COMPARISON OF PACLOBUTRAZOL DRENCH AND SPIKE APPLICATIONS FOR HEIGHT CONTROL OF POTTED FLORICULTURE CROPS

Experiments with 'White Christmas' and 'Carolyn Wharton' caladiums (Caladium xhortulanum Birdsey), croton (Codiaeum variegatum), brassaia (Brassaia actinophylla Endl.), 'Annette Hegg Dark Red' poinsettia (Euphorbia pulcherrima Willd.), and 'Super Elfin Red' and 'Show Stopper' impatiens [Impatiens wallerana (L.) Hook.f.] determined effectiveness of paclobutrazol in solid spike form as compared to media drench applications for height control. Paclobutrazol drenches and spikes were effective for all crops tested, with a similar concentration response for all, except that drenches had greater efficacy than spikes on caladium. A reduced effect was observed when spikes were placed on the medium surface of 'Super Elfin Red' impatiens, while placement in the middle of the pot or around the side was equally effective. These results indicate that the spike formulation of paclobutrazol has potential to provide adequate size control for floriculture crops with the possible exception of rapidly developing crops, such as caladiums. Chemical name used: (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazol-1-yl-)penten-3-ol (paclobutrazol).