Silver birch

Appearance

It is a medium-sized deciduous tree, typically reaching 15–25 metres tall ), with a slender trunk usually under 40 centimetres diameter, but exceptionally to 1 metre diameter, and a crown of arched branches with drooping branchlets. The bark is white, often with black diamond-shaped marks or larger patches, particularly at the base. The shoots are rough with small warts, and hairless, and the leaves 3–7 centimetres long, triangular with a broad base and pointed tip, and coarsely double-toothed serrated margins. The flowers are wind-pollinated catkins, produced before the leaves in early spring, the small 1-2mm winged seeds ripening in late summer on pendulous, cylindrical catkins 2–4 centimetres long and 7 mm broad.

Habitat

''B. pendula'' commonly grows with the mycorrhizal fungus ''Amanita muscaria'' in a mutualistic relationship. This applies particularly to acidic or nutrient poor soils. Other mycorrhizal associates include ''Leccinum scabrum'' and ''Cantharellus cibarius''. Old trees are often killed by the decay fungus ''Piptoporus betulinus'', and the branches often have witch's brooms caused by the fungus ''Taphrina betulina''.

Uses

Silver birch is often planted in parks and gardens, grown for its white bark and gracefully drooping shoots, sometimes even in warmer-than-optimum places such as Los Angeles and Sydney. In Scandinavia and other regions of northern Europe, it is grown for forest products such as lumber and pulp, as well as for aesthetic purposes and ecosystem services. It is sometimes used as a pioneer and nurse tree elsewhere. It is naturalised and locally invasive in parts of Canada. Birch brushwood is used for racecourse jumps, and the sap contains around 1% sugars and can be drunk or be brewed into a "wine". Historically, the bark was used for tanning. Silver birch wood can make excellent timber for carving kitchen utensils such as wooden spoons and spatulas: its very mild, sweet flavour does not contaminate food, and it has an attractive pale colour. Bark can be heated and the resin collected; the resin is an excellent waterproof glue and firestarter.

Successful birch cultivation requires a climate cool enough for at least the occasional winter snowfall. As they are shallow-rooted, they may require water during dry periods. They grow best in full sun planted in deep, well-drained soil.

Cultural

Silver Birch is Finland's national tree. Occasionally one uses leafy, fragrant boughs of Silver Birch to gently beat oneself in a sauna. The boughs are called vihta or vasta. This has a relaxing effect on the muscles.

In Sweden, the bark of birch trees was ground up and used to make bark bread, a form of famine food. The removal of bark was at one time so widespread that Carl Linnaeus expressed his concern for the survival of the woodlands.