Sunlight contains a range of colors---all the colors of the rainbow and more that can't be seen. Different colors of light affect plant growth in different ways. Some light---ultraviolet light, or UV---is even harmful to plants, just as it is to humans.
A rainbow shows different colors of light; blue and red are most helpful to plants.
UVC light (short-wave, germicidal UV) is toxic and dangerous to plants, while UVB light (medium-wave UV) causes the colors of plants to wash out. UVA light (long-wave UV or black light) has a neutral effect on plant growth.
The blue part of the spectrum encourages plant growth, especially leafy growth, preventing plants from becoming too leggy.
Red and orange-red light cause plants to increase budding and flowering, which leads to fruit. A downside of the light is that, without blue light, plants can become leggy.
The infrared range of light on the spectrum is not helpful to plants because all the energy changes to heat instead of being converted to chemical energy that would eventually feeds the plant.
Light with all colors is called full-spectrum light. Full-spectrum fluorescent bulbs labeled 2700 to 3000 kelvins provide more red, while bulbs labeled 5000 to 6500 kelvins provide more blue.
Green, Yellow and Orange Light
Though photosynthesis occurs in plants as a result of green, yellow and orange light, the rate of photosynthesis is less than that triggered by red and blue light.
- MadSci Network: Botany-Washington University Medical School
- How Sunlight Afffects Plant Growth
- Ask the Builder
- Light Requirements of Houseplants
light color and plants, colored light and plants, plant growth and light
About this Author
Sophie Johnson is a freelance writer and editor of both print and film media. A freelancer for more than 20 years, Johnson has had the opportunity to cover topics ranging from construction to music to celebrity interviews.