Abstract
Bulbs of ‘Casablanca’ produced in Holland and stored at temperatures below freezing were purchased from a commercial stock in mid-August. They were divided into groups of 20 bulbs and restored at −1.5~−2.0°C before use. They were subjected to different temperatures for various durations to allow rooting and sprouting in a plastic container filled with wet peat moss and thereafter planted and grown in a plastic house maintained at min. 14°C. Cut flowers with good quality were obtained when bulbs were subjected to 2°C for 3~4 weeks, at 5 and 8°C for 2~3 weeks or at 12°C for 2 weeks before planting.
Bulbs were planted in the house at different dates from 1 September to 1 December after being subjected to 12°C for 2 weeks to allow rooting and sprouting. As planting was delayed, the number of flowers decreased and the number of plants with nodes that had no differentiated flowers on the upper part of the main peduncle increased. Moreover, necrosis was observed in the tips of the leaves on the middle to upper part of all plants planted on and after 31 October.
Observation under the microscope revealed that flowers developed normally and reached an outer stamen formed stage in the planting of September, whereas some flowers did not initiate and the tips of some leaves became transparent in the November plantings.
