TOPICS > GROWING MARIJUANA > GROWING MARIJUANA: ADVANCED TIPS > THE BEST LIGHT SPECTRUM FOR CANNABIS
THE BEST LIGHT SPECTRUM FOR CANNABIS
vIDEO TRANSCRIPT
Hi, I’m your prof from Indica Institute, and this is my advanced cannabis growing course entitled “Growing Cannabis 201: Advanced Grow Tips.” I’ve designed this course to help and instruct people on how to grow cannabis plants to obtain better results in terms of overall plant health, yield, taste and more. The course covers a variety of topics including best practices for germination techniques, cloning, transplanting, grow medium, grow environment and nutrients. Visit me at Indica Institute or my YouTube channel for a list of cannabis related courses, tips and more. I hope you find the video useful, and please like and subscribe so I can continue making more videos like these!
Hi and welcome to my guide on cannabis plant grow light spectrum, and how to properly use it for the best results at harvest. The objectives of this lesson are to learn what spectrum of light cannabis plants need to thrive, what the growth goals of cannabis plants are at each stage of development, how each light spectrum range affects cannabis plant growth, and how the goals for each stage of cannabis growth can be optimized using the correct light spectrum ratio and intensity levels to manage plant growth patterns.
All links mentioned in this video can be found in the video description, along with a link to Indica Institute where you can find a growing list of cannabis related courses and recommendations on the best products for purchase. I’d also like to give a special thanks to my partners at FourBudz grow equipment for supporting free cannabis education. You can check them out at fourbudz.com.
When creating the optimal environment for growing your cannabis plants indoors, there is no factor that has more of an impact on your yields and the quality of your buds than your lighting. Therefore, knowing the full range of light spectrum and how each nanometer range of light affects your plant is a tool in your greenhouse toolbox that will have immediately noticeable results on your plants.
First off, cannabis plants thrive off of a full spectrum light band, from UVB to Infrared. The ratios and intensity of each light range vary in their benefits for the plant at each stage of growth though, so it’s beneficial to know the effects each range of light has on cannabis plants.
For instance, UVA and UVB have an interesting effect on cannabis plants. Similar to the effects of UV on human skin, UV light rays damage plants, stressing them into producing trichomes in an effort to protect themselves from the rays. This is especially true of UVB and cannabis during the last few weeks of flowering, this is known as the resin substage of flowering. When exposed to low levels of UV light during this stage, cannabis plants have been shown to increase trichome production density by as much as 30%.
So what is the significance of more trichomes? Well, these little mushroom shaped growths found on your buds and sugar leaves contain cannabinoids, and therefore the more of them there are in a given area, the more potent your buds will be. As such, using UVA and UVB spectrum light to increase trichome count on your plants will increase overall cannabinoid density, and therefore the potency of your buds.
Unfortunately, you will find with HID bulbs that UV spectrum light is generally filtered out due to the thick glass walls of the bulb. Fluorescent light spectrum is not optimal for plant growth in the first place, and is noticeable simply based on yields alone. As well, most LED lights do not have UV light, and if they do only the best ones have UVB. Generally assume that the $100 cheap boxes you find on Amazon or any non safety certified LEDs won’t be carrying this vital spectrum range of light.
Moving more into the mid range blue light, this spectrum range promotes shorter internodes and therefore stalkier plants. Stalkier plants are more desirable when growing indoors because the further the bulk of your plant is from your light, the smaller your buds will be as a result. This is because the light becomes less intense the further it has to travel to the bud site, so short condensed plants allow for greater grow light optimization. On the other hand, tall stretched out plants may have decent sized colas, but they lack size and bud density further down the plant as you move away from the light.
Additionally, blue range light regulates seedling growth and promotes vegetative growth, although too much blue light without accompanying full spectrum ranges could result in health problems for your plant, such as leaf edema. Similar to UV spectrum light, though to a lesser extent, blue range light is known to help with terpene and trichome production in the flowering stage, stimulating the secondary pigments of the plant that enhance flavour, colour and fragrance. Contradictory to the effects of red spectrum light, too much blue spectrum light during the flowering and late flowering stages will result in less overall bud density and yields, but greater concentrations of essential oils and theoretically more cannabinoids due to increased trichome production levels.
