Growth of Betula pendula Roth. the first season after transplanting at two phenological stages

The root extension rate of Betula pendula, transplanted at two phenological stages, was studied in a Nordic climate. Landscape-size trees were transplanted from the field into root-study boxes (rhizotron) in early and late spring of 1999 and 2000. In early spring, 6 trees were transplanted when the leaves had just started to unfold; likewise, in late spring, six trees were transplanted when the leaves were fully unfolded and the shoot extension was in progress. Root growth was recorded during the first post-transplant season and the tree roots were finally excavated. Results indicate that the root extension rate of B. pendula follows seasonal soil temperature. The mean root extension rates at ten days intervals varied from 4 to 11 mm/day with a total average for the growing season of 7 mm/day in 1999 and varied from 4 to 9 mm/day with a total average for the growing season of 4 mm/day for 2000. The average length of new roots was 89 cm and there was no significant difference in length, dry weight or number of new roots between the two transplant times. It appears, therefore, that the phenological stage at transplanting during the period from bud break to fully developed leaves has minor effect on landscape establishment of B. pendula, when an adequate amount of water is provided.