The paper birch is the North American equivalent of the Finnish downy birch (B. pubescens), growing in both mono-specific and mixed forests up to the timberline in the north. Though closely resembling the downy birch in appearance, it is of less refined habit, with larger and more oval leaves. The name comes from the pale bark which exfoliates in papery sheets and rolls up like papyrus scrolls. The shade of the bark varies depending on origin, and those favoured for planting have white, unblemished bark.
Although silver birch (B. pendula) has become very popular, to the extent that it has even been called Finland’s national tree, in their own local environment at least as many Finns have come across the white or downy birch, familiar but largely unknown.
Curly birch (or visa birch) is a genetic variety of the silver birch (Betula pendula). Its wood has curled grain, called "visa" formation in Finnish, an unusual growth form. At various places on the trunk and branches the bark is noticeably thicker than usual, and parts of the bark appear within the wood itself as brown spots or streaks. The wood is very decorative, at best resembling wooden marble.
The Japanese white birch is the equivalent of the native Finnish species, B. pendula, called white or silver birch. Many experts consider the two as different forms rather than different species. There are distinguishing characteristics: the Japanese tree has larger leaves, there is no droop to the branches, and the bark doesn’t develop like that of the Finnish species, but rather maintains its handsome whiteness into maturity, sometimes with a touch of pink.
Voted Finland’s national tree in 1988, the silver birch has a special position in the Finnish landscape owing to its pale greenness and in winter to its graphically sharp silhouette. It is also a part of the Finnish mindscape: the story “The birch and the star” by Topelius is familiar to most Finns, and local drama groups and summer festivals typically use silver birch as part of the scenery.
This shrub is one of those which, in addition to the dwarf birch B. nana, make up the sub-genus of dwarf birches. However, it grows larger than B. nana, to about 2 metres. The bark is greyish-white and the branches red-brown. The leaves are small and more oval than in B. nana. The catkins are fairly thick and erect, the females becoming fuzzy seed catkins after pollination.
Erman’s birch is found over a large range in the northern parts of north-east Asia. It is very variable in form: the Japanese and Korean mountain form resembles that of the shrubby mountain birch (B. pubescens subsp. czerepanovii) found in northern Finland, while the Sakhalin Island form, for example, is that of an upright large tree. In places it forms large economically valuable forests, the wood being very hard.
This large handsome birch can reach 30m with a trunk 1 metre in diameter in its native habitat in the Far East. It is used there in plywood and by the furniture industry but is also a beautiful park tree. The leaves are slender, long and oval, and the branches droop attractively. The bark varies from white to cream, silvery or even pale red, exfoliating showily from the trunk and large branches in broad strips. In old age the bark becomes impressively thick.
The bark and shoots of yellow birch give off a strong smell of wintergreen when rubbed or crushed. The trunk is yellowish or silver-grey, without much tendency to peeling. The long leaves are noticeably larger than either of the two Finnish species, and resemble hornbeam (Carpinus) leaves, lying along the branches in layers. This is a showy species, especially in its autumn colour, when it gleams in the sunshine like a raised group of yellow azalea.