Development of Ornamental Crops Under Split Night Temperatures

Abstract

Abstract Trials over five consecutive winter seasons with ornamental crops growing in the greenhouse at split night and constant night temperatures (SNTs and CNTs) showed that a 5-hr period of 17°C minimum temperature during the dark period accelerated development over a CNT minimum of 12° to 13°. Maintaining 17° from 1700-2100 HR accelerated development over a 9° to 12° minimum CNT more than later periods of a 17° minimum with Euphorbia, Hydrangea, Kalanchoe, and Lilium. Continuation of 17° until 0100 or 0200 hr before a 9° to 12° minimum CNT was adequate for flower formation in Chrysanthemum. SNTs improved the bract : stem size ratio in Euphorbia and cyme size in Hydrangea relative to a 17° minimum CNT. Begonia × hiemalis, Begonia semperflorens, Brassaia, Coleus, Fuchsia, and Impatiens showed favorable growth responses or the potential for energy savings through the use of SNTs.