Ornamental Cabbage and Kale Growth Responses to Daminozide, Paclobutrazol, and Uniconazole

Abstract

Ornamental cabbage and kale (Brassica oleracea var. acephala) plants of cultivars Osaka White and Nagoya Red were treated with paclobutrazol and uniconazole as foliar sprays or substrate drenches. These treatments were compared to the industry standard of daminozide foliar sprays. Applying drenches of paclobutrazol (a.i.) at 4 mg/pot or uniconazole (a.i.) at 1 mg/pot (28,350 mg = 1.0 oz) resulted in 6% or 17%, respectively, shorter `Osaka White' plants while a 2 mg/pot paclobutrazol drench or a uniconazole drench at 0.25 mg/pot resulted in 25% shorter `Nagoya Red' plants. Although effective, the expense of substrate drenches for both plant growth regulators (PGRs) would not be economically feasible for growers to use. Paclobutrazol foliar sprays at concentrations of up to 80 mg·L-1 (ppm) were ineffective in controlling plant height and diameter of either `Osaka White' or `Nagoya Red'. A uniconazole foliar spray of 16 mg·L-1 resulted in 17% shorter `Nagoya Red' plants and 6% shorter `Osaka White' plants. A daminozide foliar spray of 2500 mg·L-1, sprayed twice, resulted in 21% shorter plants for both cultivars. Spraying daminozide would provide optimal height control for the retail grower. Although spraying daminozide twice controlled plant height and costs half the amount of an uniconazole spray at 16 mg·L-1, plant diameter was not affected with daminozide, therefore a wholesale grower who would desire a smaller diameter plant should use a uniconazole spray of 16 mg·L-1.