INFLUENCE OF URBAN WASTE COMPOST MEDIA AND PACLOBUTRAZOL DRENCHES ON IMPATIENS GROWTH

Bedding plant growers have the opportunity to utilize urban waste comp ost in their growing media, but variation in substrates that constitut e the compost could influence the efficacy of growth regulator drenche s, This experiment investigated the effect of 0%, 30%, 60%, and 100% c ompost made from biosolids and yard trimmings on the efficacy of a pac lobutrazol drench on Impatiens wallerana Hook.f. 'Accent Red'. Paclobu trazol was applied at a,i. drench rates of 0, 0.016, 0.032, 0.060, or 0.125 mg/pot. Growth of control plants (0 mg) increased linearly as th e percentage of compost in the medium increased from 0% to 100%. Growt h of plants in all media decreased as paclobutrazol concentration incr eased to approximate to 0.016 mg with no further decreases at higher c oncentrations. The efficacy of paclobutrazol varied with the medium. F or example, paclobutrazol at 0.016 mg reduced shoot: dry mass by 31% r elative to control plants in the presence of 100% compost but only 17% in the absence of compost. The percentage of growth reduction, relati ve to control plants, increased as the percentage of compost in the me dium increased. Chemical name used: pha(1,1-dimethylethyl)-1H-1,2,4-tr iazole-1-ethanol (paclobutrazol).