Despite increasing demand for new and locally grown specialty cut flowers, protocols for year-round production are limited. An advantage of greenhouse production is the ability to control environmental parameters such as temperature, light intensity, and photoperiod. The implications for commercial production include implementing strategies to hasten or delay flowering to meet market dates. Therefore, our objective was to determine if photoperiod and low temperature influences flower induction and development, time to harvest, yield, and morphology of bluebeard (Caryopteris incana), Billy buttons (Pycnosorus globosus), ranunculus (Ranunculus asiaticus), and dahlia (Dahlia hybrida). Based on our results, we classified bluebeard as a facultative short-day (SD) plant for flower induction and an obligate SD plant for flower development, and Billy buttons as a day-neutral plant for flower induction and a facultative long-day plant for flower development. Growers should provide bluebeard with a 16-h photoperiod or night interruption lighting for 4 to 6 weeks to promote vegetative growth, followed by an 11- to 14-h photoperiod for flower induction and development. A photoperiod 12 h hastens time to harvest and increases yield and stem quality of Billy buttons. In ranunculus, subsequent flowering was faster following a low-temperature treatment. To ensure marketable stem length, ranunculus should be finished under a 12-h photoperiod. Time to flower and stem length of dahlia was influenced by the duration of photoinductive short-day cycles. As few as 5 and 10 photoinductive SD cycles provided to dahlias can ensure a timely harvest and marketable stem lengths. Our results indicate that photoperiod influences flower induction of all specialty cut flower species investigated, and that controlling photoperiod can hasten flowering and improve flower quality and yield.
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