The Relationship of Vegetative Maturity to Rest Development and Spring Bud-break1

Abstract

Abstract Rest period, the transition between summer and winter dormancy, and vegetative maturity were studied in red-osier dogwood (Cornus stolonifera Michx.) in Oregon. Maximum rest occurred in late October and early November when 180 days were required for growth resumption under favorable growing conditions. The transition between summer dormancy (correlative inhibition of lateral buds) and winter dormancy (onset of rest) occurred in early September, 21 days before maturity, 49 days before natural leaf abscission, and 56 days before maximum rest. Lateral buds of plants defoliated prior to this transition grew within 10 days while buds of plants defoliated after that date did not resume growth until spring. Vegetative maturity was achieved in late September. Plants defoliated after that time overwintered without apparent injury. Spring regrowth was normal in mature plants, but bud-break was delayed as much as 10 days as a result of defoliation the previous autumn. Vegetatively immature plants defoliated before late September died outright or sustained varying degrees of stem dieback. Natural leaf abscission occurred in late October, 49 days after plants were vegetatively mature. The extent of stem dieback was inversely related to stage of maturity, a relationship that provides a useful means of quantitatively expressing when, and to what extent, plants are mature.