There is less data on the exact effects of green spectrum range light on cannabis plant growth, as many studies are still generally inconclusive. For instance it was initially thought that green range light wasn’t readily absorbed by chlorophyll plants because it’s poorly absorbed in a chlorophyll solution. Although with further research it turns out that other pigments in the plant do absorb green light and continue on to contribute to plant growth and photosynthesis. The effects of this light is interesting though, as it seems to depend on its intensity and mixture ratios with other spectrum ranges. A little amount of green light and the results tend to mimic the effects of blue range light on plants, creating shorter stems and leaves. A large amount of green light seems to have the opposite effect though, more in line with the effects of far red spectrum light which stretches the plant. The takeaway from this is essentially that green light is beneficial, though in small doses, and in congruence with a full spectrum range of light.
Meanwhile yellow light helps to promote germination and long stems, and a small amount during flowering has been proven to increase production of bud sites and density.
Red range light promotes height growth in plants, especially in the early stages of flowering. The intensity and ratio mixture of light being provided to the plant plays a factor in whether this growth is good or bad - as too much red light in relation to accompanying spectrum bands can cause unwanted stretching. Aside from this, it’s known to promote stem growth, flowering and bud matter production in cannabis plants.
Far range red and infrared light promotes bud production as strongly as red, though if the intensity or ratio mixture in relation to accompanying spectrum band has too much infrared light it can cause unwanted stretching in the plant. This is mainly because while red light is easily absorbed by the plant canopy, far red and infrared light penetrates canopy surfaces. Therefore if there’s a high level of this light being absorbed by your plants, they will think they’re under a competing plant canopy and stretch in an attempt to rise above the competitor plants for survival.
So now that you know how light affects your cannabis plants, it's important that you utilize this information to get the most out of your plants at each stage of growth. While your plants will benefit from a full spectrum range of light throughout its life cycle, knowing what the growth goals of your plants are at each stage, and providing the optimal spectrum to achieve these goals will result in yields and buds that are nothing less than top notch.
For instance during the vegetative stage of growth you should be focused on promoting quick and healthy root growth in your cannabis plants. The best approach would be to foster overall growth in the plants while keeping tight internodal spacing. The advantage to this is your plants will have the structure in place to grow the same yields as taller plants, but because they are more stout your grow lights will be able to reach more bud sites with greater ease and stronger intensity levels. This will lead to larger bud density and higher overall yields.
For those using HID lighting, the use of Metal Halide light bulbs during this stage is optimal. If growing using fluorescent lighting, T5 lighting is great for vegetative growth but can lead to some stretching if not used correctly. For those using LED lighting, many of the cheaper lights on the market do not offer spectrum control and therefore you are out of luck when it comes to growth stage optimization. For those growers that have lights with a veg and bloom switch, the veg option should be used as long as it is not all just blue light. As stated before, too much blue light can lead to health issues with your plant. Optimally, you’d be using an ETL safety certified LED light with custom spectrum control options, like my FourBudz light. This way you can keep a full spectrum of light, but drop red range light intensity in favour of blue to obtain the desired growth results for this stage. During the vegetative stage I turn UV, white and blue light intensity to 100%, while turning red and far red light down to 60% to achieve the short internodal spacing I desire in the plants.
In the first 2 to 3 weeks of flowering, often referred to as preflower, the plant grows in many respects. The goal of growers here should be to foster overall bud site growth while simultaneously limiting the plants stretching during this stage, a symptom often referred to as the “flowering stretch”. The issue here is that switching to a light spectrum that favors red light in order to promote bud growth also promotes stem growth in cannabis plants. While some stem growth is to be expected, and is desired in some respects, too much stem growth is not a good thing.
HID light users don’t have much options here. Switching to a high pressure sodium light will give the spectrum output you desire for the flowering stage but will also result in some of the stretching associated with the preflower sub-stage. Fluorescent light users, spectrum optimization is impossible, as this lighting was never really meant to grow plants in the first place, let alone flowering plants. You will likely see heavy stretching and low yields. LED users, again if you opted for a cheap light on Amazon your options here are limited. All you can do is switch the lighting cycle to 12-12 and hope for the best. If you have a grow light with a veg or bloom switch, turn both switches on at this point in the hopes that there is enough blue light spectrum to keep the plants desire to stretch at bay. With a custom spectrum LED like mine, I slowly turn up the red light spectrum intensity rather than have it at full capacity like a veg bloom switch grow light. For instance during vegetative stage I have blue, white and UV light spectrum at 100% intensity, and red and far red light at 60%. Although for the preflowering period I keep the blue, white and UV light settings at 100% to keep the stretch at bay, but ramp up red and far red light to 80% to promote bud site production.
