I read this article from California Lightworks yeasterday curious about blue and red spectrum and finding the best way.
Using Spectrum Control with Cannabis
The exact way that plants use light is very specific to individual plant species and their natural environment. Evolution has produced a huge variety of plant strategies for growth and it is impossible to over generalize light responses. However, we do have a lot of practical experience with indoor cannabis growth results. Below are some general strategies and recommendations based on years of practical experiments with indoor lighting, including full spectrum LED systems.
The most common question we receive from growers in regards to spectrum control in cannabis cultivation is “What is the optimum Spectrum mix for Cannabis?” And the answer is it depends on what YOUR priorities are. Different spectrum mixes promote different plant morphology in different growth stages, and there simply isn’t one ideal. And that is the main benefit of LED’s over HID, the ability to use a varying grow light spectrum to design the plant for what you want from it.
There are basically 5 (or possibly more) different aspects to the end product in Cannabis that establish its value, and different people want different things.
1) Flower weight (ie. Overall flower yield)
2) Flower density (ie. Resin content and oil/wax ratio)
3) Flower cosmetic appeal (colors, structure, as well as density)
4) Fragrance (Strength i.e. terpene concentration and fragrance complexity)
5) Potency (THC and CBD levels)
What must be understood here is there is NO IDEAL SPECTRUM that will optimize ALL of these aspects of the final product simultaneously. Each can be individually optimized with LED plant lights but there will be tradeoffs. Goals of the Commercial grower:
What followers are SOME of the typical goals the average commercial grower might consider most important:
1) Some growers may want Maximum OIL yield for edibles etc. and the cosmetic aspects and fragrance of the flowers are not important. Potency is extremely important here.
2) Some may want maximum oil yield for top-shelf extracts, shatter etc…, where flower cosmetics are unimportant, but resin yield, resin quality (oil/wax ratio) and fragrance are very important. Potency is also important and often lab measured.
3) Some may want maximum Flower yield (weight) period. There numerous factors that play into this such as Resin content vs. flower matter (fiber), wax vs. oil, etc…, but these people only care about total flower yield by weight. With the market getting more and more competitive, this mindset will struggle to compete.
4) Because of the significant differential in price between top-shelf flower and lower quality or outdoor flower, (2x or more) most commercial growers are currently looking to maximize top-quality flower yield, ie. flower with high shelf-appeal, i.e. excellent cosmetics, fragrance, and density. Potency is important and often tested but typically considered strain specific and not considered that dependent on cultivation techniques.
So all these examples will have potentially DIFFERENT ideal spectrum mixes, and while those ideal spectrum mixes are not fully known, we can get you close. And please note, any fixed spectrum light source like HPS or MH will never have the ability to accomplish ideal results in any of these areas. That will require variable spectrum control.
Also please note: The single most important element in Cannabis yield is shaping the plant BEFORE peak flower production such that only flower sites see light. This cannot be stressed enough. The best indoor grow light and the best nutrients will not affect yield as much as insuring that only flowers sites and select sun leaves see light, and that all flowers left on the plant get enough light. Also critical to this process are the proper design, layout, and mounting heights of the UV LED grow light to minimize plant shading and create consistent lighting levels. Growth stages of Cannabis:
There are also generally 4 growth stages in cannabis that have different spectrum requirements.
Enhancing each aspect of plant growth can be a tradeoff. And. with the basics of our scientific understanding of Spectrum and Plant Morphology, we can now attempt to come up with some starting points for spectrum mixes for various end results. Please understand, these are starting points to using, for example, ultraviolet lights for plants, and you will need to experiment to reach the ideal for your environment, strain, and desired results.
Goal #1 above, Maximum OIL content for processed edibles, etc.
In this example, our goal is to maximize resin and really THC/CBD yield overall. This includes both flower AND leaves, stems, etc. So a good starting point in terms of Spectrum programs would be:
Veg: Obviously plant SIZE is the big driver at this point so a spectrum with full red and blue is important. In effect we are mimicking the sun, but with LED,s historically our best results in VEG are found with a RED/BLUE mix of around 60/40.
Pre-flower & Flower: In this case where only resin yield, not flower structure, is important, a higher blue component (ie. closer to sun) can be used rather than other approaches. A good starting point would be 70/30 RED/BLUE but possibly even more blue.
Ripening: Because we are already running extra blue in flower, no changes to light and frequency are probably necessary at this stage.
UVB: UVB supplementation is highly desirable in this approach because it can increase THC levels by as much as 30%. SO UVB should be supplemented for the last 5 weeks of flower minimum. Goal #2 – Resin for Extracts, shatter, etc.
In this example our goals are similar to Goal 1 above except there is a greater focus on Fragrance. SO, we can follow example 1 above except that in the ripen stage we will decrease the red a little more, to raise the Blue/Red ratio to stimulate terpene production more. Say 65/35.
