USING LIGHT SPECTRUM FOR HIGHER YIELDS, HIGHER POTENCY AND BETTER LOOKING, TASTING AND SMELLING BUDS.
While there is still many unknowns about cannabis and cannabinoids due to its prohibition and lack of studies as a result, more and more studies about its growth patterns and optimal conditions have been popping up in the past 10-15 years. The result of this gathered information brings forward an issue that has long been recognized by cannabis growers - most grow lights and the spectrum ranges they offer force a trade off between dense high yielding buds that are average in their look, smell and cannabinoid density, or average yielding buds that are beautiful, fragrant, and can have up to 30% more cannabinoid density. In this article I will outline (a) the benefits of different ranges of light on cannabis plants, (b) grow lights, optimal yield results, and the spectrum trade off, and (c) what lights offer the best buds in terms of yield, look, potency, taste and smell. By the end of the article you will know what you need to do to optimize both flower growth and cannabinoid density in order to grow top shelf dispensary level buds.
A. The Benefits Of Different Spectrum Ranges On Cannabis Plants
The following paragraph may be a lot for some readers, but hang in there, I’ll summarize!
Yellow and white light is a commonly used light range for growing plants in general, and in cannabis this spectrum range promotes germination and long stems. During flowering a small level of this type of light can also boost flower production.
Of all the spectrum ranges, the least is known on the effects of green light on cannabis plants, though the consensus is that it is beneficial to have at least a small amount. The common theories are that green light reflects off the plant canopy and into the shadowy areas and backside of plant foliage. It is also believed to counter most of the effects of blue light during the plants vegetative stage.
It is fairly common knowledge that red and far red spectrum light promotes flower growth during this stage, and that blue range light during the vegetative stage promotes stem and healthy root growth. What is less known is that too high a ratio of red-to-blue light during the vegetative stage can cause unwanted stretching in your plants and if this ratio is too low during flowering it will result in lower yields.
Inversely, if the ratio of red-to-blue light is lower during vegetative it promotes shorter, stouter plant growth with tight inter-nodal spacing - ideal for indoor growers. A high ratio of red-to-blue during flowering promotes greater bud production and height growth. Note that too much far red or infrared light during this stage could lead to unwanted stretching.
Lastly, in recent years much has been learned on the effects of blue, UVA and UVB spectrum light on cannabis growth. For instance exposing the plant to greater ratios of blue light during flowering is believed to increase the density of flavonoids, terpenes and cannabinoids. Meanwhile exposing the plant to UVB light, for instance in the last 3-5 weeks of flowering, can result in an increase in trichome production and therefore greater overall production of these compounds by up to 30%.
SUMMARY: There are two important points to take away from all of this. One, similar to how solar light intensity changes with the seasons, your cannabis plants require different intensities and ratios of light during each stage of growth in order to produce optimal results; and two, the resulting effects of red versus blue spectrum light on the plant during the flowering stage are conflicting. A high ratio of red-to-blue light results in high yields but less essential compounds, while lower ratios of red-to-blue promotes greater essential compound density but less overall flower density and yield. This is the cannabis ‘spectrum trade off’ and leads me to the second part of this article.
B. The Issue With Modern Grow Lights: Tackling The Spectrum Trade Off
Today’s grow lights are fairly rigid in their design and use. Most offer up a single spectrum designed to be used throughout each stage of plant growth, with directions to raise or lower the entire light in order to adjust intensity, but this does not change the spectrum ratio at all. This is not ideal because of the contradicting effects red and blue spectrum light has on the plant at each stage. Essentially the lighting company has made the decision of what your goals are for your grow: high yields, good looking and smelling buds, or potency.
Alternatively, some other lighting companies offer up spectrum customization in the form of veg and bloom on/off switches. This brings up a whole other set of issues- for instance too low a ratio of red-to-blue light can slow plant metabolism leading to less foliage and therefore reduced levels of photosynthesis, and can lead to a bunch of other developmental issues such as leaf edema (when the leaves swell up). Most growers with these switches have them both active for most of their grow, leading back to the trade off issue.
