Pennsylvania Flower Growers #267
Poinsettias are propagated from early August through late September to keep the no. of stock plants and the propagation labor force to a mini mum. Most cultivars (cvs) require 1 to 2 weeks of long days and 8 to 10 weeks of short days to reach a 30.5 cm height at anthesis. The early propagated plants have too many weeks of vegetative growth before flower initiation and become too tall unless internode elongation is restricted. Internode elongation can be restricted by either physiological stress or chemical retardants. Growers have restricted internode elongation by withholding water and fertilizer during the early stages of vegetative growth. This method of height control is difficult to reproduce and may lead to root loss and reduction of bract expansion. Chemical retardation of poinsettias became commercially acceptable with the advent of chloromequat (Cycocel, CCC). Growers seem to prefer spraying because of the ease of application and lower cost, although some foliar phytotoxicity occurs at high concentrations. Less active ingredient is needed for spraying than for a soil drench. In 1970, Holcomb and White suggested metering chloromequat through the irrigation-fertilization system as an in expensive application method.
Keywords: Ancymidol Chloromequat (Cycocel, CCC) Internode elongation Foliar phytotoxicity withholding water