The Effect of Cooling Method, Age and Season on Amount and Quality of Greenhouse Roses

Abstract

Rose flowers produced in greenhouses during the summer in Israel have short thin stems carrying small buds with pale petioles. Experiments were conducted to examine whether cooling can improve flower quality. During the first part of the summer when flower quality and later quantity also decreased, cooling treatments had no significant beneficial effects. Still night cooling with an air conditioner improved quantity and quality. During the second part of the summer. most of the cooling methods increased yield and later quality. Quality and quantity loss during the first part of the summer. are the conjectural results of the high number of flowers that developed on the plants and of their fast growth, which apparently created a vigor sink and a deficiency of the carbohydrate supply. The hypothesis is that the improved carbon balance produced by cooling during the first part of the summer, was spread over a large number of growing stems and therefore was too weak. With fewer flowers during the second part of the summer available carbon could contribute more to each flower.