Once your plants have photo-acclimated to the change in lighting cycle and spectrum ratio output, your goal is to provide as much light to the plant and its bud sites as possible. Therefore maintaining a high ratio of red to blue light while still offering up the maximum output potential of your light is the best course of action here.
HID light users are to continue with their high pressure sodium lights, ensuring the light is able to access as many bud sites as possible. There is not much else you can do here in terms of spectrum optimization, though HPS lights are optimal for this sub-stage regardless, so you should be more than happy with the results during this stage of growth. Fluorescent light users, proceed with the same strategy as used during the pre-flower stage. LED users with grow lights that do and do not have veg bloom switches should also continue with maximum lighting output. As for those growers with custom spectrum LED lighting, at this point in my grow I place all spectrum ranges on maximum intensity as well, so as to promote growth in all aspects. Your plants are undergoing some intense biological changes during this stage and will need all the light it can get, regardless of spectrum. Although again a full spectrum range favouring red spectrum light would be best in order to promote as much bud site matter production as possible.
The last few weeks of flowering are arguably the most important in terms of bud matter density, terpene and resin production. Depending what your goals are as a grower, you could want more resin and oils from your plants rather than bud density and smell or taste if you are planning to extract.
During this stage your plant will naturally want to slow its flower matter growth in favour of resin and terpene production, though adjusting your grow light spectrum can force the plant to focus its production efforts in different ways. In fact, throughout the flowering stage you can adjust your spectrum depending on whether you prefer higher levels of resin and oils, or greater yields.
Blue light is synonymous with triggering secondary pigment production in cannabis plants, and therefore while a lower ratio of red to blue light during the flowering and late flowering stages may result in smaller yields, it will also produce more oils and resin for extraction purposes. On the other hand higher ratios of red to blue will result in greater bud production with normal oil production levels.
To this point the growth stage goals approach I have been teaching you to this point changes spectrum ratios for each stage of plant growth as well as each sub-stage within flowering. This approach allows growers to promote the production of resin, oils and bud sites rather than having to choose just one - this results in plants with high yields of buds that look, taste and are more potent than if you were to simply have veg and bloom switch lighting, or no spectrum switch at all.
With HID, Fluorescent and most LED lights growers will have to choose whether they want to produce high oil, resin and terpene production, or promote greater bud site density. This is because the lights or bulbs emit a standard spectrum that cannot be adjusted. Although with custom spectrum LED grow lights each stage of plant growth can be manipulated by adjusting spectrum intensity ratios.
Therefore in this last resin sub stage of flowering growers with custom spectrum lights can drop blue light intensity while maintaining UV, white, red and far red light. This continues to give the plant a full spectrum of light, while the drop in blue light forces the plant to continue bud site production in the last few weeks when it wants to focus on resin production instead. Keeping UV light intensity up provides the far range blue light needed to keep resin production moving while also stimulating plant receptors to promote trichome production in an effort to protect itself from the UV rays. And as we all know, more trichomes means more potent buds.
Hopefully this video captured the importance of spectrum optimization when growing cannabis plants indoors, and how using different lighting intensities, spectrum and bulbs can elicit different responses in your plants. The ability to use spectrum as a tool, and manage plant growth as a result, is a great advantage that all growers should know and learn how to master.
This is especially the case as different strains will have different responses to standardized spectrum outputs, so the ability to customize and adjust spectrum and intensity ratios in order to optimize your yield results on a strain by strain basis is a huge benefit.
So in review,
I hope you found this installment of my course “Growing Cannabis 201: Advanced Grow Tips” useful. For more cannabis related courses or recommendations on the best grow products out there, visit me at indica institute or subscribe to my YouTube channel. If you have any comments or suggestions for a new video, be sure to join the discussion in the comment feed below. Please like and share this video, and as always, thank you for listening!