UVB: UVB should be utilized all the way through the flower in this case because not only do we want to increase TCH in resin, but also terpene production and other pigments all the way through flower. Goal # 3 – Maximum Flower yield
Pure flower matter yield can be favored by running fairly high red levels all the way through, a good starting point would be 80/20. This is the kind of vegetative growth pattern seen with HPS. Goal#4 – Maximum Top-shelf flower yield.
This type of end product is the approach where having the ability to vary spectrum in all the different growth periods is most important, and where Hybrid Spectrum LED systems (individual Red/Blue/White control) significantly out perform all other types of lighting systems.
So a good starting point for this type of grow would be:
VEG: Depending on the inter-node spacing desired, decrease R/B ratio for shorter internodes, General recommendation: 60/40 for short tight internodes. This is the ratio found in the CLW VEG spectrum mix.
Pre-flower: To again reduce stretching, R/B ratio can be increased to 70/30 for the first 2 weeks of flower, or 75/25 for taller plants. Extra deep blue will stimulate additional pigments during this critical growth period enhancing flower colors and fragrance.
Flower: In this stage we want to maximize flower SIZE, so we will increase the Red/Blue ratio to 80/20. This is ratio that is found in the California LightWorks Full Cycle spectrum mix, or with the 550 series full on. Even higher Red ratios (by lowering the blue) can be used to further promote vegetative growth in plants, but there can be a sacrifice in resin, fragrance, and secondary pigments. There is always a tradeoff between flower mass and resin (density) /cosmetic quality. We do not advise an R/B ratio above 90/10, and for no more than a week or two in the middle of peak flower, or it will impact resin and fragrance. And too low, (for example 60/40) during this critical period will promote excess leaf content in the flowers and a fluffier structure akin to outdoor flower.
Ripen: Here we look to again enhance resin and terpenes (fragrance) so we suggest lowering the R/B ratio back down to 70/30 or even 60/40 for the last 2 weeks. At this point the higher blue ratio will not alter the flower structure or promote excess bud leaves, because flower growth is winding down, and transitioning to resin production.
Using Spectrum Control with Cannabis
The exact way that plants use light is very specific to individual plant species and their natural environment. Evolution has produced a huge variety of plant strategies for growth and it is impossible to over generalize light responses. However, we do have a lot of practical experience with indoor cannabis growth results. Below are some general strategies and recommendations based on years of practical experiments with indoor lighting, including full spectrum LED systems.
The most common question we receive from growers in regards to spectrum control in cannabis cultivation is “What is the optimum Spectrum mix for Cannabis?” And the answer is it depends on what YOUR priorities are. Different spectrum mixes promote different plant morphology in different growth stages, and there simply isn’t one ideal. And that is the main benefit of LED’s over HID, the ability to use a varying grow light spectrum to design the plant for what you want from it.
There are basically 5 (or possibly more) different aspects to the end product in Cannabis that establish its value, and different people want different things.
1) Flower weight (ie. Overall flower yield)
2) Flower density (ie. Resin content and oil/wax ratio)
3) Flower cosmetic appeal (colors, structure, as well as density)
4) Fragrance (Strength i.e. terpene concentration and fragrance complexity)
5) Potency (THC and CBD levels)
What must be understood here is there is NO IDEAL SPECTRUM that will optimize ALL of these aspects of the final product simultaneously. Each can be individually optimized with LED plant lights but there will be tradeoffs. Goals of the Commercial grower:
What followers are SOME of the typical goals the average commercial grower might consider most important:
1) Some growers may want Maximum OIL yield for edibles etc. and the cosmetic aspects and fragrance of the flowers are not important. Potency is extremely important here.
2) Some may want maximum oil yield for top-shelf extracts, shatter etc…, where flower cosmetics are unimportant, but resin yield, resin quality (oil/wax ratio) and fragrance are very important. Potency is also important and often lab measured.
3) Some may want maximum Flower yield (weight) period. There numerous factors that play into this such as Resin content vs. flower matter (fiber), wax vs. oil, etc…, but these people only care about total flower yield by weight. With the market getting more and more competitive, this mindset will struggle to compete.
4) Because of the significant differential in price between top-shelf flower and lower quality or outdoor flower, (2x or more) most commercial growers are currently looking to maximize top-quality flower yield, ie. flower with high shelf-appeal, i.e. excellent cosmetics, fragrance, and density. Potency is important and often tested but typically considered strain specific and not considered that dependent on cultivation techniques.
So all these examples will have potentially DIFFERENT ideal spectrum mixes, and while those ideal spectrum mixes are not fully known, we can get you close. And please note, any fixed spectrum light source like HPS or MH will never have the ability to accomplish ideal results in any of these areas. That will require variable spectrum control.
