EFFECTS OF HUMIDITY ON THE GROWTH AND FLOWERING OF CUT-FLOWER CHRYSANTHEMUMS (DENDRANTHEMA-GRANDIFLORA TZVELEV)

Four discrete and continuous humidity treatments (0.1, 0.4, 0.7 and 1. 1 kPa vapour pressure deficit) were applied to plants of three chrysan themum cultivars (Snowdon, Pink Gin and Snapper) growing in daylit, co ntrolled environment cabinets in autumn and spring experiments to dete rmine effects on growth and flowering. There was some reduction in tot al leaf area and leaf dry weight in the highest humidity treatment but , overall, effects on stem and leaf growth were slight. Effects of hig h humidity on flowering were more marked, with estimated maximum delay s of 4-5 d in flower development and reductions in flower dry weight a t 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 en vironmental variable is of major consequence in commercial growing dur ing the winter period.