Hairy Birch

Betula pubescens

Hairy birch can be told apart from Silver birch by its downy twigs, which lack the little warts found on those of its smooth-twigged relation. Its bark, though white, is less shiny and is more apt to peel away in strips. On the whole it is a smaller tree, with more upright branches, and its general aspect is well shown in the view of a Highland birchwood (Plate 10). It is a common wild tree in the north and west of Britain, where it frequendy grows on damp, peaty moorlands. Its leaves have only a single series of teeth. Other fine points of difference are shown in the sketches. Bark shows grey horizontal bands.

You may of course come across individual trees that show intermediate characters: these are usually hybrids.

The timbers of both the birches are much alike, but neither is of mudi commercial value in Britain. In Scandinavia where trees of better form and larger si2e are common, the wood is widely used for furniture and for peeling the veneers that are used in birch-surfaced plywood. Our smaller trees yield a good deal of turnery wood, which is made into broom heads, tool handles, and small wooden objects of many kinds. Birch wood is pale brown in colour, with a dull surface, and is both hard and strong; it is not durable out of doors, but lasts well if kept dry. It is a first-rate firewood, and still provides most of the winter fuel for farms in Scandinavia and amid the Alps.

Many uses have been found for birch twigs, but none is important commercially today. They have been used for sweeping brooms, steeplechase jumps, and for 'birching' unruly schoolboys. They make good firelighters, and also - when barked - useful whisks for beating-up sauces. £irch bark is waterproof, and sheets of it have been used for roofing woodland shelters. The tougher bark of the Canadian Paper birch, B.papyrifera, which can be peeled away in large sheets, is used by the Indians for making strong, light canoes.

Birch Trees Winter

Birches are typical 'pioneer1 trees, able to invade bare land and colonise it successfully. They are quick to appear without planting, wherever woods are felled and left to nature, and they readily spring up on commons where regular grazing has ceased and especially after fires. But birches, as trees go. are not long-lived, and the usual course of events is that they are gradually replaced by other 'successor1 trees, such as oaks and beeches, that have grown up in their shelter. Sixty years is a good age for a mature birch; an oak or a beech will often stand for two centuries.

Birches are often attacked by the harmful wood-rotting fungus Polyporus betuhn us which bears bracket-shaped sporophores on the sides of their trunks. These brackets do not develop until the decay is far advanced, and it is then too late to save the tree - or even its timber.

Another fungus often associated with birch is the Fly agaric Amanita muscaria, This is a bright red toadstool with white spots; it is poisonous, but luckily its appearance is so striking that it cannot be confused with mushrooms or other edible fungi. The Fly agaric does no harm at all to the tree, but lives in a symbiotic association with its roots; it draws certain nutrients from the tree's sap stream, and supplies others in return,

A third species of birch, not illustrated here, is found locally in the Scottish Highlands. This is the Dwarf birch B. nana, which seldom becomes bigger than a shrub. It is one of the world's hardiest plants, able to flourish on the tundras around the Arctic Circle. You can identify it by its small round leaves, which are edged with rounded lobes, rather than teeth, and also by its shorter, upright and bushy branches.

figure 20

Flowering twig of hairy birch in April, with female catkins along its sides, male catkins at its tip (life size).

Left above; dichasium of three female flowers (X20).

Left below: dichasium of three male flowers (x20).

Irch Tree Leaves

figure

Leafy twigs, fruiting catkins, seeds and bracts of birches in October. Left Silver birch (life site) Below: Hairy birch (life size). Below left: seed and fruit bract of Silver birch (X5). Below right seed and fruit bract of Hairy birch (X51-

Betula Pubescens Bracts
+1 0

Post a comment