Chemical “pinching” of pot chrysanthemums with 2,3-dihydro-5,6-diphenyl-1,4-oxathiin

Abstract

In summer and winter experiments a research formulation of 2,3-dihydro-5,6-diphenyl-1,4-oxathiin (code name UBI-P293) was effective as a chemical “pinching”-agent on pot chrysanthemum cultivar ‘Bright Golden Anne’, when applied at 0.4 and 0.8% active ingredient to the apical region of plants within a few days of planting. A lower concentration was not so effective. When the applications were made later, they induced considerable variation in the length and quality of lateral shoots and also delayed flowering. The compound did not always prevent the development of the terminal bud, but reduced apical dominance sufficiently to permit the lateral shoots to develop normally. When P293 successfully “pinched” the plants in the winter experiment, it had no effect on the length of the lateral shoots which developed. At flowering these were too long from a commercial grower's point of view. In the summer experiment shoot length was adequately reduced by application of a foliar spray of a new quaternary ammonium growth retardant when the lateral shoots were a few centimetres long.