Effects of Light-Emitting Diode Grow Lights on the Growth and Yield of Hong-Tai Bok Choy and Baby Bok Choy

Light-emitting diodes (LEDs) are increasingly being applied in controlled-environment agriculture due to their energy efficiency and spectral flexibility; however, crop-specific responses to different LED spectra remain unclear. This study evaluated the effects of four commercial LED lamps compared with sunlight on the growth, soil plant analysis development (SPAD), leaf color, and biomass production of Hong-Tai Bok Choy (Brassica rapa subsp. chinensis) and Baby Bok Choy (B. rapa subsp. chinensis). A completely randomized design with four light treatments was employed, and growth traits—SPAD values, leaf color indices, fresh weight, and dry weight—were measured at 35 days after sowing. Data were analyzed using an Analysis of Variance (ANOVA) followed by Duncan’s multiple range test (p ≤ 0.05). LED treatments significantly enhanced biomass accumulation relative to sunlight. Hong-Tai Bok Choy achieved the highest fresh (167.53 g plant−1) and dry weights (10.32 g plant−1) under the pink LED, whereas Baby Bok Choy showed maximum fresh (110.79 g plant−1) and dry weights (6.61 g plant−1) under the 4000 K white LED. In contrast, sunlight (reference treatment) resulted in higher SPAD values and superior leaf color. These results demonstrate that commercial LEDs improve yield performance, with optimal LED lamps differing between crop types, highlighting the importance of species-specific LED selection in controlled-environment vegetable production.