Epicormic branching on pruned coastal Douglas-fir

Abstract

In theory, pruning is an attractive silvicultural technique because there is a great potential for increased production of clear wood after its execution. Much of the currently available literature on the pruning of Douglas-fir (Pseudotsuga menziesii) concerns the effects of pruning on diameter and height growth. Other aspects of the pruning response need to be considered, because clear wood production cannot be guaranteed merely because the trees were pruned. The Stand Management Cooperative, headquartered at the University of Washington, conducted a regional study to examine how Douglas-fir trees respond to pruning. Epicormic branching responses are reported here. Some anecdotal observations, as well as some intuitive ones, are confirmed. Epicormic branching was most severe on the south and west sides of trees. When epicormic branching was severe, sprouts occurred both at nodes (or whorls) and along internodes. Less severe or moderate sprouting tended to originate mainly in nodes. The risk of epicormic branching is minimal as long as the pruning treatment does not reduce the live crown by more than 40% and the stand has 500 or more stems/ha. The highest risk of epicormic branching was found to be when the live crown is reduced by more than 40%, and the stand carries less than 500 stems/ha.