Brushing pansy (Viola tricolor L.) transplants: a flexible, effective method for controlling plant size

Though brushing is an effective method for controlling excessive elongation in many species, its adoption by the commercial plug transplant industry will depend on the ease and flexibility of its application. Brushing was applied to pansy (Viola tricolor L.) seedlings growing at a density of 1500 plants m-2 by daily stroking with 20/20 gauge netting. In dose response experiments, final petiole length appeared to approach a lower asymptote as number of brush strokes increased, and the number of strokes required to give near full reduction in length increased under environmental conditions favouring extension growth. Ten or 20 daily strokes, typically gave a 25-30% reduction in petiole elongation without causing plant damage or affecting subsequent flowering. Reductions in shoot dry weight tended to parallel those for petiole length. Increasing the interval between strokes by up to 10 rain resulted in similar reductions as continuous brushing. There was no difference between brushing the plants at 09:00 or 16:00 h, or between brushing 1 or 2 times day I. Plants required at least 5 days treatment weekfor significant size control. Brushing is an effective, flexible method for controlling petiole length in pansy and it should find application in the commercial transplant industry.