Watsonias as container plants: using paclobutrazol for flowering and height control

Abstract

South African watsonias were evaluated for their potential as flowering pot plants, following chemical dwarfing. Corms were treated with paclobutrazol as a 5mg, 10mg or 20mg active ingredient (a.i.) per pot post-emergent soil drench, or vacuum-infiltrated pre-planting with 0.5mg, 1mg or 2mg a.i. per corm. Both treatments significantly reduced perpendicular leaf height, although infiltration of all but the most under-developed corms caused inflorescence abortion. Flowering plants shorter than 36cm were considered to be attractive, commercially viable pot plants — provided that flowering percentage, flower number and the onset of flowering were not adversely affected by treatment and that flowers were displayed clear of the foliage. The highest concentration of paclobutrazol applied as a drench resulted in obscured inflorescences, indicating an enhanced dwarfing effect on the inflorescence rather than leaf heights. Marketable dwarfs were obtained following a single drench treatment of 10mg a.i. per pot or after a single infiltration episode with 1mg a.i. per corm, allowing the successful adaptation of watsonias to container cultivation.