Effects of humidity on the growth and flowering of cut-flower chrysanthemums (Dendranthema grandifloraTzvelev)

SummaryFour discrete and continuous humidity treatments (0.1, 0.4, 0.7 and 1.1 kPa vapour pressure deficit) were applied to plants of three chrysanthemum cultivars (Snowdon, Pink Gin and Snapper) growing in daylit, controlled environment cabinets in autumn and spring experiments to determine effects on growth and flowering. There was some reduction in total leaf area and leaf dry weight in the highest humidity treatment but, overall, effects on stem and leaf growth were slight. Effects of high humidity on flowering were more marked, with estimated maximum delays of 4–5 d in flower development and reductions in flower dry weight at harvest. Visual appearance was not impaired in any of the treatments. It was concluded that the chrysanthemum is relatively insensitive to humidity within the range tested and that it is unlikely that this environmental variable is of major consequence in commercial growing during the winter period.