In a cannabis grow, new and experienced cultivators alike usually focus on the big-picture items like strains, soil, lights, nutrients, containers, and water quality. Important considerations like carbon dioxide (CO2) levels often take a backseat in importance or get ignored altogether. This is unfortunate, because carbon dioxide is an essential component of plant development and growth, and boosting CO2 in your grow room can profoundly impact your production and overall quality. Yield can increase to as much as 20 percent.
As every botany student discovers, CO2 is critical for the rapid growth and sustainability of plants. For the human respiratory system, people inhale air into their lungs, where they utilize oxygen (O) and exhale CO2. Plants operate in a similar but somewhat opposite manner, absorbing CO2 through their stomates (the pores through which plants “breathe”), where they use this carbon dioxide to convert it to sugars and oxygen. They use sugar for energy (growth) and release the oxygen into their environment. The process of photosynthesis relies on carbon dioxide for plant growth. Without photosynthesis and the release of oxygen from plants and trees, humans would perish, and planet earth would cease to function as we know it.
Should You Use CO2 in Your Grow?
Whether or not you should use carbon dioxide supplementation in your grow is something that warrants serious consideration. Carbon dioxide systems range from simple and inexpensive to elaborate and costly. For most grows, from a small personal grow to an elaborate commercial operation, there is usually a way to provide effective CO2 supplementation without breaking the bank.
Before taking the steps to add carbon dioxide supplementation, make sure you’ve mastered the essentials of cannabis cultivation and have at least a few successful grows under your belt. Learn the basics before getting into this more technical aspect of growing.
One of the important things to consider is whether or not you have adequate lighting. Regardless of whether you use high-pressure sodium, LED, or even metal halide, the lights should be functioning at an optimum level—meaning you replace them on a regular basis before they burn out completely. Optimum lighting is essential to photosynthesis and the efficiency with which plants use carbon dioxide. Once you ascertain that your lighting is ideal, you can consider CO2 supplementation.
Keep in mind that, like water and nutrients, too much CO2 in your grow is a bad thing. One of the most common mistakes among beginner and novice growers is the notion that more is better. Providing too much water and fertilizers are the most common mistakes and will have a detrimental effect on your plants. Carbon dioxide is much the same. Too much is bad, while supplementation at the appropriate level is good. Optimum carbon dioxide levels are one of the final steps indoor growers learn to take their cultivation to an advanced level—although quality indoor cannabis can be grown without it.
How Much is Too Much?
Carbon dioxide is measured in parts per million (ppm). The natural CO2 levels naturally occurring in our air hovers at around 400 ppm. Botanical research indicates that once CO2 levels surpass 3,000 ppm, it begins to have a detrimental effect on humans, and at 5,000 ppm, it can be lethal. Plants, on the other hand, can survive and grow in environments with carbon dioxide levels that surpass 10,000 ppm.
When used in combination with good light, CO2 levels at 1,200 to 1,600 ppm or so will significantly increase the growth of your cannabis plants. At these carbon dioxide levels, plants can also tolerate and still thrive at higher temperatures reaching 85 to 95 degrees Fahrenheit.
Carbon dioxide is a heavy gas and will sink to the floor of your grow room, so when providing supplemental CO2, ideally it should come from above the plants. This is easier said than done in some grows, so adequate air circulation from fans is essential. Fans should be a part of every grow anyway, but when using supplemental carbon dioxide their importance is even more significant. Since several supplementation methods provide CO2 from the ground level, running fans at low levels to disperse the gas higher is particularly important.
When using carbon dioxide, you want your grow room to have air circulation and incoming fresh air, but not so much that it allows too much of the CO2 to escape. A sufficiently sealed room will allow your plants to benefit from it, so remember that if too much leakage occurs, the benefits will be minimal or lost altogether.
Most experienced cannabis growers agree that plants benefit from CO2 throughout most of their vegetative growth, from the time they are young seedlings to well into flower mode. Discontinue carbon dioxide supplementation two or three weeks prior to harvest. At this stage, the plants have received virtually all of the benefits that extra carbon dioxide provides. The use of CO2 can fall a week or two before you begin flushing your grow and preparing for harvest and curing.
Methods of Supplying CO2 and Determining Levels
There are several ways of providing carbon dioxide to your plants. The various methods range from simple homemade systems to expensive manufactured equipment.
Some of the most basic carbon dioxide systems include the use of yeast and sugar for fermentation. As the sugar ferments and converts to alcohol (check your local laws to ensure this is allowed in your area), it releases carbon dioxide into the room, providing beneficial carbon dioxide. Another method is to introduce dry ice to the room on a regular basis. Dry ice is frozen carbon dioxide, and as it melts, it converts into CO2 gas. A block of dry ice will take approximately 24 hours to dissolve into gas, so regular replacement of the ice blocks is necessary.
A more efficient way of providing CO2 is investing in tanks. Although this method may seem more expensive, ultimately, it’s more cost effective as well as efficient. You can rent a 20-pound carbon dioxide tank for approximately $140 to $160, and it will last you about two or three grows. When using CO2 tanks for your grow, use a regulator to release it.
When providing CO2, you will want to know its levels in your grow room. This is easily monitored with the use of a meter. A wide variety are available with a number of applications. Obviously, you will want to buy one that’s good for agricultural purposes.
Using carbon dioxide in your cannabis grow will help ensure you’re providing your plants will all the essential ingredients they need for maximum quality and production. Experienced growers often decide the investment in necessary equipment is well worth the cost and effort. Once you’ve mastered the fundamentals of cannabis growing, adding CO2 may be the final step toward mastering your craft. Your plants will appreciate the boost in in energy, and if they could, they’d thank you for it!