Natural light shows white, but it is actually made up of different colors. Our plants can grow well under these different colurs. When we use grow light to instead sunshine, should we copy the sun light and make it the same as sun light? Green light sometimes used as a tool for eliciting specific plant responses like photomorphogenic growth. If it is must for plants? The most readily available light from the sun is green, yellow and orange. These are the primary frequencies that human eyes use. However, studies show that these are the least used light frequencies in plants. Most of the photosynthetic activity is in the blue and red frequencies, which makes full spectrum LED grow lights so beneficial. How cannabis germinates, grows and even makes buds are affected by different color spectrum. We have no much choice to change the spectrum of sunlight when growing outdoors, but when we use grow lights to grow indoor, we can control and choose the spectrum that plants need. Next let’ see what spectrum needed for veg an flowering. Veg: based on growers’ feedback and spectrum studies on some leds suppliers’ website, blue is the most important, then it is red, few of them mentioned green. Pre-flower & Flower: red is the most important, then it is blue, also few growers mentioned green.
In order to prove if green is a must for plants, we have got data sheets from different spectrum study universities and grow lights manufactures website to see how red, blue and green will affect the yield and stem length. ( pictures below)
From the first two pictures, we can see 86% red+12% blue+2% green can help you get highest yields. When we use 92% green+7% blue+1% green, yield is lowest. When more green is used from 40%-48%, yield decreases. Then let’s look at the last picture: when we use 86% red+12% blue+2% green, stem length is shortest, this is what most of growers want. When 98% red+2% green used, stem length is longest. In conclusion: green is useful for Cannabis growth and yields, but it only plays a very very small role.
Cant get to red untill blue hads been around a while for vegg first..!! Flower tent Vegging outside the flower tent
Most white horticulture LEDs today already have some green in their spectrum. For instance, here is the spectrum for qb288 quantum boards: As you can see, even at 2700k these boards have a decent amount of green, probably more then needed anyway.
Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green excite Grow Lights Europe https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0163121
Green light penetrates deeper into leaves and deeper into canopies. Sun et al. [29] found that RL and BL drive CO2 fixation primarily in the upper palisade mesophyll while GL drives CO2fixation in the lower palisade. Once the upper part of individual leaves and the upper canopy are saturated by RL and BL, additional GL should be beneficial in increasing whole plant photosynthesis [30]. Indeed, Terashima et al. [31] found that GL increased single leaf photosynthesis more than RL or BL at high PPF. In contrast to measurements of photosynthesis in single leaves at low light, a higher fraction of GL has the potential to increase whole-plant photosynthesis both in the bottom of upper leaves and by transmission to lower leaves.
Short answer is we are just beginning to understand how important the green part of the spectrum is but recent research indicates that especially in veg it can be as important as red for overall plant development and light manufacturers were foolish for leaving it out.
Out of all the lights I've used the HLG qb96 elite v2 has the best plant response. Look at the amount of green, blue, and the long red curve with the deep red spike. Wider is better. Compared to a straight qb288 white light 3k board. No wonder it grows better. More blue, more green, peak power shifted further red and a larger red curve.
If you look a that curve on the qb96 the blue has a higher peak then the green and the red is the largest percentage of the light. The one thing I didn't like much about the spectrum tests that Sara posted is they were limited on what options they tried. Try one with 25% green 35% blue and 40% red with some included far red. That's closer to what I'm growing with.
My research before buying lighting actually indicated a bit of the green is actually beneficial to plants. And you’re right, we want to best mimic the Sun with our LED lights for better success!
I agree with every thing in this thread. Green light does plays a role. Lights like the qb96's are going done the right path. BL