Birches are medium-sized trees or large shrubs, widespread in nature in most of the temperate areas of the Northern Hemisphere; only a few dozen species belong to the genus, and very few are grown as ornamental plants in Italy; in our country there are no spontaneous birch woods, although some specimens develop in the wild at the edge of the hilly forests in the areas north of the country; in Europe they are widespread especially in the Scandinavian area.
The peculiar characteristic, which belongs to almost all species, consists of a substance, called betulin, contained in the bark, which makes it pearly white, sometimes candid. This distinctive character makes the birches very decorative, even during the winter months, when the trunks stand out in the woods, with their candid coloration, with dark, almost black marks. The foliage is deciduous, generally the leaves are bright green in color, with indented margin; the autumn color is yellow, but the dying foliage persists little on the tree, not giving a particularly lasting coloring.
The stem is erect, and in many species it can reach 25-30 m in height, while still remaining quite thin. Birches are pioneer trees, this means that their seeds sprout in an open field, away from the forest, and prepare the ground for the arrival of the seeds by the other trees, which will later form the forest; for this reason birches are not very long-lived plants.
The thin branches form a crown mostly flame-shaped, elongated, and not very dense; many cultivated varieties have pendulous branches, which give the tree a weeping appearance. The flowers are gathered in catkins, and the seeds are samare, often with thin and little highlighted wings.
Birches are part of the birch family which includes some of the most famous plants with catkins including hazelnuts, alders and hornbeam trees.
This family is made up of 6 genera and in total more than 160 species of deciduous trees and bushes that grow, generally in the temperate-northern regions. The whole family is characterized by alternate leaves and flowers in separate catkins of which only the males are well evident and decorative.
The genre betula it includes from 30 to 60 species: trees not very long-lived and considered pioneers in the whole Northern hemisphere.
Its name derives from the Gallic and is a diminutive of "betua". The Germanic name birch, on the other hand, has an Indo-European origin and probably means "shining".