Hi and welcome to my guide on cannabis plant grow light spectrum, and how to properly use it for the best results at harvest. The objectives of this lesson are to learn what spectrum of light cannabis plants need to thrive, what the growth goals of cannabis plants are at each stage of development, how each light spectrum range affects cannabis plant growth, and how the goals for each stage of cannabis growth can be optimized using the correct light spectrum ratio and intensity levels to manage plant growth patterns.
All links mentioned in this video can be found in the video description, along with a link to Indica Institute where you can find a growing list of cannabis related courses and recommendations on the best products for purchase. I’d also like to give a special thanks to my partners at FourBudz grow equipment for supporting free cannabis education. You can check them out at fourbudz.com.
When creating the optimal environment for growing your cannabis plants indoors, there is no factor that has more of an impact on your yields and the quality of your buds than your lighting. Therefore, knowing the full range of light spectrum and how each nanometer range of light affects your plant is a tool in your greenhouse toolbox that will have immediately noticeable results on your plants.
First off, cannabis plants thrive off of a full spectrum light band, from UVB to Infrared. The ratios and intensity of each light range vary in their benefits for the plant at each stage of growth though, so it’s beneficial to know the effects each range of light has on cannabis plants.
For instance, UVA and UVB have an interesting effect on cannabis plants. Similar to the effects of UV on human skin, UV light rays damage plants, stressing them into producing trichomes in an effort to protect themselves from the rays. This is especially true of UVB and cannabis during the last few weeks of flowering, this is known as the resin substage of flowering. When exposed to low levels of UV light during this stage, cannabis plants have been shown to increase trichome production density by as much as 30%.
So what is the significance of more trichomes? Well, these little mushroom shaped growths found on your buds and sugar leaves contain cannabinoids, and therefore the more of them there are in a given area, the more potent your buds will be. As such, using UVA and UVB spectrum light to increase trichome count on your plants will increase overall cannabinoid density, and therefore the potency of your buds.
Unfortunately, you will find with HID bulbs that UV spectrum light is generally filtered out due to the thick glass walls of the bulb. Fluorescent light spectrum is not optimal for plant growth in the first place, and is noticeable simply based on yields alone. As well, most LED lights do not have UV light, and if they do only the best ones have UVB. Generally assume that the $100 cheap boxes you find on Amazon or any non safety certified LEDs won’t be carrying this vital spectrum range of light.
Moving more into the mid range blue light, this spectrum range promotes shorter internodes and therefore stalkier plants. Stalkier plants are more desirable when growing indoors because the further the bulk of your plant is from your light, the smaller your buds will be as a result. This is because the light becomes less intense the further it has to travel to the bud site, so short condensed plants allow for greater grow light optimization. On the other hand, tall stretched out plants may have decent sized colas, but they lack size and bud density further down the plant as you move away from the light.
Additionally, blue range light regulates seedling growth and promotes vegetative growth, although too much blue light without accompanying full spectrum ranges could result in health problems for your plant, such as leaf edema. Similar to UV spectrum light, though to a lesser extent, blue range light is known to help with terpene and trichome production in the flowering stage, stimulating the secondary pigments of the plant that enhance flavour, colour and fragrance. Contradictory to the effects of red spectrum light, too much blue spectrum light during the flowering and late flowering stages will result in less overall bud density and yields, but greater concentrations of essential oils and theoretically more cannabinoids due to increased trichome production levels.
There is less data on the exact effects of green spectrum range light on cannabis plant growth, as many studies are still generally inconclusive. For instance it was initially thought that green range light wasn’t readily absorbed by chlorophyll plants because it’s poorly absorbed in a chlorophyll solution. Although with further research it turns out that other pigments in the plant do absorb green light and continue on to contribute to plant growth and photosynthesis. The effects of this light is interesting though, as it seems to depend on its intensity and mixture ratios with other spectrum ranges. A little amount of green light and the results tend to mimic the effects of blue range light on plants, creating shorter stems and leaves. A large amount of green light seems to have the opposite effect though, more in line with the effects of far red spectrum light which stretches the plant. The takeaway from this is essentially that green light is beneficial, though in small doses, and in congruence with a full spectrum range of light.
Meanwhile yellow light helps to promote germination and long stems, and a small amount during flowering has been proven to increase production of bud sites and density.
