Flowering Responses of Alstroemeria Cultivars to Air and Soil Temperatures

Flowering responses of 'Regina', 'Carmen' (syn. 'Cana') and 'Wilhelmina' Alstroemeria to air and soil temperatures were studied for producing cut flowers in a soil cooling system. 1. Chilling requirements for flowering shoot production were 3∼6 weeks at 2°C for 'Wilhelmina', 6 weeks for 'Carmen' and more than 10 weeks for 'Regina'. 2. 'Regina' plants stopped producing flowering shoots when rhizomes were kept at 25 and 18°C but continued to produce flowers at 14°C, irrespective of air temperatures. 3. Rhizomes of 'Regina' plants, subjected to 15°C or lower for at least 6 hr per day, continued to produce flowering shoots although the number of vegetative shoots increased as compared to rhizomes exposed to a continuous chilling treatment. 4. Chilled 'Regina' and 'Carmen' plants ceased flowering subsequently when they were exposed to 28/22°C (12 hr day/12 hr night) for 4 and 10 weeks, respectively.