How to Force Long-Day Perennials into Flower with High-Intensity LEDs

Growers who force perennials into flower know they will fly off the bench at retail, as most perennials are sold without flowers. Consequently, growers are looking for easy and profitable forcing protocols to produce a wide variety of high-quality flowering perennials in the spring. Until recently, growers used incandescent lamps (INC) to provide low-intensity (~1 to 3 µmol∙m−2∙s−1) photoperiodic lighting to extend the day or interrupt the night. These lamps provided a low-red to far-red light ratio (R:FR) that induced long-day plants into flower. Unfortunately, a low R:FR can also result in unwanted stem elongation and stretching.