2012 Volume 11 Issue 4 Pages 537-543
Oriental hybrid lilies show low cut flower quality, such as a shortened stem length and cleaved flowers, in high-temperature seasons. To achieve stable cut lily flower production in summer, the night temperature of a greenhouse was controlled using a heat-pump system. Bulbs of ‘Siberia’ lily were planted in two greenhouses with and without night temperature control in August. When the greenhouses were cooled during the night, the air temperature during the day and soil temperature also dropped. Plants grown in a greenhouse controlled at 19–22°C during the night showed flowers with a longer stem and lower frequency of cleaved flowers compared with those in a greenhouse with an ambient temperature. When night cooling was performed only 3–4 weeks after planting in early August, the plants produced longer stems similarly to those grown under cool night temperature conditions until flowering. No difference in the bulb dry weight was observed regardless of the night temperature. Increased dry weights were observed in the stem, leaf, flower buds, and especially stem roots of plants grown under cool night temperature conditions compared with plants grown under ambient temperature conditions. The vigorous growth of lilies under cool night temperature conditions is due to the development of stem roots that provide adequate water and nutrient absorption.
