Maximize Your Indoor Cannabis Yields – 9 Easy Steps
Big Colas = Best Colas
Did you recently weigh your first indoor cannabis harvest and feel a bit disappointed with the yields? Maybe you’re a first time indoor cannabis grower trying to plan ahead for maximum yields. These are the type of people I encounter frequently at 420ExpertGuide.
Most people want to toss a grow light in a grow tent and call it a day. I can’t blame them, cannabis is only a plant, right? When you’re growing cannabis indoors and trying to maximize your yields, that’s unfortunately not the case.
The good news is as long as you have a few minutes to read my nine easy steps to maximizing indoor cannabis yields, your chance of success will significantly increase.
Step 1: Optimize Your Growing Environment
Before I get to the more effective methods, I have to make sure you know about these basics first. If your cannabis plants are stressed due to environmental factors being out of whack, your yields will surely be affected. Bringing those factors back in line will help you maximize your indoor cannabis yields before you even start the more significant methods.
Cannabis seeds grow best at 78 degrees Fahrenheit. After the seedling stage, 72 to 76 degrees Fahrenheit is more appropriate. If you’re using CO2, you can allow your grow tent temperature to increase up to 85 degrees Fahrenheit.
Cannabis plants in the seedling and vegetative phase grow best with 60% to 70% humidity. Cannabis plants in the flowering phase grow best with 40% to 60% humidity.
Get yourself a humidifier that’s large enough that you don’t have to refill it every few hours. Also ensure it has a setting for different humidity levels.
Watering cannabis plants properly can be tricky. Younger and smaller plants will need less water, but their needs will increase gradually as their size and age increases.
My recommendation to growers asking me about watering is not to stick to any one schedule, but inspect the soil by sticking your finger inside and water each time its dry below the surface.
Cannabis soil pH should be kept between 6.5 and 7.0. Failure to stay in that range will affect your plants’ ability to uptake nutrients, and thus affect your ability to maximize your indoor cannabis yields! It can also lead to browning of leaves.
A pH of 5.8 to 6.5 is ideal in hydroponic grows. Failure to maintain this range of pH will affect your plants’ ability to uptake nutrients, and thus affect your yields!
Testing and adjusting your soil pH is easy and inexpensive. This all in one kit is perfect for the job.
Proper airflow in your grow tent or grow space will prevent mold and mildew from taking root and affecting your cannabis yields. In addition to your inline fan, you should have an oscillating fan running to maintain proper airflow.
Planter or Grow Bag Size:
Make sure you’re using a minimum 3 gallon planter or grow bag. Grow bags are better because they allow more oxygen into the soil and allow excess moisture to escape. The more room the roots have to grow, the larger your cannabis plant can grow.
Step 2: Topping, Pruning & Training
You can learn more about pruning with this in-depth pruning guide.
Topping and pruning your cannabis plants can help you maximize your yields. The reason growers top their plants is to diffuse growth hormones from branches with less yielding potential to branches with the most yielding potential.
Three Topping/Pruning Methods For Maximum Cannabis Yields:
- For example, cutting off the top two smaller branches on your plant would diffuse extra growth hormones down to the lower, larger branches.
- Supercropping is when you cut a 1-2 inch tip off every branch, excluding the main center stem. This has the same effect of driving hormones lower into the plant.
- Lastly, some growers even choose to prune the lowest 1 to 2 branches because they receive less light. They’d prefer to send those growth hormones up to the top branches that have the most light and yield potential.
When to Top or Prune for Maximum Yields:
You want to get your topping or pruning complete about a month prior to entering the flowering phase. While topping or pruning cannabis diffuse the growth hormones, it also diffuses the flowering hormones. In other words, if you do it too soon before entering the flowering phase, you’ll delay flowering for a week or longer.
Does Pruning Large Cannabis Leaves Increase Yields?
Many growers remove the largest most obstructive leaves on their cannabis plants in hopes of maximizing yields on the lower branches. Is this really a good idea?
Infamous cannabis cultivator Jorge Cervantes argues removing large fan leaves from cannabis plants is not a good idea:
“Plants need all their leaves to produce the maximum amount of chlorophyll and food. Removing leaves slows chlorophyll production, stresses the plant, and stunts its growth. Stress is a growth inhibitor.”
Low Stress Training:
Another great option to maximize light exposure to bud sites is known as Low Stress Training (LST). When you have a plant that’s 4 feet tall, the middle & lower bud sites don’t receive light as strong as the top, resulting in lower yields.
You can begin LST once your plant reaches 6-8 inches in height, or around weeks 2-3 of age. Determining whether the plant is ready to begin LST involves determining whether the main branch is tall enough to bend over and tie down to the side of your planter or grow bag.
