Application of Photoperiodic Manipulation in Vegetative Specialty Floral Crop Propagation and Flowering

Abstract

Photoperiod requirements are important for optimum flower development, decreasing production time, year-round flowering, and/or for increasing vegetative growth necessary in stock plant production. The photoperiodic responses were determined for 24 vegetatively propagated specialty floral crops. Each plant species was grown at 8-, 10-, 12-, 14-, and 16-h photoperiods. Photoperiods were provided by 8 h of sunlight, then pulling black cloth and providing daylength extension with incandescent bulbs. Data collected included time to flower, flower number, and vegetative characteristics. Evolvulus nuttallianus `Blue Daze', Heliotropium arborescens `Fragrant Delight', and Orthosiphon stamineus `Lavender' were facultative short-day plants with respect to flowering. Time to flower increased as photoperiod increased. Duranta repens `Blue', Verbena hybrid `Tapien Lavender', and Verbena peruviana `Trailing Katie' were facultative long day plants with respect to flowering. Days to visible bud and first open flower decreased as photoperiod increased. Argeranthemum frutescens `Sugar Baby', Scaevola aemula `Fancy Fan Falls', and Portulaca hybrid `Apricot' had increased flower number as photoperiod increased from 8- to 16-h, although time to first flower initiation was not affected. Abutilon hybrid `Apricot', Duranta repens `Blue', Evolvulus nuttallianus `Blue Daze', Lotus berthelotii `Parrot's Beak', Lysimachia nummularia `Aurea Creeping Golden', Rhodanthe anthemoides `Milkyway', and Scaevola aemula `Fancy Fan Falls' had increased vegetative growth as photoperiod increased. All other species studied were day-neutral with regard to flowering and vegetative parameters.