Abstract
In the present experiments, three items on flowering in dahlia were studied separately.
1. Effects of phtoperiod prior to decapitation on the growth rate and flowering of the lateral shoots:
When plants were grown under the day-length of 13-hours (the optimum photoperiod) after decapitation, the photoperiods given before the decapitation had no effect on the growth rate and flowering of the lateral shoots. When the plants decapitated were exposed to the photoperiods shorter than the lower critical length (12 hours), marked effect of short day-length given before decapitation on retardation of budding or flowering was observed.
Photoperiod given to the plants before the decapitation did not affect the number of florets per flower head.
2. Effects of the size of cutting upon rooting, growth rate and flowering:
Cuttings rooted well without reference to their size. The larger plants flowered earlier and more simultaneously than the smaller ones. A plant propagated from the cutting of 5g or more seems to be useable in commercial production of cut-flowers.
3. On the propagating method:
The plants propagated from crown-tubers required longer photoperiod for normal flowering than those propagated by cuttings. Some of the flower buds formed in the plants with crown-tubers remained blind under 13-hour days.