The plant has a natural tendency to grow upward towards light, so with time it will readjust so the bent flowering site faces upward again. The smaller unbent branches will continue to grow upward, and those should also be bent and tied once they become large enough.
It’s important to finish LST as soon as you’re able to. The stems harden and are more prone to snapping as the plant ages. A finished product should look something like this:
Here’s a really helpful video on low stress training from a great cannabis YouTube channel, From Seed to Stoned:
Step 3: Molasses & Soil Microbes
Feel free to read my full detailed post about how molasses and soil microbes can help you increase your cannabis yields.
To sum it up, you can use unsulphured blackstrap molasses in combination with soil microbes during the flowering phase to cheaply and effectively maximize your cannabis yields. The molasses acts as food for the soil microbes, which in turn produce CO2 that acts as a supercharger for cannabis plant growth!
A study done using Mammoth P soil microbes while growing cannabis plants found using Mammoth P resulted in 17% larger yields. Had the researchers also used unsulphured blackstrap molasses, which feeds the microbes and enriches the soil, I’m willing to bet the result would have been 20% increased yields or higher.
If you don’t want to use Mammoth P due to the high price, Real Growers Recharge is a less expensive and very popular alternative used by the cannabis growing community.
Step 4: Maximize Your Light Intensity To Maximize Cannabis Yields
Everyone knows light is essential to growing plants. But so many cannabis growers don’t pay attention to the specifics surrounding how much light is actually needed to maximize your indoor cannabis yields.
I wrote a straightforward and in-depth article on the topic here, but I’ll try to summarize the most important aspects of it below.
The scientific name for light intensity is called Photosynthetic Photon Flux Density, and its measured in units known as moles and micromoles (1,000,000 micromoles = 1 mole). Cannabis plants need a certain number of moles of light per day.
How Much Light To Maximize Cannabis Yields:
In order to achieve that you need a grow light that will cover your grow space in intense light from corner to corner. Many cheap grow LED lights claim they cover areas much larger than they are truly good for when it comes to cannabis. You can read my list of the best available grow lights here.
So how much light do you actually need to maximize cannabis yields? A University of Mississippi study attempted to answer exactly that. Here’s what they found:
In view of our results, it is concluded that C. sativa can utilize a fairly high level of PPFD and temperature for its gas and water exchange processes, and can perform much better if grown at ~ 1500 μmol m-2 s-1 PPFD and around 25 to 30 C temperature conditions.
1500 PPFD is very strong and only available through a select number of LED grow lights. But you can maximize your indoor cannabis yields by increasing light strength by any amount, as long as you’re going from a lower intensity to a higher intensity.
Cannabis is a flowering plant, and like other flowering plants, the yield increases linearly as light intensity increases. So even if you replace your cheap 400 PPFD LED grow light with a better 900 PPFD LED grow light, your cannabis yields will still increase dramatically!
Step 5: Upgrade Your Blurple Light To White Spectrum
Light intensity is definitely more important than purple spectrum versus white spectrum. But for those growers looking to squeeze the most yield out of their cannabis plants, I advise you to upgrade your old purple (blurple) LED grow light for a new white spectrum grow light.
Studies have shown white spectrum light to grow 12-16% larger, and better quality plants. I like the Mars Hydro LED grow lights as some of the best bang for your buck white spectrum grow lights, and they even include infrared!
Infrared Light and Cannabis Yields:
Infrared light is present in small amounts in sunlight. Small amounts of infrared spectrum in your grow light can also help you maximize your cannabis yields.
Researchers have found that even though infrared light can damage plants, in small amounts it can help thicken up the stems, activate a sort of immune response that helps defend the plant from disease, and even thicken up the buds!
If you’re looking to buy a new LED grow light, make sure it has some infrared diodes on it as well. Not all grow lights include infrared light, but it can certainly be helpful to those looking to maximize their indoor cannabis yields.
Step 6: Pick the right strain!
Growers often ask me how much yield per plant to expect, and my answer is that I just cant provide a concrete answer to that question. There are too many factors at play.
One factor that greatly affects cannabis yields is the plant strain, or genetics. I’ll list a few large yielding strains below, and also point you to my friends at ILoveGrowingMarijuana where they offer a whole section of extreme high yielding cannabis seeds!
Here are some cannabis strains that have proven to yield well:
- Girl Scout Cookies
- Blue Dream
- Purple Haze
- Amnesia Haze
With that said, the Alaska State Legislature posted this document to their website to help people estimate yields they may get from cannabis plants using different amounts of lighting. These are just estimates and your results may vary.