Also please note: The single most important element in Cannabis yield is shaping the plant BEFORE peak flower production such that only flower sites see light. This cannot be stressed enough. The best indoor grow light and the best nutrients will not affect yield as much as insuring that only flowers sites and select sun leaves see light, and that all flowers left on the plant get enough light. Also critical to this process are the proper design, layout, and mounting heights of the UV LED grow light to minimize plant shading and create consistent lighting levels. Growth stages of Cannabis:
There are also generally 4 growth stages in cannabis that have different spectrum requirements.
- Vegetation – In Vegetation (VEG) stage, rapid, healthy overall plant and root growth is desired, and in general most growers desire maximum growth but with shorter compact plants with short inter-nodal spacing preferred.
- Pre-flower – Pre-flower is the period from when the 12/12 flower cycle is first initiated, to roughly the end of the second week (in an 8-week flower), or until the small flowers are prevalent and the rapid growth stretch slows. Again, for most growers, the desire in this stage is to maximize SIZE, while limiting stretch.
- Flower – The peak Flower period is generally from week 3-7 and is the time when the plant (stem / leaf) growth stops and all the plant energy focuses on flower production. Maximum flower matter size and good structure is generally the goal here.
- Ripen or Finish – The Ripen period is generally from week 7 to finish (in an 8-week flower) where the Flower growth, (i.e. size) slows and plant energy refocuses on resin and terpene production. This is the period where the flower acquires a significant portion of its density, ie. resin content. This transition is not clearly defined, and some strains have big increases in resin production during this period, and others not as much.
Enhancing each aspect of plant growth can be a tradeoff. And. with the basics of our scientific understanding of Spectrum and Plant Morphology, we can now attempt to come up with some starting points for spectrum mixes for various end results. Please understand, these are starting points to using, for example, ultraviolet lights for plants, and you will need to experiment to reach the ideal for your environment, strain, and desired results.
Goal #1 above, Maximum OIL content for processed edibles, etc.
In this example, our goal is to maximize resin and really THC/CBD yield overall. This includes both flower AND leaves, stems, etc. So a good starting point in terms of Spectrum programs would be:
Veg: Obviously plant SIZE is the big driver at this point so a spectrum with full red and blue is important. In effect we are mimicking the sun, but with LED,s historically our best results in VEG are found with a RED/BLUE mix of around 60/40.
Pre-flower & Flower: In this case where only resin yield, not flower structure, is important, a higher blue component (ie. closer to sun) can be used rather than other approaches. A good starting point would be 70/30 RED/BLUE but possibly even more blue.
Ripening: Because we are already running extra blue in flower, no changes to light and frequency are probably necessary at this stage.
UVB: UVB supplementation is highly desirable in this approach because it can increase THC levels by as much as 30%. SO UVB should be supplemented for the last 5 weeks of flower minimum. Goal #2 – Resin for Extracts, shatter, etc.
In this example our goals are similar to Goal 1 above except there is a greater focus on Fragrance. SO, we can follow example 1 above except that in the ripen stage we will decrease the red a little more, to raise the Blue/Red ratio to stimulate terpene production more. Say 65/35.
UVB: UVB should be utilized all the way through the flower in this case because not only do we want to increase TCH in resin, but also terpene production and other pigments all the way through flower. Goal # 3 – Maximum Flower yield
Pure flower matter yield can be favored by running fairly high red levels all the way through, a good starting point would be 80/20. This is the kind of vegetative growth pattern seen with HPS. Goal#4 – Maximum Top-shelf flower yield.
This type of end product is the approach where having the ability to vary spectrum in all the different growth periods is most important, and where Hybrid Spectrum LED systems (individual Red/Blue/White control) significantly out perform all other types of lighting systems.
So a good starting point for this type of grow would be:
VEG: Depending on the inter-node spacing desired, decrease R/B ratio for shorter internodes, General recommendation: 60/40 for short tight internodes. This is the ratio found in the CLW VEG spectrum mix.
Pre-flower: To again reduce stretching, R/B ratio can be increased to 70/30 for the first 2 weeks of flower, or 75/25 for taller plants. Extra deep blue will stimulate additional pigments during this critical growth period enhancing flower colors and fragrance.
Flower: In this stage we want to maximize flower SIZE, so we will increase the Red/Blue ratio to 80/20. This is ratio that is found in the California LightWorks Full Cycle spectrum mix, or with the 550 series full on. Even higher Red ratios (by lowering the blue) can be used to further promote vegetative growth in plants, but there can be a sacrifice in resin, fragrance, and secondary pigments. There is always a tradeoff between flower mass and resin (density) /cosmetic quality. We do not advise an R/B ratio above 90/10, and for no more than a week or two in the middle of peak flower, or it will impact resin and fragrance. And too low, (for example 60/40) during this critical period will promote excess leaf content in the flowers and a fluffier structure akin to outdoor flower.
Ripen: Here we look to again enhance resin and terpenes (fragrance) so we suggest lowering the R/B ratio back down to 70/30 or even 60/40 for the last 2 weeks. At this point the higher blue ratio will not alter the flower structure or promote excess bud leaves, because flower growth is winding down, and transitioning to resin production.
