The Spectrum of Productivity: Exploring the Impact of Red–Blue and Red–Blue–Green LED Light on the Growth and Reproductive Stages in 'Festival' Strawberry

Optimising light spectra is critical for enhancing plant growth, physiological efficiency, and reproductive success in controlled environment agriculture. This study investigates the effects of red–blue (RB) and red–blue–green (RBG) LED light treatments on the growth, physiological responses, flowering, and fruiting of Fragaria × ananassa cv. Festival (Festival strawberry). Plants grown under RB light exhibited significantly enhanced vegetative growth compared to those under RBG. Specifically, RB light treatment resulted in taller plants (25.30 cm) with more petioles (12.28), outperforming RBG (22.80 cm and 7.99, respectively). Physiological efficiency, indicated by chlorophyll fluorescence (Fv/Fm), was also superior under RB (0.78) than under RBG (0.76). These findings demonstrate the pronounced effect of RB light in enhancing vegetative parameters. Reproductive development was profoundly influenced by light spectra. RB light significantly accelerated flowering, with plants flowering in 53.57 days, compared to the delayed response under RBG (102.25 days). Fruit yield was substantially higher under RB, with an average of 7.3 fruits per plant, compared to only 2.0 fruits per plant under RBG. Interestingly, fruit quality attributes, including fruit length, weight, and soluble solids concentration (Brix), were not significantly influenced by the inclusion of green light in the RBG spectrum. These results suggest that green light does not provide a measurable advantage for improving fruit quality, further highlighting the effectiveness of RB light in driving key growth and reproductive traits. Heatmap analysis visually confirmed RB light’s superior ability to promote growth, early flowering, and reproductive output, while RBG light treatment exhibited limited benefits, often diminishing the effects of red and blue light. These findings underline the critical importance of red–blue light combinations in optimising plant productivity, particularly during the reproductive stage, in controlled environment systems such as vertical farms and plant factories. Future studies should explore fine-tuning spectral ratios and light intensities to further maximise productivity, resource efficiency, and crop quality, paving the way for sustainable horticultural practices and enhanced food security.