Step 7: Easy, Affordable CO2
CO2 is a great way to maximize your indoor cannabis yields. With affordable and convenient products like Exhale Homegrown CO2, it’s easier than ever. Throw one bag in your 4x4ft grow tent and you’re good for several months.
One important point about CO2 is cannabis plants only utilize it when they’re under very intense light. So if you’re using cheap / weak grow lights, you may not see the results you expected. Make sure you’re using strong LED grow lights and they’re hanging at the proper level.
CO2 is present at ~400 ppm in fresh air. Most gardeners find 1,200 to 2,000 ppm of CO2 to be an ideal level for significantly increased plant yields. Keep in mind CO2 is dangerous for humans, and levels of 1,000-2,000 ppm while usually safe, can cause complaints of drowsiness. Levels above 2,000 ppm can become toxic. Do not allow levels to increase beyond that point.
CO2 is heavier than air, so you should have an oscillating fan running to circulate it around the tent. Plants only utilize CO2 during photosynthesis, so when your lights are off you can turn off your CO2 tank.
Step 8: Nutrients
Every cannabis grower knows about nutrients. It’s important to make sure you’re applying them correctly. Nutrient toxicity due to overuse can stress out your cannabis plant, which will ultimately prevent you from maximizing your cannabis yields.
I like to use all-in-one nutrient kits, this way my risk of overfeeding any one nutrient is reduced in comparison to feeding individual nutrients. Once you find a good NPK kit, you can add in separate micronutrient supplement like this one to really maximize your yields:
My Weed Minerals is just an example, but this micronutrient supplement contains 62 organic micronutrients. They activate your plant’s genetics during late stage growth in order to produce larger buds and tops.
These minerals are derived from ocean water, but don’t worry, there’s no salt in this cannabis supplement. Approximately 95% is filtered out with the other 5% remaining present as essential chloride nutrients for your plant.
Step 9: Use Larger Grow Bags
A large part of a cannabis plant’s ability to produce buds is based on its ability to uptake enough water and nutrients. If you’re using 3 gallon, or even 5 gallon grow bags or pots, you may be limiting your plant’s growth to a certain point.
If you’re really trying to squeeze every last ounce out of your plants, using CO2, a full nutrient stack, and strong light, it’ll be worthwhile to use a large grow bag. Consider 7 or 10 gallon grow bags so your roots can really expand and take up the amount of water and nutrients needed to push your cannabis plant to the next level.
The reason outdoor plants can grow so large, among other reasons, is that they have unlimited space for roots to grow in the ground. So this is certainly one trick worth exploring indoors. Don’t worry about your plants growing too tall, you’ll be able to top and low stress train (LST) to control height as needed!
Dr. Bruce Bugby on Maximizing Cannabis Yields:
These are tried and true methods for maximizing your indoor cannabis yields. An April 2019 study from McGill University agrees, and found that:
In order to increase cannabis yield per square meter and per W light, the results of this meta-analysis point to the use of (1) low plant density (≤12 plants per square meter), (2) a flowering period duration of 9 weeks, (3) the use of HPS lamps, (4) an adequate fertilizer regime, and (5) manipulating light intensity to preserve high energy efficiency vs. favor THC and CBD accumulation. Furthermore, our results demonstrate that cannabis varieties respond differently to production conditions.
How do I maximize indoor cannabis yields?
There are several methods you can utilize to increase your cannabis yields. They include optimizing your grow environment, increasing light strength, secondary nutrients, topping your plant, and picking a high yielding strain. Read article for details.
Does removing large cannabis leaves increase yields?
Cannabis growers commonly remove large sized leaves in an attempt to increase light exposure to lower branches and increase yields. But infamous grower Jorge Cervantes argues cutting large healthy leaves slows chlorophyll production, stresses the plant, and slows growth.
What’s the highest amount of light cannabis plants can be exposed to while flowering in order to maximize yields?
During the flowering phase, a study from University of Mississippi found that cannabis sativa plants grew best under 1500 micromoles of light, when using supplementary CO2. Without CO2 1100 to 1200 micromoles of light is more appropriate.
What nutrients increase cannabis yields?
Most cannabis growers use primary nutrients, but not all use secondary nutrients. These secondary nutrients can further increase your cannabis yields. Read this article for a list of secondary nutrients.
How long should I wait to harvest cannabis in order to get the largest yields?
A study from McGill University found 9 weeks of flowering to be ideal for the highest cannabis yields, although time to harvest can vary by strain. Make sure not to harvest cannabis too early.
What type of grow light is best for maximum cannabis yields?
As long as the light intensity is the same with each light, and LED grow light would be preferable to an HPS or CMH grow light when it comes to yields. But if your LED grow light isn’t strong enough to produce high yields (1100-1500 micromoles), you should consider an HPS grow light.