Abstract
The effects of changed night temperature setting (10 to 15°C) in winter on the flowering, yield, and form of spray-type carnations (Dianthus caryophyllus L.) were investigated. Spray-type carnation cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ were planted in four greenhouses on June 27, 2008, pinched on July 18, and pinched again on September 5. The night temperature in the greenhouses was kept at 10°C from November 20. It was changed to 15°C from December 1, January 9, or February 18, in three night temperature-changed treatments, or maintained at 10°C throughout the experimental period (control). All treatments were continued until April 30. Three primary lateral shoots were not influenced by the night temperature in winter because they were harvested until December. In both cultivars, the number of days from pinching to flowering decreased in secondary lateral shoots that sprouted from decapitated primary shoots. The yield of cut flowers between January and March increased as the night temperature increased from December 1. Therefore, the total yield of cut flowers paralleled that from January to March. The length and weight of cut flowers showed a tendency to decrease at a 15°C night temperature. In ‘Light Pink Barbara’, the number of florets also showed a decreasing tendency at 15°C. In ‘Cherry Tessino’, the diameter of florets showed a decreasing tendency as the night temperature increased from December 1. As the results, high quality cut flowers were produced in all treatments when the night temperature was elevated to 15°C. In conclusion, it was shown that the change of the winter night temperature to 15°C from December 1 increased the yield of cut flowers in winter of spray-type carnations cultivars ‘Light Pink Barbara’ and ‘Cherry Tessino’ while maintaining a high cut flower quality.
