BRUSHING PANSY (VIOLA TRICOLOR L.) TRANSPLANTS - A FLEXIBLE, EFFECTIVE METHOD FOR CONTROLLING PLANT SIZE

Though brushing is an effective method for controlling excessive elong ation in many species, its adoption by the commercial plug transplant industry will depend on the ease and flexibility of its application. B rushing was applied to pansy(Viola tricolor L.) seedlings growing at a density of 1500 plants m(-2) by daily stroking with 20/20 gauge netti ng. In dose response experiments, final petiole length appeared to app roach a lower asymptote as number of brush strokes increased, and the number of strokes required to give near full reduction in length incre ased under environmental conditions favouring extension growth. Ten or 20 daily strokes typically gave a 25-30% reduction in petiole elongat ion without causing plant damage or affecting subsequent flowering. Re ductions in shoot dry weight tended to parallel those for petiole leng th. Increasing the interval between strokes by up to 10 min resulted i n similar reductions as continuous brushing. There was no difference b etween brushing the plants at 09:00 or 16:00 h, or between brushing 1 or 2 times day(-1). Plants required at least 5 days treatment week(-1) for significant size control. Brushing is an effective, flexible meth od for controlling petiole length in pansy and it should find applicat ion in the commercial transplant industry. (C) 1997 Elsevier Science B .V.