Plants use all colors of light for photosynthesis, including green and yellow, but blue and red light are the most important colors on the visible light spectrum for promoting plant growth. Blue light is essential during a plants germination phase, while red light impacts plant growth in several ways, including during the blooming and flowering phase. Red light primarily supports the growth of stems and expansion of leaves and regulates flowering, germination, and dormancy, while blue light is responsible for chlorophyll production, root growth, and leaf thickness. Green light helps to regulate the “night” cycle while you navigate the grow room to maintain your plants, and yellow light is not needed much for plants to grow strong and healthy.

Ideally, the best horticulture lights will contain a red to blue ratio of 5:1. However, the entire PAR spectrum (including green and yellow light) is important to supporting balanced, healthy plant growth. While more of some colors promote higher growth in specific stages, no single color of light is better for encouraging plant growth. Instead, the optimal color spectrum of light for plant growth depends on the plants lighting needs and growth stage.