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Mari's World Tree Expo

The Birch is a tree in the genus Betula, and together with alders, hornbeams and hazels, it forms the birch family, Betulaceae.

There are about 40 species in North American and Eurasian continents. The birch is a monoaecious tree, which means it has male and female flowers on the same tree.

The Birch is often called a pioneer tree - When the ground is cleared by a fire or any other factors, it is very quick colonizing the bare ground.

As a colonizer, the birch is happy on poor soils, and grows very rapidly in full light. Most species fruit heavily early in life and regularly. Because it has small leaves, sunlight can penetrate through its lacy foliage and reach the ground, and the birch encourages many wild plants which favor sunshine.

Among those plants are young seedlings of other trees like the oak and the beech. Although they are vulnerable in early stage of life, they can grow slowly and steadily under the protection of the birch. The birch protects the seedlings of other trees by screening direct sunlight which is sometimes too strong for young seedlings. Also with its foliage it prevents radiation cooling and its protects other plants from frost damage in winter and early spring.

However, as young trees of the oak and the beech grow taller and taller, they spread their leaves to the sun in order to catch as much sunlight as possible. With their dense foliage, the oak and the beech block sunlight. Once those trees have established themselves, the birch cannot compete with them under the dense shade.

However, you don't have to feel sorry for the birch, because normally it is tree with a short life, and by the time other long-lived trees outcompete the birch, it is fairly in the late stage of its life.

When it dies, the birch provides an excellent habitat for fungi and other small creatures, which produce the foundation of the food chain of woodland habitat. Fungi and mini beasts decompose birch wood into soil so other creatures including large trees can benefit from the enriched soils.

Now the woodland is in the stage of so-called 'climax vegetation', composed of long-lived trees and several herbacious plants like bluebells and primroses which finish all their business - growing, floweing and reproduction - by late spring before trees spread their leaves to cast a dense shade. But, when there is another fire, or when a storm or lightening let mature trees down, the sunshine once again reaches the ground, and the stage for the birch and other light-favoring plants is ready. The woodland regenerates in this way.

The Birch is a colonizer often called a pioneer tree with a short life span and and production of abundant seeds. It has a delicate and dainty appearance, which may suit its kind and generous role to nurture other trees only to be outcompeted by them. However, in fact the birch is a tree with grit. Most species are extremely hardy, tolerating very cold weather and alpine environments. They can live in colder regions and in high altitudes where other broadleaf trees and even conifers cannot survive.

The Downy Birch (above) (Betula pubescens) and the Dwarf Birch (below) (Betula nana) are among the few native trees to the arctic Iceland (I took these photos when I went to Iceland on holiday). Although growing stumped and contorted, the Downy Birch even survives in Greenland as well - next to lichens, mosses and arctic herbatious plants. On high mountains in Japan, the Erman's Birch (Betula ermanii) often forms a stand above a tree belt of conifers.

There are two native birches in Britain, the Silver Birch (Betula pendula) and the Downy Birch. Around 11,000 BC, when the last Ice Age ended, they were among the first trees to colonize Britain together with the Aspen and the Sallow.

Alan Mitchell highly values the Silver Birch for exceptional value in gardens. It grows very well on any well-drained soil but also on the less heavy clays. When taller, it provides the light shelter that is needed by other shade-preferring plants and those which may be damaged by late spring radiation frosts. The light summer foliage prevents sun-scorch of such plants.

As a native tree, it has a good relationship with native birds. The foliage in spring and in autumn carries a large population of aphids, and tits and warblers feed on them. The seeds are eaten by redpolls and siskins but also by goldfinches and blue tits.

The Silver Birch has a weeping silhouette. Its branches elegantly hang down and moves with even a subtle movement of air. When young, its bark is shiny red-brown, but with age its bark becomes white and characteristic big black diamond fissures develop. Betula pendula 'Purpurea', a cultivar of the Silver Birch, has a deep purple foliage and red leaf stalks. The bark also develops a purple tinge. I have found two trees in Caple Manor College in Enfield, north of London.

With the exception of the Beech, the Silver Birch hosts more species of fungi than any other trees in Britain. The Fly Agaric, although poisonous to animals, has a unique relationship called symbiosis with the Silver Birch. They help each other for food supply; the birch provides the fungus with sugar it produces by photosynthesis, while underground, the fungus brakes down mineral nutrients so the root system of the birch can absorb them.

As one of common trees in northern Europe, the Silver Birch, and the Downy Birch also, are associated with mythology, folklore, and traditional custom of local people. In Britain, broomsticks are traditionally made from birch twigs, which are tied around a hazel handle with strips of osier(a willow sp). Because of their suppleness, birch twigs are excellent for broomstick, but some people associate the use of birch twigs with witches. The property of delicate birch twigs which catch every subtle wind may be somehow linked with the flying tool of witches.

Although Mitchell does not highly appreciate the Downy Birch, it is ultra-hardy and undoubtedly one of the super trees in arctic countries. In Britain, it grows damper soils and is abundant in the Scottish Highlands. First its bark is red-brown as the Silver Birch, but with age it develops smooth greyish white with grey or brown horizontal bands. Unlike the Silver Birch, it never develops dark fissures, and its foliage is not pendulous.

Among introduced species is the Erman's Birch. Its native Japanese name 'dake kanba' means 'alpine birch'. It grows in high altitude, often above the tree line of conifers, and when growing in very alpine environments, it often struggles in stumped and contorted shape. In Britain, however, it seems enjoying a VIP treatment in parks and gardens under good care of gardeners and arborists. It has a shiny, pale salmon pink bark, and in one of her tree walks Letta showed us a beautiful specimen growing in Hampton Court.

The Himalayan Birch (Betula utilis), native to the Himalayas and southern China, has a variety called B.u. var. jacmontii, which is renowned for its striking snow-white bark and branches. It is often planted in parks and is also a popular street tree.

The Paper Birch (Betula papyrifera) from north America has its name from a traditional custom of native Americans who used to make a canoe from its bark. It grows across a huge area of northern North America - from Labrador to Alaska. It has a white bark with dark lenticels. When the old bark is stripped off, an pale orange surface reveals.

Letta often says that, in parks and gardens, it is suggested that birches should be planted in groups, preferably in odd numbers like 3 or 5 or more. In wild, it is difficult to find a birch growing in solitude. As a pioneer tree, the birch grow in groups to form a stand on an open ground and a mountain slope full of sunlight. Various origins of the word beith, bith or beth, variations of the Gaelic name for birch, are given as meaning 'existence', 'enduring', 'world, and 'shining one'.

REFERENCES
Alan Mitchell Collins Field Guide Trees of Britain & Northern Europe (ISBN 0 00 219213 6)
Alan Mitchell Alan Mitchell's Trees of Britain (ISBN 0 00 219972 6)
Allen J Coombes Eyewitness Handbooks TREES (ISBN 0 86318 812 5)
Oliver Rachkam The History of The Countryside (ISBN 0 75380 173 6)
Jacqueline Memory Paterson Tree Wisdom (ISBN 0 7225 3408 6)
Tatsuichi Tsujii Trees of Japan (ISBN 4 12 101238 9) (Japanese)