2017 ASHS Annual Conference

Foliage plants are grown for their brightly colored or patterned leaves and are increasingly being incorporated into mixed annual combination planters, therefore, vegetative growth is desired over flowering. Additionally, the flowers are not visually appealing and can stall vegetative growth, also reducing cutting yield. Therefore, our objective was to determine the photoperiodic flowering responses of several foliage annual plants. Photoperiods consisted of a 9-hour day that was extended to 10, 12, 13, 14, or 16 hours with lamps containing red (R), white (W), and far-red (FR) light-emitting diodes (LED) (R:FR = 0.67); an additional treatment was a 9-hour day with a 4-hour night interruption (NI) from lamps containing R:W:FR or R and W LEDs (R:FR = 53.35). Nearly all bloodleaf plants (Iresine herbstii), josephs coat (Alternanthera) ‘Red Threads’ and ‘Brazilian Red Hots’ grown under 9, 10, and 12-h photoperiods flowered less than 10 weeks after transplant. Bloodleaf and josephs coat ‘Red Threads’ plants grown under 13-h photoperiod had visible buds while those grown under 14, 16, or 9-h with NI photoperiods did not flower or have any visible buds 10 weeks after transplant. Josephs coat ‘Brazilian Red Hots’ did not flower or have a visible bud under 13, 14, 16-h, or NI photoperiod treatments. Stem elongation of all foliage plants was greatest in treatments containing FR light. Based on our results, josephs coat ‘Red Threads’, josephs coat ‘Brazilian Red Hots’, and bloodleaf plant can be classified as short day plants requiring a day length of 14-h or greater or NI to inhibit flowering. Red and W light is as effective as R, W, and FR light at inhibiting flowering, therefore, FR light is not necessary.