VEGETATIVE AND FLOWERING RESPONSES OF LILIUM LONGIFLORUM THUNB. CULTIVARS TO COLD AND LONG DAY TREATMENT AS RELATED TO BULB MATURITY
Bulbs of L. longiflorum 'Croft', 'Ace' and 'Nellie White', harvested monthly from July to October 1968 and 1969, were grown continuously at non-inductive temperatures (above 22°C) after various lengths of dark storage at 4.5°, 10° and 15.5°C. Half were grown under short day (9 hrs, SD), and the other half under long day conditions (16 hrs, LD). The later the harvest the earlier the emergence, and cold treatment removed much but not all the advantage of late harvest to sprouting. None of the cultivars received sufficient cooling in the field to induce flowering under SD. Ten to twelve weeks storage at 15.5°C induced bulbs to flower under SD, but 4–6 weeks at 15.5°C was sufficient under LD. The temperature optimum (4.5–10°C) for early flowering was definitely lower than that for early sprouting (10°–15.5°C).
Bulb maturity is not only the attainment of a given age or size of bulb, but may reflect the extent to which a cold requirement for daughter elongation and flowering has been satisfied.
Roberts, A.N. and Moeller, F.W. (1971). VEGETATIVE AND FLOWERING RESPONSES OF LILIUM LONGIFLORUM THUNB. CULTIVARS TO COLD AND LONG DAY TREATMENT AS RELATED TO BULB MATURITY. Acta Hortic. 23, 58-65