Flowering in florists c̓ineraria, Senecio cruentus, as influenced by gibberellin, light, and temperature

Various treatments were used to manipulate the flowering of the florists' cineraria, Senecio cruentus DC. 'Hansa' and 'Stellata* for the ultimate purpose of raising the cineraria as a cut flower. Various light intensities and temperatures were used to understand better the flowering process in the cineraria. Gibberellin was applied in an attempt to initiate flowering without the required cold induction, to hasten flowering, and to elongate the floral stems. Neither GA₃ nor GA₇ significantly hastened flowering of the cultivars Hansa and Stellata grown under various cultural conditions, with one exception. When applied twice weekly as a 10-ppm spray after a six-week cold induction (4.5-7.0° C), the gibberellins did hasten flowering of Stellata plants. Both gibberellins significantly increased stem length. Floral buds appeared at the same time whether Hansa plants were vernalized (10-13° C) for four weeks or for six weeks. A two-week cold induction, low light intensity (25- 80 foot-candles), or warm temperatures (minimum 15° C) delayed floral development. Floral initiation was observed histologically as early as two weeks after the start of cold induction (15.7° C days, 9° C nights in Hansa plants. Most of these showed floral primordia four to six weeks after inductive treatments were begun. The later Hansa plants were vernalized, the earlier after cold induction (15.7° C days, 9° C nights) floral buds appeared. However, total flowering time from sowing tended to increase as vernalization was delayed. Earliest floral development occurred in plants that were vernalized beginning six weeks after sowing.