Responses of Garden Chrysanthemums to Daylength

in HortScience
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  • 1 Department of Environmental Horticulture, University of California, Davis, CA 95616

Garden chrysanthemums [Dendranthemum ×grandiflorum (Ramat.) Kitamura] are characterized by early flowering in September and October when grown out-of-doors and by rapid flowering in short days (SD). However, as rooted cuttings of these cultivars frequently have flower buds present at the time of planting, their true response to daylength cannot readily be determined. Vegetative shoots were obtained by growing rooted cuttings in long days (LD), removing the terminal bud, and then pinching the emerging side shoots at a very early stage. On transfer to SD, the vegetative secondary side shoots quickly initiated flower buds that developed to anthesis more rapidly than those of `Bright Golden Anne' (BGA), a lo-week response group cultivar. `Bandit', `Buckeye', `Compatriot', `Freedom', `Jackpot', and `Sunburst Cushion' appeared to be in the 7-week response group, with `Baby Tears' in the 6-week and `Powder River' in the 8-week response groups. All cultivars rapidly initiated flower buds in LD and, although they produced significantly more leaves than in SD, flower initiation began within ≈13 LD from pinching. When pinched twice and grown using black cloth in summer, garden chrysanthemums can form attractive, uniformly flowering pot plants. Their rapid-flowering characteristic could also be of value in breeding programs for cut-flower chrysanthemums.

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