Tree a Week: Birch

Interesting Facts

  • Birch is in the genus Betula. The birch family Betulaceae contains six genera of deciduous nut bearing trees including birches, alders, hazels, horn beams and hop-hornbeams.
  • There are about 40 species of small to medium trees and shrubs, in Northern temperate climates
  • Average lifespan of the birch is 40-50 years. In favourable conditions, it can live for as long as 200 years.
  • The bark contains high levels of oil which helps it to catch fire even if it is wet. It also prevents the bark from decomposing, even if the remaining part of the tree (wood) is rotten.
  • Most birches, except for Paper birch and River birch need low pH soils for a healthy growth.
  • The word birch is thought to have derived from the Sanskrit word ‘bhurga’ meaning a ‘tree whose bark is used to write upon’.
Birch distribution

Ecological Function

They are regarded as pioneer species, rapidly colonising open ground especially following a disturbance or fire. The short lifespan of birch lays down decomposing wood for the next species in line in a forest succession. Birches are generally lowland species and are “opportunists in steady-state woodland systems”.

Fungal Relationships

Mycorrhizal fungi (in symbiotic relationships with parent trees) includes amanita muscaria, birch bolete and chanterelles. Saprophytic (eat dead trees) and parasitic fungi include birch polypore (pictured above) which has multiple medicinal uses including anti-bacterial, anti-viral properties and able to reduce certain cancer cells by 90%. Tinder fungus is a good one to know if you’re out in the forest since it catches alight so readily.

Identification

Bark: The bark of all birches characteristically is marked with long horizontal lenticels, and often separates into thin papery plates. Its colour gives the common names red birch, white birch, black birch, yellow birch, gray birch, and silver birch to various species.

Leaves: The leaves of the different species vary but little. All are alternate, doubly serrate and feather-veined. 

Uses

The sap, bark, leaves, wood, twigs, and roots are used for food, construction materials, drums, medicinal treatments, lubricants, and other practical applications. For example, birch can be used to make printing paper; commercial oil of wintergreen (methyl salicylate closely related to aspirin)  was made from the sweet birch (Betula lenta); and leaf extracts have been used for dyes and cosmetics. The inner bark of birch can be used as flour like substitue and the birch fruit once served as the major food of the Incas.


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.
The birch sap is used as a substitute for sugar in Lapland and Sweden, and Alaskan birch is used to create syrup similar to maple. The sap is used to make beer and wine in the Northern Europe, Russia and China .

Branch and leaf tips can be eaten. The leaves produce a pleasant tea and an infused oil and is an excellent detoxifier, mainly working on the urinary system to remove waste such as kidney or bladder stone, gravel, gout, and rheumatism. It reduces fluid retention and swellings, and clears up many skin problems.

We now know from archaeological evidence that birch resin or tar has been used as glue for 80,000 years. It is extracted from the bark and remains waterproof and not brittle.

For Further Reading

If you want to know more about trees, particularly in the context of creating a forest garden, this book by Martin Crawford is worth checking out. It’s pretty affordable for a thick comprehensive book full of quality photographs and a lifetime’s worth of research and expertise from a man who has been at the forefront of forest gardening for the last 20 years.

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