Ethephon-induced Defoliation and Delay of Spring Growth in Cornus stolonifera Michx.1

The effectiveness of (2 chloroethyl)phosphonic acid (ethephon) in inducing defoliation and in delaying spring bud growth of red-osier dogwood was related to the time of application. Plants treated with ethephon before they matured were not effectively defoliated. Mature plants were effectively defoliated and ethephon’s effectiveness increased progressively at subsequent treatment dates. Ethephon treatments applied on September 29, October 6 and 13, delayed spring bud break by 7, 5, and 3 days respectively. Hand defoliation on the same dates induced identical delays in spring growth.