Lastly, and what I will be discussing in the next section of the article, is a rare third group of grow lights that have light intensity and spectrum adjusters. These options allow for complete control over both spectrum and intensity without the need to turn a certain spectrum range off completely. There are not many of these lights out there, but they are certainly the future of grow lights as we learn more about what this plant needs to produce the best quality buds possible.
C. The Solution For Optimal Yields And Peak Cannabinoid, Flavonoid and Terpene Production
What cannabis growers need is a light that allows spectrum ratios to be controlled in order to optimize the goals of each stage of growth. There are very few lights like this, but they do exist and are called hybrid, or custom spectrum grow lights. The ones I know about are the KIND K5 series and FOURBUDZ pro series, each offering 4 channel settings that control a different spectrum range. The price difference is notable, even though the lights are actually very comparable - I use a FourBudz pro3 for this reason. I’ll explain the benefits of custom spectrum lighting by explaining how I use it to grow my plants.
When my plants are seedlings, my goal is to promote healthy root and stem growth while avoiding stretching or photobleaching. So for this stage I turn the intensity of blue light and UV light to 30% and red to 15%, then double these numbers after about a week or so.
Once the plant has reached the vegetative stage it can handle full intensity blue spectrum light, but I still keep both red range light channels at 60% to promote more compact internodes and less potential stretching caused by too much infrared light. The level of red light still balances out plant metabolism to keep photosynthesis levels high.
Once I switch to a 12-12 lighting schedule I will ramp up red light intensity to 80% and keep blue and UV light at 100%. This ensures a comfortable photoacclimation of the plant to a full intensity light schedule.
A few weeks into the 12-12 switch I will turn the grow light up to 100% intensity for all channels. The plant is working overtime during this period of growth and needs energy from any spectrum range it can get.
In the last stage, and arguably the most important stage in terms of light spectrum ratios, I keep all reds at 100% to keep flower production levels high. I also keep UV and white light at 100%, which forces the plant to create new trichomes and therefore generate more cannabinods, terpenes and flavonoids. Lastly, I turn mid-range blue spectrum light down to 70%, which adjusts the spectrum slightly to promote greater growth and density of the plants flowers. All in all, this leads to high yields AND high potency in buds that look, smell and taste like top shelf dispensary product.
I hope you hung on and read the article in its entirety. It can be a lot for those new to growing, but lighting is also the single most effective factor in manipulating harvests and creating high yielding top shelf buds. If you just skipped to the conclusion, maybe you’re one of the many growers that simply does not care how top shelf buds occur- but rather that they do with your plants (Just tell me what I need to do!). If that is you, then the bottom line here is go out and buy a custom spectrum grow light. There are a few companies that offer them, like KIND and FOURBUDZ, and they typically come with guides on how to adjust channels at each stage of growth for optimal harvest results. I was able to get the spectrum settings I discussed above from the FOURBUDZ website (click here to view), and the harvest results so far speak for themselves. Click here for a link to the FOURBUDZ pro3 product description.
Growing indoors has been gaining popularity as governments have slowly begun to legalize the recreational and medicinal cultivation of cannabis. Though if you are new to the venture, you are likely among the majority who are simply unsure of what equipment to use, where to get it, and how many plants your equipment will allow you to grow. Choosing a grow tent size is the beginning of your success as a personal grower, and there are several factors you need to consider before hastily buying a grow tent on Amazon because of a ‘hot sale.’ The biggest considerations you will have are the dimensions of your grow space, what plants (or strains) you will be growing, what kind of yields you are expecting, what kind of lighting you plan to purchase and what style of plant training you will be using. Let’s take a look at each of these considerations separately.
1. The Dimensions of your grow space
Don’t assume that just because you have a 2x4 foot closet space to grow that you should buy a tent this size. First of all, the tent sizes listed online are often rounded estimates based on a conversion from centimeter dimensions. The tent that arrives at your door very well could be larger than the space you expected it to fit in. Secondly, even if the tent is actually 2x4 foot, this will still not fare well in a 2x4 foot space. Why? This is because a large component of growing indoors is ensuring you are fostering the proper environment for your plants, and this includes airflow. Passive air inlets and ventilation ports on a grow tent are found at the sides and back of the tent. Therefore if you place a 2x4 tent in an equal sized space these airflow ports will be right up against your wall. Unless you plan to do some construction to your house to allow for proper airflow intake and ventilation, this is a recipe for failure. Expect to need a square foot of space outside your tent for a ducting system to exit your exhaust port. A 2x3 tent in your 2x4 foot space will suffice, so long as your inlet and exhaust ports are at the side of your tent allowing for proper airflow throughout.
