How to use CO2 in cannabis grows is one of the many questions that we’re frequently asked. CO2 is essential for cannabis plants and every other plant, as to them CO2 is like oxygen and they need it to survive. Cannabis plants can deal with CO2 levels of up to 600% the amount that there naturally is in the air around us. Basically, it makes their cells multiply much faster, so if you use extra CO2 during the flowering period you’ll get buds that are much thicker than usual which, if done correctly, makes for a much bigger yield.
Here’s a guide on what you should do and the strength of the CO2 in your grow room from the 21 st day of flowering onwards. EC levels apply if you’re growing in hydro or aeroponics. If you want to measure them in soil you’ll need to measure the water that comes out from the bottom of the flowerpot once you’ve watered; if more is needed you can add it in the next watering, and if it’s too high then the next watering should just be water on its own.
CO2 needs to be introduced into your room through a silicone tube, with one outlet per plant near the bottom of the trunk. You can also use a 2m tube to go around the grow area with holes facing the center, towards the plants.
- Day 21 of flowering: Begin with 800 PPM, and keep it at that when the extractor isn’t on. When watering, you’ll need to raise the EC every time to raise the CO2 levels. For this first week you’ll need about 1.7 EC using normal irrigation water.
- Day 24 of flowering: Raise the CO2 to 850 PPM, and the EC to 1.8.
- Day 27 of flowering: CO2 to 900 PPM and EC to 1.9
- Day 29 of flowering: From this day onwards you’ll need to increase both CO2 and EC every two days. 950 PPM and 2.0 EC.
- Day 31 of flowering: 1000 PPM and 2.1 EC.
- Day 33 of flowering: 1050 PPM and 2.2 EC
- Day 35 of flowering: 1100 PPM and 2.3 EC
- Day 37 of flowering: 1150 PPM and 2.4 EC
- Day 39 of flowering: 1200 PPM and 2.5 EC. From this day onwards, increase levels every day.
- Day 40 of flowering: 1250 PPM and 2.6 EC
- Day 41 of flowering: 1300 PPM and 2.7 EC
- Day 42 of flowering: 1350 PPM and 2.8 EC
- Day 43 of flowering: 1400 PPM and 2.9 EC
- Day 44 of flowering: 1450 PPM and 3.0 EC (this is the max EC level)
- Day 45 of flowering: 1500 PPM and 3.0 EC
- Day 46 of flowering: 1550 PPM and 3.0 EC
- Day 47 of flowering: 1600 PPM and 3.0 EC
- Day 48 of flowering: 1650 PPM and 3.0 EC
- Day 49 of flowering: 1700 PPM and 3.0 EC
- Day 50 of flowering: 1750 PPM and 3.0 EC
- Day 51 of flowering: 1800 PPM and 3.0 EC – This is the max CO2 level you can have in your grow room. Continue the rest of the flowering period without raising anything, and make sure to do that root wash 10 days before harvesting.
Once everything’s installed and ready to go, you’ll need to know exactly how to use CO2. Well, it’s used in the flowering period from the 21 st day onwards, once the buds start to take shape and are slowly popping up at the tips of all of the branches. You’ll need to change your air filtration so that the extractor only works for around 15 minutes an hour because if it’s left on it will get rid of all of the CO2 and all of the effort will have been for nothing. You can use another timer to program the CO2 controller so that it doesn’t turn on when the extractor is on. CO2 should only be administered when the lights are on, as the extraction should be on constantly when the lights are off.
If you don’t use CO2 in the right way you could end up with yellowing plants, or long stretched out plants with hardly any buds. You’re going to need to know what you’re doing to implement CO2 correctly. There are many systems that can be used to get more CO2 into your crop; beginner systems that are used as a little extra boost and don’t require much care, and then professional systems that measure the PPM of CO2 that there is in the atmosphere. Professional systems are obviously much more effective and efficient than beginner ones, but they also require more work and attention.
If you have any questions feel free to leave a comment.
You can use any way of dispensing CO2, connected to a CO2 controller that will shut off the flow of CO2 once it reaches a certain level, and open it again once it gets too low. If all you have is a normal CO2 meter, you can still control the CO2 levels by opening and closing a solenoid valve using a timer. (Solenoid valves are valves that are opened and closed with an electromagnetic charge). Whichever kind of system you use, you must know the exact PPM (parts per million) of CO2 in your grow room.
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How to Use CO2 in Cannabis Grows; here's a step by step guide on how to correctly use CO2 to get the most out of your plants.
The CO2 emitted should ideally fall from above the garden, as CO2 is heavy and will sink to the ground. Using fans will help keep the CO2 moving around the room and make it available for more plants to absorb. CO2 should only be emitted during the time that the lights are on; plants photosynthesize while it is dark out.
There are multiple ways to introduce CO2 to your garden, but most methods do not guarantee controlled ppm (parts per million, used to measure CO2 levels in atmosphere). For this reason, it’s important to invest in a quality CO2 setup. If the systems below are too costly or demanding for your space, you may consider holding off on CO2 supplemented grows until you’re ready to make the jump.
Compressed CO2 tanks can be acquired at hydroponic stores, compressed gas facilities, or even home brewing stores. In this case, the CO2 is produced by the manufacturers and is collected and compressed into tanks that can be then made available for purchase. This allows you to introduce controlled quantities of CO2 into your garden via emitters without having to own a CO2 generator. The benefit of this setup is that without a CO2 generator, you’re no longer producing heat when releasing CO2 into your garden. For this reason, compressed CO2 is ideal for smaller grow spaces.
Increasing CO2 levels in your cannabis garden will allow your plants to create more energy – if you provide adequate lighting as well. Again, light is the second requirement to create energy for your plants, meaning you must match your CO2 levels with your lighting. However, before we dive into how this is done, there are a number of other considerations to make before investing in a CO2 system.
Most gardeners have found that when you are producing high-quality light in your garden, a CO2 level of 1,200 to 2,000 ppm will increase the growth of your plant significantly. Additionally, when using CO2 your plants can handle a higher average temperature – around 85-90 degrees Fahrenheit. Be aware that if your CO2 levels are too high for the amount of light or heat generated in the garden, you will see your plants become damaged from excess CO2.
CO2 generators, which look something like patio heaters, produce carbon dioxide by burning propane or natural gases. They can be set up to automatically power on or off when CO2 levels reach a specific ppm. Natural gas or liquid propane are very easy to acquire, but the burning of these gases produces heat which can be difficult to regulate in small grow spaces. Because of this, CO2 generators are better suited for large grow spaces with equipment for climate control.
If you have a handle on the above points, you should be ready to try increasing your yields using added CO2.
- Grow a healthy garden with a quality product
- Prevent and/or treat mold and pest infestations
- Set up a secure, sealed grow space
- Use an adequate high-powered light system
- Utilize quality strain genetics
- Use quality nutrients and growing mediums
CO2 levels in our atmosphere are around 400 ppm. Interestingly, studies show CO2 levels can continually increase plant growth as ppm reach upwards of 10,000. Note that once CO2 is above 3,000 ppm it starts to become dangerous for humans to breathe, and at 5,000 ppm it is considered lethal.
Learn how to add and control CO2 levels in your cannabis garden for stronger plants, increased yields, and the best possible end product.