A new columnar form of Betula pubescens from Finland: morphological characteristics and micropropagation

A new form of pubescent birch, Betula pubescens Ehrh. f. columnaris T. Ulvi nen f. nova found in Finland, OF, Oulunsalo, in 1992, is introduced and a d etailed morphological description including scanning electron microscopy of buds is presented. The birch is characterized by a slender growth habit du e to dense ramification and shortness of the branches. Almost all the buds on the distal branches burst and form short twigs. Some of these young shoo ts die for lack of light and space and dry up during the same summer, but t he majority are preserved, giving the tree a compact, pillar-like appearanc e. The basic cause of this deviant crown architecture is assumed to be a mu tation that leads to untimely activation of the axillary meristems, formati on of bud clusters and even proleptic branching. The birch has been cloned and has aroused interest in nurseries as a potential decorative tree.