Many species;
see text and classification
Birch is the name of any tree of the genus Betula, in the family Betulaceae, closely related to the beech/oak family, Fagaceae. These are generally small to medium-size trees or shrubs, mostly of northern temperate climates. The simple leaves may be toothed or lobed. The fruit is a small samara, although the wings may be obscure in some species. They differ from the alders (Alnus, the 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.
Birch is a food plant for a number of species of Lepidoptera including Oak Hook-tip, Large Emerald, Common Emerald, Common Marbled Carpet, November Moth, Autumnal Moth, Purple Thorn, Scalloped Hazel, Feathered Thorn and Dotted Border.
Species
- Birches of North America include
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- Betula allegheniensis - Yellow Birch (B. lutea)
- Betula cordifolia - Mountain Paper Birch
- Betula glandulosa - American Dwarf Birch
- Betula lenta - Sweet Birch, Cherry Birch, or Black Birch
- Betula lenta subsp. uber - Cherry Creek Birch (endemic, Cherry Creek, Smythe Co., VA)
- Betula michauxii - Newfoundland Dwarf Birch
- Betula neoalaskana - Alaska Birch or Yukon Birch
- Betula nigra - River Birch or Black Birch
- Betula occidentalis - Water Birch or Red Birch (B. fontinalis)
- Betula papyrifera - Paper Birch, Canoe Birch or American White Birch
- Betula populifolia - Gray Birch
- Betula pumila - Swamp Birch
- Birches of Europe and Asia include
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- Betula albosinensis - Chinese Red Birch
- Betula albosinensis var. septentrionalis - North Chinese Red Birch
- Betula alnoides - Alder-leaf Birch
- Betula austrosinensis - South China Birch
- Betula chinensis - Chinese Dwarf Birch
- Betula ermanii - Erman's Birch
- Betula grossa - Japanese Cherry Birch
- Betula jacquemontii (Betula utilis subsp. jacquemontii) - White-barked Himalayan Birch
- Betula mandschurica - Manchurian Birch
- Betula mandschurica var. japonica - Japanese Birch
- Betula maximowiczii - Monarch Birch
- Betula medwediewii - Caucasian Birch
- Betula nana - Dwarf Birch (also in northern Asia)
- Betula pendula - Silver Birch
- Betula platyphylla (Betula pendula var. platyphylla) - Siberian Silver Birch
- Betula pubescens - White Birch, European White Birch or Downy Birch (also in northern Asia)
- Betula szechuanica (Betula pendula var. szechuanica) - Sichuan Birch
- Betula utilis - Himalayan Birch
- Note: many American texts have B. pendula and B. pubescens confused, though they are distinct species with different chromosome numbers
Uses
Birches are versatile trees, used for many purposes. The sap, bark, leaves, wood, twigs, and roots are used for food, construction materials, medicinal treatments, lubricants, and other practical applications.
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, extracted from birch bark, was used as a lubricant and for medicinal purposes.
Birch leaves are used to make a diuretic tea and to make extracts for dyes and other purposes. Birch sap is drunk as a tonic or rendered into birch syrup, vinegar, beer, soft drinks, and other foods.
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 trees, was often used for the construction of strong, waterproof but light-weight canoes. The bark is high in betulin and betulinic acid, phytochemicals which have potential as pharmaceuticals, and other chemicals which show promise as industrial lubricants.
Birches also have spiritual importance in several religions, both modern and historical.
See also
External links
