Terminal Bud Cluster Pruning Promotes Apical Control in Transplanted Shade Tree Whips

Abstract

Transplant-induced loss of apical control, as measured by the central leader to total lateral branch caliper ratio, was documented for 'Patmore' green ash (Fraxinus pennsylvanica) and 'Autumn Purple' white ash (F. americana) by measuring trees one, two, five and 10 years after transplanting. For both species, the central leader to total lateral branch caliper ratio ranged from 0.3 to 0.5, regardless of the age from transplanting, indicating that large lower limb development (loss of apical control) was initiated at transplanting and persists for up to 10 years. Transplanted nursery grown 'Patmore green ash and 'Autumn Purple' white ash trees bud pruned to maintain a strong central leader had central leader to total lateral branch caliper ratios of 0.7 and 0.8, respectively. A pruning treatment, removing the lateral buds from the terminal bud cluster, reduced large lower limb development, maintained apical control and resulted in better lateral branch distribution in transplanted red oak {Quercus rubra) and 'Patmore' and 'Autumn Purple' ash whips than leaving the terminal bud cluster intact.