differ from the alders (Alnus, other genus in the family) in that the female catkins are not woody and disintegrate at maturity, falling apart to release the seeds, unlike the woody cone-like female alder catkins.
The bark of all birches is characteristically marked with long horizontal lenticels, and often separates into thin papery plates, especially upon the Paper Birch. It is practically imperishable, due to the resinous oil which it contains. Its decided color gives the common names Red, White, Black, Silver and Yellow to different species.
The buds form early and are full grown by midsummer, all are lateral, no terminal bud is formed; the branch is prolonged by the upper lateral bud. The wood of all the species is close-grained with satiny texture and capable of taking a fine polish; its fuel value is fair.
The leaves of the different species vary but little. All are alternate, doubly serrate, feather-veined, petiolate, and stipulate. Apparently they often appear in pairs, but these pairs are really borne on spur-like two-leaved lateral branchlets.
The ripened pistillate ament is called a strobile and bears tiny winged nuts, packed in the protecting curve of each brown and woody scale. These nuts are pale chestnut brown, compressed, crowned by the persistent stigmas. The seed fills the cavity of the nut. The cotyledons are flat and fleshy. All the species are easily grown from seed.
Birches of North America include:
Birch wood is fine-grained and pale in colour, often with an attractive satin-like sheen. Ripple figuring may occur, increasing the value of the timber for veneer and furniture-making. The highly-decorative Masur (or Karelian) birch, from Betula verrucosa var. carelica has ripple texture combined with attractive dark streaks and lines. Birch wood is suitable for veneer, and birch ply is among the strongest and most dimensionally-stable plywoods, although it is unsuitable for exterior use.
Due to birch pulp’s short-fibre qualities, this hardwood can be used to make printing paper. In India the thin bark coming off in winter was used as writing paper. This has excellent life. The paper is known as bhoorj patra. Bhoorj is the Sanskrit name of tree and patra means paper. This bark also has been used widely in ancient Russia as note paper (beresta) and for decorative purposes and even making footwear — lapti.
Extracts of birch are used for flavoring or leather oil, and in cosmetics such as soap or shampoo. In the past, commercial oil of wintergreen (methyl salicylate) was made from the Sweet Birch (Betula lenta). Birch tar or Russian Oil, extracted from birch bark, is thermoplastic and waterproof; it was used as a glue on, for example, arrows, and also for medicinal purposes.
Silver Birch (Betula pendula) is Finland's national tree. Occasionally one uses leafy, fragrant twigs of silver birch to gently beat oneself in a sauna. The twigs are called vihta or vasta. This has a relaxing effect on the muscles.
Ground birch bark, fermented in sea water, is used for seasoning the woolen, hemp or linen sails and hemp rope of traditional Norwegian boats.
Many of the First Nations of North America prized the birch for its bark, which due to its light weight, flexibility, and the ease with which it could be stripped from fallen trees, was often used for the construction of strong, waterproof but lightweight canoes, bowls, and wigwams.
Birch is used as firewood due to its high calorific value per unit weight and unit volume. Birch is prized by the Sami people as it burns well, without popping, even when frozen and freshly hewn. The bark is also used in starting fires. The bark will burn very well, even when wet, because of the oils it contains. With care, the bark can be split into very thin sheets that will ignite from even the smallest of sparks.
Birches also have spiritual importance in several religions, both modern and historical.
Birch ply is made from laminations of birch veneer. It is light but strong and has many other good properties. Birch ply is used to make longboards (skateboard), giving it a strong yet flexy ride. It is also used (often in very thin grades with many laminations) for making model aircraft.
Drums are often made from Birch. Prior to the 1970s, Birch was one of the most popular drum woods. Because of the need for greater volume and midrange clarity, drums were made almost entirely from maple until recently, when advancements in live sound reinforcement and drum mics have allowed the use of Birch in high volume situations. Birch drums have a natural boost in the high and low frequencies, which allow the drums to sound fuller.
Birch wood is sometimes used as a tonewood for semi-acoustic and acoustic guitar bodies and occasionally used for solid-body guitar bodies. Birch wood is also a common material used in mallets for keyboard percussion.
Birch bark can be soaked until moist in water, and then formed into a cast for a broken arm.
The inner bark of birch can be ingested safely.
The birch tree is also New Hampshire's state tree.