Micropropagation of birch

Abstract

The genus Betula probably has its origin in the NE of Asia and consists of about 60 species [20]. The birch species are widely distributed over the Northern Hemisphere, but they are limited to the temperate and arctic zones. According to Regel [32], two groups can be distinguished; Eubetula and Betulaster. The latter group consist of a few species mainly found in Japan and in the SW and the middle of China. The Eubetula group is divided in to three sub-groups, Costatae Regel (yellow birches), Albae Regel (white birches) which are tree forms, and Nanae Regel representing bush and dwarf forms. The yellow birches grow wild only in North America and in Asia, whereas the white birches are distributed throughout Europe, Asia and North America. Four birch species are native to Europe. Two of them — Betula pendula (Roth) and Betula pubescens (Ehrh) — are tree forms and the others — Betula nana (L) and Betula humulis (Schrank) — are bush forms. The birch species are well known for their peculiar bark, striking trunks and graceful branches, which make them valuable as garden trees.