Effect of Pruning, Defoliation, and Promalin on New Shoot Development of Boxwood

Abstract

The objective of this study was to determine if summer dormancy of the boxwood species Buxus sempervirens L. ‘Suffruticosa’, B. sempervirens ‘Vardar Valley’, and B. sinica var. insularis Nakai ‘Justin Brouwers’ could be overcome by pruning, defoliation or growth regulator applications. Promalin (benzyladenine (BA) + GA 4+7) alone and in combination with pruning increased new shoot growth; however, results were not consistent across experiments. Pruning alone (shearing or tip removal) was also inconsistent in inducing new shoot growth. Defoliation (removal of leaves from new spring growth) dramatically increased new shoot development, especially when applied ten weeks after spring budbreak instead of closer to budbreak. This response was tempored by Promalin application.