ABSTRACT
Distributed within the northern hemisphere, birches are important ecologically for forestry and as amenity trees. Horticultural interest for amenity purposes is for bark effect, elegant growth habit and attractive foliage; many have handsome catkins and good autumn colour. Taxonomic revisions of this genus have identified 4 subgenera, 8 sections and 2 subsections. The major group containing most of the known species and hybrids of interest to grafters are found in subgenus Betula; with section Betula containing the so-called white and silver bark birches. In the subgenus Nipponobetula, attempts at grafting B. corylifera failed in the 1960s, possibly due to incompatibility. Comparisons have been made between successful takes of Birch grafts on well-established potted rootstocks grown for a full season with others severely root pruned and potted in the autumn prior to grafting in February. During late winter, Birch trees are particularly liable to ‘bleed’ when shoots are pruned to supply scion wood for winter grafting.
