Comparison of Paclobutrazol, Flurprimidol, and Tetcyclacis for Controlling Poinsettia Height

Growth retarding activities of paclobutrazol, flurprimidol, and tetcyclacis were compared on ‘Eckespoint C-l Red’, ‘Annette Hegg Dark Red’, and ‘Gutbier V-14 Glory’ poinsettia (Euphorbia pulcherrima Willd.). Paclobutrazol effectively controlled height of all cultivars at 0.50 mg per pot as soil drenches and at 25-50 mg°liter−1 as foliar applications. Flurprimidol soil drenches of 0.03-0.06 mg per pot and foliar sprays of 25 mg°liter−1 were equally effective in reducing plant heights of all cultivars. Tetcyclacis soil drenches and granular applications of 10-20 mg per pot provided similar reductions of plant heights on the cultivars tested. Chemical names used: α-(l-methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); (R*,R*)-(±)-β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-l,2,4-triazole-1-ethanol (paclobutrazol); and 5-(4-chlorophenyl)-3,4,5,9,10-pentaza-tetracyclo-5,4,102,6,08,11, dodeca-3, 9-diene (tetcyclacis).