Runkle, E. GrowingPlants with Green Light. Greenhouse Product News. 2017.
Greenlight — often neglected by lighting engineers — is a natural component of sunlight and an important part of any electrical light spectrum. But less extreme spectral tuning presents an opportunity for increased efficiency and control over plant traits. While it’s best to have all wavebands of the spectrum included in some proportion, increasing blue, red, or far-red light can elicit desirable characteristics in cannabis — like increased cannabinoids and terpenes.
 Bilodeau, S., et al. An Update on plant Photobiology and Implications for Cannabis Production. Frontiers inPlant Science. 2019.
The transmission of green into the lower canopy also decreases the senescence of the bottom leaves, and their sustained health lets them continue to help with photosynthesis. And green light drives photosynthesis directly too. In strong white light, green has been shown to drive photosynthesis more efficiently than red light. And the inclusion of 24% green light into a blue-red spectrum has been shown to enhance growth in lettuce. Without a doubt, the green light promotes growth.
Our Eyes and Green Light
In the lab, when a single leaf is exposed to blue light, its photosynthetic response is robust. Moreover, when chlorophyll a and b are extracted from the plant, they absorb blue and red light well. Greenlight, however, is poorly absorbed by extracted chlorophylls.
Another reason for green light’s exclusion from blue-red fixtures is a misinterpretation of laboratory studies. It’s well-documented that blue and red light are well-absorbed by plants and strongly drive photosynthesis. In fact, they’re the primary drivers of photosynthesis. The plant’s most abundant chlorophylls — chlorophyll a and chlorophyll b — absorbed and blue light.
 Terashima, I. et al. Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are green. Plant and Cell Physiology. 2009.
The Benefits of Green Light for Cannabis
So, when indoor growers are scouting their plants for pests, a fixture with the green light in the spectrum (i.e., a white-light spectrum) becomes an advantage. Under a blue-red light, recognizing pathogens like powdery mildew and fungus gnats can be next to impossible. When a spectrum includes even a small proportion of green, grow techs have a much easier time uncovering issues before they scale into major problems.
So, instead of green LEDs, lighting engineers use “white” LEDs that produce green light and other wavelengths simultaneously. It’s important to note that although some manufacturers reference green light, they’re typically referring to the white LEDs within the lamp.
In this article, you will learn about color spectrums that are needed for marijuana growth. Also, how grow lights colors affect marijuana growth.
Why is it important to take care of the spectrum?
The disadvantages of UV light for marijuana plants
UVB (280-315 nm)
The blue light spectrum is very important for marijuana plant growth. It is mainly responsible for increasing plant quality. During the vegetative stage of growing marijuana, you should aim for growing leaves as many as possible. The blue grow lights colors wavelength is from 450 to 490 nm. Indoor growers use T5 or T8 lighting fixtures, CFLs (compact fluorescent lamps), or metal halide bulbs that have a blue band of light. They use these for the first few weeks to achieve desired goals. When marijuana plants grow outdoors the angle of the sun during spring allows blue light energy which is abundant in this season to penetrate the leaves. Therefore, this blue light signals the plants to grow healthy and large leaves and to become strong. The plants that are deficient in blue light generally turn out yellow or pale and are weak and flopping. Blue light is essential for young plants and seedlings in vegetative stages to properly grow roots and stems.