Birch
Silver Birch Silver Birch
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Fagales Family: Betulaceae Genus: Betula L.
Species
Many species; see text and classification

Birch is the name of any tree of the genus Betula (Bé-tu-la), 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.

The common name birch is derived from an old Germanic root similar to birka. The Proto-Germanic rune berkanan is named after the birch. The botanic name Betula is from the original Latin. Birch is used as a food plant by the larvae of a large number of Lepidoptera species, see List of Lepidoptera which feed on Birches.

The birch is considered a national tree of Russia, where it used to be worshipped as a goddess during the Green Week in early June.

Description

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, 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.^[1]

Flower and fruit

The flowers are monœcious, opening with or before the leaves and borne on three-flowered clusters in the axils of the scales of drooping or erect aments. Staminate aments are pendulous, clustered or solitary in the axils of the last leaves of the branch of the year or near the ends of the short lateral branchlets of the year. They form in early autumn and remain rigid during the winter. The scales of the staminate aments when mature are broadly ovate, rounded, yellow or orange color below the middle, dark chestnut brown at apex. Each scale bears two bractlets and three sterile flowers, each flower consisting of a sessile, membranaceous, usually two-lobed, calyx. Each calyx bears four short filaments with one-celled anthers or strictly, two filaments divided into two branches, each bearing a half-anther. Anther cells open longitudinally. The pistillate aments are erect or pendulous, solitary; terminal on the two-leaved lateral spur-like branchlets of the year. The pistillate scales are oblong-ovate, three-lobed, pale yellow green often tinged with red, becoming brown at maturity. These scales bear two or three fertile flowers, each flower consisting of a naked ovary. The ovary is compressed, two-celled, crowned with two slender stylees; the ovule is solitary.

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.^[1]

These fruit have been once used as the major food of the Incans.

Species

See also: Betula classification birch

Birches of North America include:

• Betula alleghaniensis - 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 - Virginia Round-Leaf Birch (endemic, Cressy Creek, Smyth County, Virginia)
• Betula michauxii - Newfoundland Dwarf Birch
• Betula nana - Dwarf Birch or Bog Birch (also in northern Europe and Asia)
• 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:

• 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 North America)
• Betula pendula - Silver Birch
• Betula platyphylla (Betula pendula var. platyphylla) - Siberian Silver Birch
• Betula pubescens - Downy Birch, White Birch or European White Birch (also in northern Asia)
• Betula pubescens subsp. tortuosa - Arctic White Birch (subarctic Eurasia, Greenland)
• 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

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.

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, was used as a lubricant or glue 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.

Birch leaves make a diuretic tea and to make extracts for dyes and cosmetics.

Birch twigs were bound in a bundle, also called birch, to be used for birching, a form of corporal punishment.

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 tipis.

Birch is used as firewood due to its high calorific value per unit weight and unit volume. 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 wood is used to make guitar amplifiers and speaker cabinets. They are good tonally and are also known for their sturdiness.

Birch wood is also used to make drums. They produce boosted high and low frequencies with loud low end punch that is ideal for studio recordings.

Food

In Belarus, Russia, the Baltic States, Finland, and parts of northern China, birch sap is drunk as a refreshing beverage, and is believed to have tonic qualities. It is watery and pale green in color, with a slightly sweet flavor, and is bottled commercially. Birch sap may also made into kvass. The sap of particular birch species may also be rendered into birch syrup, vinegar, birch beer (a soft drink similar to root beer), and other foods. In contrast to maple syrup, birch syrup is very difficult to produce, making it more expensive than other food syrups. It is also considerably less sweet than maple syrup and the sap for syrup production is not available until a month later than maple's. The syrup is made mainly in Alaska (from Alaska Birch) and Russia (from several species), and more rarely elsewhere.

Xylitol can also be extracted from birch, a sugar alcohol artificial sweetener, which has shown effectiveness in preventing, and in some cases repairing, tooth decay.

According to the Food Network series Unwrapped, birch is a preferred wood for the manufacture of toothpicks.

Medicinal

In northern latitudes birch is however considered to be the most important allergenic tree pollen, with an estimated 15-20% of hay fever sufferers sensitive to birch pollen grains.

The chaga mushroom is an adaptogen that grows on white birch trees, extracting the birch constituents and is used as a remedy for cancer.

The bark is high in betulin and betulinic acid, phytochemicals which have potential as pharmaceuticals, and other chemicals which show promise as industrial lubricants.

Birch bark can be soaked until moist in hot water, and then formed into a cast for a broken arm .

The inner bark of birch can be ingested safely.

References

• Flora of North America: Betula
• Flora of China: Betula
• The Monday Garden: Birches