Experiments with Growth Retardants on Dahlia

B-Nine proved very effective in retarding the height of Dahlia and developing well-shaped plants in pots. Among the three concentrations viz., 2,500 5,000 and 10,000 ppm, the highest concentration caused maximum retardation. Two foliar applications at the vegetative stage showed greater inhibition of plant height than treatment at other stages of growth. B-Nine at 10,000 ppm markedly suppressed the height of 15 varieties of Dahlia and the percentage of retardation varied from 17.4 to 64.7, compared to the height of control plants. The leaves of the treated plants were smaller in size, stiffer and darker green in colour. Treatment with B-Nine also improved the size of the flower, increased the number of florets and the flower remained fresh for a longer period on short and stout stalk. The retardant was also effeative in suppressing the height of pinched plants.

Treatment with lower concentrations of CCC (1,000,2000) as foliar spray or soil drench, in most cases, promoted the height of plants by 0.6 to 12.0 per cent, while retardation due to the higher concentrations (4000, 8000 ppm) varied from 1.5 to 12.6 per cent in the different varieties.