Abstract
The effect of temperature and use of ethephon on growth in late-July flowering type chrysanthemums (‘Kosame’, ‘Michinoku’ and ‘Yayoi’) was investigated. Anthesis time fluctuated according to the temperature in each year. A delay in anthesis was caused by low temperatures during flower differentiation or high temperatures during flower development, and it was shown that the latter had more influence than the former. ‘Kosame’ showed the largest delay in anthesis due to both high and low temperatures, with inhibition of flower development after flower budding. ‘Michinoku’ represented a small fluctuation in anthesis time with flower differentiation and flower development before flower budding was inhibited only by low temperatures. The ‘Yayoi’ cultivar showed a medium delay of anthesis, with flower development after flower budding inhibited by high temperatures. Anthesis was also delayed by spraying ethephon, and the degree of the effect was different among the three cultivars. Ethephon mainly inhibited flower differentiation and flower development before flower budding. However, for ‘Kosame’ and ‘Yayoi’, there was a large fluctuation of anthesis due to ethephon spraying, with inhibited flower development after flower budding depending on temperature. During the development of early-August harvest by spraying ethephon, ‘Michinoku’ turned out to be suitable for early-August harvest because of the small fluctuations of anthesis. To harvest chrysanthemums in earlier August, it will be necessary research spray timing and frequency and to select suitable cultivars.
