What wavelength or color of light is best for starting seedlings?

• A. red
• B. blue
• C. green
• D. yellow

Answer: (B)

Seedling growth responds to light color, and blue light is the most influential for starting strong, compact plants. Blue light, with shorter wavelengths, promotes healthy leaf development and helps build a sturdy, non-etiolated stem by guiding photomorphogenic responses. It also supports chlorophyll production and efficient vegetative growth. Red light can encourage elongation if blue is scarce, leading to leggier seedlings, while green light is largely reflected and doesn’t drive growth as effectively. Yellow isn’t a primary driver for seedling vigor. So, when you’re choosing a single color for starting seeds, blue provides the best foundation for healthy, stocky seedlings.