Red range light promotes height growth in plants, especially in the early stages of flowering. The intensity and ratio mixture of light being provided to the plant plays a factor in whether this growth is good or bad - as too much red light in relation to accompanying spectrum bands can cause unwanted stretching. Aside from this, it’s known to promote stem growth, flowering and bud matter production in cannabis plants.
Far range red and infrared light promotes bud production as strongly as red, though if the intensity or ratio mixture in relation to accompanying spectrum band has too much infrared light it can cause unwanted stretching in the plant. This is mainly because while red light is easily absorbed by the plant canopy, far red and infrared light penetrates canopy surfaces. Therefore if there’s a high level of this light being absorbed by your plants, they will think they’re under a competing plant canopy and stretch in an attempt to rise above the competitor plants for survival.
So now that you know how light affects your cannabis plants, it's important that you utilize this information to get the most out of your plants at each stage of growth. While your plants will benefit from a full spectrum range of light throughout its life cycle, knowing what the growth goals of your plants are at each stage, and providing the optimal spectrum to achieve these goals will result in yields and buds that are nothing less than top notch.
For instance during the vegetative stage of growth you should be focused on promoting quick and healthy root growth in your cannabis plants. The best approach would be to foster overall growth in the plants while keeping tight internodal spacing. The advantage to this is your plants will have the structure in place to grow the same yields as taller plants, but because they are more stout your grow lights will be able to reach more bud sites with greater ease and stronger intensity levels. This will lead to larger bud density and higher overall yields.
For those using HID lighting, the use of Metal Halide light bulbs during this stage is optimal. If growing using fluorescent lighting, T5 lighting is great for vegetative growth but can lead to some stretching if not used correctly. For those using LED lighting, many of the cheaper lights on the market do not offer spectrum control and therefore you are out of luck when it comes to growth stage optimization. For those growers that have lights with a veg and bloom switch, the veg option should be used as long as it is not all just blue light. As stated before, too much blue light can lead to health issues with your plant. Optimally, you’d be using an ETL safety certified LED light with custom spectrum control options, like my FourBudz light. This way you can keep a full spectrum of light, but drop red range light intensity in favour of blue to obtain the desired growth results for this stage. During the vegetative stage I turn UV, white and blue light intensity to 100%, while turning red and far red light down to 60% to achieve the short internodal spacing I desire in the plants.
In the first 2 to 3 weeks of flowering, often referred to as preflower, the plant grows in many respects. The goal of growers here should be to foster overall bud site growth while simultaneously limiting the plants stretching during this stage, a symptom often referred to as the “flowering stretch”. The issue here is that switching to a light spectrum that favors red light in order to promote bud growth also promotes stem growth in cannabis plants. While some stem growth is to be expected, and is desired in some respects, too much stem growth is not a good thing.
HID light users don’t have much options here. Switching to a high pressure sodium light will give the spectrum output you desire for the flowering stage but will also result in some of the stretching associated with the preflower sub-stage. Fluorescent light users, spectrum optimization is impossible, as this lighting was never really meant to grow plants in the first place, let alone flowering plants. You will likely see heavy stretching and low yields. LED users, again if you opted for a cheap light on Amazon your options here are limited. All you can do is switch the lighting cycle to 12-12 and hope for the best. If you have a grow light with a veg or bloom switch, turn both switches on at this point in the hopes that there is enough blue light spectrum to keep the plants desire to stretch at bay. With a custom spectrum LED like mine, I slowly turn up the red light spectrum intensity rather than have it at full capacity like a veg bloom switch grow light. For instance during vegetative stage I have blue, white and UV light spectrum at 100% intensity, and red and far red light at 60%. Although for the preflowering period I keep the blue, white and UV light settings at 100% to keep the stretch at bay, but ramp up red and far red light to 80% to promote bud site production.
Once your plants have photo-acclimated to the change in lighting cycle and spectrum ratio output, your goal is to provide as much light to the plant and its bud sites as possible. Therefore maintaining a high ratio of red to blue light while still offering up the maximum output potential of your light is the best course of action here.
