ABSTRACT
Flower development was accelerated by long photoperiod. LD treatments increased stem-length, flower-diameter, and the number of double flowers. Long days accelerated stem elongation, flower initiation, and flowering time. The response to daylength depends on plant age and temperature at the onset of the illumination. Ambient temperature greatly affected the rate of flower development. Flower buds which became visible in December to January became open flowers 5 to 6 weeks later. Different lines differ greatly in their flowering time. There was no strict correlation between earliness in natural daylength and under NB treatment. Shedron and Weiler reported recently that seedlings of shasta daisy varied greatly in their requirement for flowering. Some clones of these seedlings required vernalization. Flower initiation is affected more by temperature than by daylength. These are mostly spring- and summer-flowering chrysanthemums, usually with a single row of large, white ray florets and a yellow center of disc florets.
