Supplemental Low-Irradiance Mono/Polychromatic LED Lighting Significantly Enhances Floral Biology of the Long-Day F1 Hybrid Strawberry ‘Soraya’ (Fragaria x ananassa Duch.)

Floral and vegetative responses of the strawberry (Fragaria x ananassa Duch.) to specific light wavelengths are not well documented. LED lights make it feasible for precise exposure to specific wavelengths during a 24 h cycle to alter growth responses regulated by phytochromes and cryptochromes and thereby potentially enhance fruit productivity in both a controlled environment and field systems or to enhance stolon production for controlled environment propagation. This research developed a systematic method to assess the effects of supplemental, low-irradiance LED lighting on strawberry flowering and vegetative biology. Growth of the long-day F1 seed-propagated cultivar ‘Soraya’ was evaluated during and following 6 or 12 weeks of exposure to supplemental red (660 nm), far-red (730 nm), blue (454 nm), or incandescent lighting at various times during the dark period of a 24 h cycle under a 10 h non-inductive photoperiod at non-inductive temperatures (>27/18 °C, day/night). Treatment effects were monitored via flower mapping and phenology during treatment, field and greenhouse production after treatment, and floral scores derived by ranking treatment effects within the evaluation method and then combining them into a single, simple score. The most promising treatment for enhancing the floral nature of plug plants was exposure to far-red + red light as a 5 h night interruption. This treatment increased inflorescence production in the greenhouse by 285% and resulted in multi-branched, floral plants with the potential for enhancing yield in either greenhouse or field production. Greenhouse runner production increased by 483% following exposure to incandescent lighting at the beginning of the dark period; thus, this treatment or one using a spectral distribution similar to incandescent may be suitable for enhancing vegetative propagation in controlled environments.