HID light users are to continue with their high pressure sodium lights, ensuring the light is able to access as many bud sites as possible. There is not much else you can do here in terms of spectrum optimization, though HPS lights are optimal for this sub-stage regardless, so you should be more than happy with the results during this stage of growth. Fluorescent light users, proceed with the same strategy as used during the pre-flower stage. LED users with grow lights that do and do not have veg bloom switches should also continue with maximum lighting output. As for those growers with custom spectrum LED lighting, at this point in my grow I place all spectrum ranges on maximum intensity as well, so as to promote growth in all aspects. Your plants are undergoing some intense biological changes during this stage and will need all the light it can get, regardless of spectrum. Although again a full spectrum range favouring red spectrum light would be best in order to promote as much bud site matter production as possible.
The last few weeks of flowering are arguably the most important in terms of bud matter density, terpene and resin production. Depending what your goals are as a grower, you could want more resin and oils from your plants rather than bud density and smell or taste if you are planning to extract.
During this stage your plant will naturally want to slow its flower matter growth in favour of resin and terpene production, though adjusting your grow light spectrum can force the plant to focus its production efforts in different ways. In fact, throughout the flowering stage you can adjust your spectrum depending on whether you prefer higher levels of resin and oils, or greater yields.
Blue light is synonymous with triggering secondary pigment production in cannabis plants, and therefore while a lower ratio of red to blue light during the flowering and late flowering stages may result in smaller yields, it will also produce more oils and resin for extraction purposes. On the other hand higher ratios of red to blue will result in greater bud production with normal oil production levels.
To this point the growth stage goals approach I have been teaching you to this point changes spectrum ratios for each stage of plant growth as well as each sub-stage within flowering. This approach allows growers to promote the production of resin, oils and bud sites rather than having to choose just one - this results in plants with high yields of buds that look, taste and are more potent than if you were to simply have veg and bloom switch lighting, or no spectrum switch at all.
With HID, Fluorescent and most LED lights growers will have to choose whether they want to produce high oil, resin and terpene production, or promote greater bud site density. This is because the lights or bulbs emit a standard spectrum that cannot be adjusted. Although with custom spectrum LED grow lights each stage of plant growth can be manipulated by adjusting spectrum intensity ratios.
Therefore in this last resin sub stage of flowering growers with custom spectrum lights can drop blue light intensity while maintaining UV, white, red and far red light. This continues to give the plant a full spectrum of light, while the drop in blue light forces the plant to continue bud site production in the last few weeks when it wants to focus on resin production instead. Keeping UV light intensity up provides the far range blue light needed to keep resin production moving while also stimulating plant receptors to promote trichome production in an effort to protect itself from the UV rays. And as we all know, more trichomes means more potent buds.
Hopefully this video captured the importance of spectrum optimization when growing cannabis plants indoors, and how using different lighting intensities, spectrum and bulbs can elicit different responses in your plants. The ability to use spectrum as a tool, and manage plant growth as a result, is a great advantage that all growers should know and learn how to master.
This is especially the case as different strains will have different responses to standardized spectrum outputs, so the ability to customize and adjust spectrum and intensity ratios in order to optimize your yield results on a strain by strain basis is a huge benefit.
So in review,
- Lighting and light spectrum is the single most impactful factor on yield size and quality when growing indoors
- Cannabis plants benefit from a full spectrum of light, though percentage ratios in favour of blue spectrum light are beneficial during the vegetative stage, and light ratios in favour of red spectrum are beneficial during flowering.
- Different spectrum ranges of light elicit different responses in cannabis plants, so it is beneficial to know how the plant reacts to each range of light so you can manage plant growth efficiently
- The different stages of cannabis plant growth, and even the sub-stages of flowering, require different spectrum ratio mixes. It is therefore important to know the growth stage goals of your plant and provide a custom spectrum that benefits these goals
- Most lights will not offer spectrum customization, which is not optimal for cannabis plants. If using HID lighting, the use of different bulbs at least benefits the plant during overall vegetative and flowering cycles. This is the same with LED lighting that has veg and bloom switches. The most optimal lighting for cannabis growth is lighting that has custom spectrum and intensity settings so growers can cater to strain, growth stage, and growth sub-stage spectrum preferences.
I hope you found this installment of my course “Growing Cannabis 201: Advanced Grow Tips” useful. For more cannabis related courses or recommendations on the best grow products out there, visit me at indica institute or subscribe to my YouTube channel. If you have any comments or suggestions for a new video, be sure to join the discussion in the comment feed below. Please like and share this video, and as always, thank you for listening!