2. What plants (or cannabis strains) are you growing?
Another thing to consider is what kind of plants you will be growing, or alternatively, what strain of cannabis you will be growing. Plant types vary in their height and girth and therefore knowledge of how much space each plant will take up is a necessary component to ensuring you get the right sized tent. If you are growing cannabis, different strains will grow very differently. Some will be short and stout, while others could be very tall and lanky. Once you determine what strain you will be growing do some research to figure out its growth patterns before purchasing a grow tent. Even if you have the space for a large grow, determining this will help ensure the right sized tent so it is easier to control environmental factors within the tent.
3. What kind of yields are you expecting?
Depending on why you are growing, whether it be as a hobby, medicinal cannabis use, or just for occasional recreational use determining how much yield you expect to have at harvest is going to be a large factor in how much plants you will need to grow, and therefore how large a grow tent you will need. The more yields you expect the more plants you will need, and therefore the larger tent you should have. As mentioned in the previous paragraph, what strain you will be growing will also affect how much space you will need per plant. In addition to this, you will need to consider what training styles you will be using. Generally speaking, the more invasive the training, the more yields you will generate - but this also means your plant will take up more space in your tent as a result. This leads us to your next consideration...
4. What training style will you be using?
When growing cannabis it is pretty essential to properly train your plants in order to optimize light and space for the best possible yields at harvest. Some training styles take much more space per plant to properly utilize, so it is important to not only understand the strains typical growing patterns, but also to manage space in advance to prepare for how much room they will need once adult training is in full effect. Growers have plenty of training options, and each have their own benefits and drawbacks depending on what your grow needs are. Low stress training like bend and secure are the basics of plant training and tend to require less space per plant, while a technique like screen of green or “topping” tend to take twice or sometimes three times as much space per plant. A general rule of thumb would be:
Training Style: Plants per square meter
Low Stress: ~4
Screen of Green: ~1
Pruning (Topping, Pinching): ~1
Sea of Green: ~4-16 (depending on vegetative cycle timeline)
As you can see from this breakdown, the space you will need per plant varies drastically depending on the training style you plan to implement. It’s therefore important to plan ahead and consider this before purchasing a grow tent.
5. What kind of lighting will you be using?
You’re probably wondering how your light would affect the decision of what grow tent you should buy. Simply put, the strength and coverage area of your lighting is the most important thing that needs to be considered when growing indoors and to obtain adequate yields that you can be proud of. What you will need to consider is how much money you have to spend on a light, how far the light should be from your plant canopy during the flowering stage, and what the coverage area the light will have at this distance. Most of your money will be spent on a good lighting system for your grow space, so determine what the coverage area is for the light, then buy a tent that matches this. Let’s look at the FourBudz pro3 640 watt light as an example.
This light has optimal power to support bud growth during the flowering stage, though it must be just under 3 feet from plant canopy during this stage, covering about a 2.5-3 square foot area. If the light is placed any higher for a larger coverage area, your yields will begin to suffer. Therefore if you have enough for only one pro3 light, your tent should not be any larger than 3 square feet or the reflective mylar walls will be rendered useless and your yields will suffer heavily.
With these considerations laid out, you are now ready to make a decision on what sized tent you will need to buy for your grow. Your next step is making sure the tent you get has the features of a good tent. There are many out there, and some are notably better than the competition. On the other hand, others can have all the features you need and more, but are overpriced due to brand marketing and other factors. To learn about tent features to look for, my article “9 things to look for when buying a grow tent” will demystify the topic. Be sure to check out my equipment recommendations page as well for a comparison between the top brands on the market in terms of value, price and features.
'Prof' is a professionally trained Canadian teacher with a love of horticulture and advocate of the democratization of cannabis cultivation, especially for medicinal purposes.