The Effect of Climatic Conditions on Dormancy Development of Peach Buds. I. Temperature1

With controlled temperatures low temperature efficiency in releasing peach buds from dormancy follows an optimum curve in which 6°C is the optimum for average lateral leaf buds and 10°C is about half as efficient. “Weighted chilling hours” instead of “chilling hours” was proposed as a chilling measurement criterion. A high temp of 21°C, when alternated daily with low temp, nullified the low temp effect; a high of 18°C had no effect. Interrupting the chilling by 2 separate periods of 11 and 12 days at 20°C did not show any nullifying effect, but greatly enhanced lateral leaf bud break.