Effects of Short-term End-of-day or End-of-night Heating on the Flowering of Winter-cultivated Spray-type Carnation (Dianthus caryophyllus L.) Cultivars

The effects of short-term heating applied as a 4-h end-of-day (EOD) or end-of-night (EON) heating on the flowering of winter-cultivated spray-type carnation (Dianthus caryophyllus L.) cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ were investigated. Furthermore, the effects of a night temperature of 5 or 10°C after EOD heating were also investigated. In both cultivars, days to anthesis decreased with short-term heating treatments. Yields of cut flowers from January to March in EOD and EON heating treatments were almost equal, and higher than in the control. However, EON heating adversely affected the flower quality, resulting in a lower weight of cut flowers and decreased number of florets. When EOD heating was followed by a lower night temperature (5°C), the yield of cut flowers was equal compared with the control treatment, but the energy needed for greenhouse heating in winter was reduced. In conclusion, it was found that EOD heating was more preferable as short-term heating to promote the flowering of winter-cultivated spray-type carnation cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ while maintaining cut flower quality, and the lower night temperature after EOD heating was effective to reduce energy use in winter while maintaining the yield of cut flowers.