Exploring light for growth control in ornamental plant production using LEDs in controlled environments
Plant growth regulators are common in production of certain ornamentals to increase plant compactness. This research evaluated effects of light quality on plant morphology for non-chemical growth control. Reductions in red-to-far red ratio (R:FR) representing hanging basket shading were simulated in growth chambers, which increased bedding plant height. Bedding plant morphology differed drastically between LED and fluorescent treatments, proving spectrum is important for morphological control. Five end-of-day (EOD) treatments containing red (R) and blue (B) light combinations were tested for bedding plant growth control. Treatments of 100B, 75B:25R, and 10B:90R reduced petunia height by 12%–14%, but no treatments differed from control in other species. Finally, EOD R light and blackout (BO) were evaluated on Easter lily growth and flowering. BO reduced lily height by 11% compared to control without reductions in dry weight or flower number, but EOD R produced no effects. Further testing of EOD treatments is warranted.