Forcing Pieris japonica ‘Debutante’

Abstract It was investigated whether Pieris japonica ‘Debutante’, cultivated as a potplant, can be forced before Christmas. To achieve this, early flower bud formation is required. Flower bud formation has an optimum temperature of approximately 17 °C. Short days, applied when the shoots have grown out sufficiently, promote flower bud formation. Young plants, potted in spring, form flower buds less readily than older plants that have not been repotted in spring. The growth retardant daminozide improves flower bud formation. Flower buds become dormant after their formation, but endodormancy can be broken in October–November by chilling and application of gibberellic acid. After breaking dormancy plants can be forced in a greenhouse at about 22 °C with high intensity supplemental lighting for 12 h during the daytime.