Cannabis is a dynamic plant, requiring many unique inputs to thrive. From cannabis nutrients to soil pH and the right light, it takes a laundry list of ingredients to get potent buds and high yields. One of the most important is carbon dioxide (CO2).
CO2 is a naturally occurring element that is produced through processes like combustion, respiration, and decay. The atmosphere has an ambient amount of CO2, and the element is an integral part of life on our planet.
CO2 is crucial in the cannabis plant life cycle, helping to promote growth. At any given time, CO2 levels in the air are around 400 parts per million (ppm). This is enough for cannabis to mature, but since the element is a driving force in plant photosynthesis and nutrient uptake, using CO2 enrichment can have an enormous impact on total plant growth and yield.
Fortunately, cultivators do have several options for boosting CO2 levels in the garden. From generators to biodynamic soils, the industry has developed a variety of ways to generate carbon dioxide. However, it’s important to strike a careful balance since too much CO2 can lead to problems, including an unsafe working environment for grow staff.
Importance of CO2 in plant growth
When light first hits a plant, its stomata open up, and the plant begins to breathe. The stomata take in carbon dioxide from the surrounding air, and with the help of light energy absorbed by pigments like chlorophyll, plants create glucose through a chemical reaction using CO2, water, and light energy. This photosynthesis is key to plant growth.
CO2 supplementation can benefit plants at every stage of the cannabis life cycle, especially when utilizing higher light levels. When using high-intensity lights, it is important to use CO2 supplementation to ensure all of the light energy is available for the plants. CO2 can increase photosynthesis and allow growers to increase light intensity to ensure all of that energy is being used by the plants efficiently, without any waste.
Higher CO2 concentrations increase the ideal temperature for photosynthesis. However, warmer temperatures mean more humidity is required to help maintain an optimal vapor pressure deficit (VPD), which determines how a plant transpires.
Vapor pressure deficit is the relationship between the amount of moisture in the air and the amount of moisture the air can hold at a specific temperature. VPD is the driving force for transpiration because it dictates the rate at which water will move through the plant and into the surrounding atmosphere.
Using CO2 at various stages of the cannabis life cycle
Carbon dioxide needs to vary throughout the life of the cannabis plant. CO2 should be highest during the vegetative stage and early in flowering, although levels should be tapered off during the final weeks before harvest.
- Seedling stage: Maintaining CO2 levels between 600-1200 PPM can increase root growth and plant development, especially with higher light levels. If the CO2 concentration is outside of this range, plant growth will be slow and less vigorous.
- Vegetative stage: As the plant matures and the photosynthesis process becomes more robust, raising CO2 levels to around 800-1500 PPM can support faster and healthier growth. If the CO2 concentration is outside of this range, plant growth will diminish.
- Flowering stage: CO2 levels can be maintained at the same range as the vegetative stage—around 800-1500 PPM. However, careful monitoring is needed as higher CO2 levels can sometimes lead to higher temperatures, which can harm the flowering process.
- Final weeks of flowering: During the last couple of weeks of the flowering phase, it’s recommended to lower CO2 levels back down to around 400-800 PPM. This helps to ensure the plant isn’t taking in too much CO2 and also helps slow down nutrient uptake.
Cultivators should note that too much CO2 may lead to issues. Prolonged exposure to high levels of CO2 can cause nutrient deficiencies. Plants are forced into overdrive, depleting the nutrients from the growing media at a rate that cannot be replenished and cannot produce enough food to sustain themselves. Prolonged exposure to high CO2 levels also creates a dangerous working environment in the garden for staff, so monitors should always be used to ensure no one falls ill or suffers any adverse health effects.
Ways to generate and monitor CO2 in the garden
The most common way to manage CO2 in a garden is by using a CO2 tank and a solenoid valve that is controlled with a timer or a sensor through an integrated control system. With this type of CO2 system, tanks require monitoring and refilling, which can be a costly process.
CO2 burners or generators are another option for injecting CO2 into the garden. These produce CO2 by burning natural gas or propane at variable rates to create a consistent flow of CO2 into the garden. Generators are ideal for large operations because they can produce lots of CO2, but they can be expensive to operate due to the amount of fuel they use. They also require added ventilation due to the byproducts produced from the burning fuel, increasing up-front costs for installation.
Bags containing different chemicals, microbes, or fungi can also be utilized to increase CO2 levels in the garden. These bags are simple to use and do not require electricity. They hang in the garden, and the process that produces the CO2 is regulated by the temperature and humidity of the environment. Green Pad is a product that uses a unique natural combination of carbons and acids that reacts to humidity to release a measured amount of CO2. Simply spray with water to activate. These pads come in various sizes and last around two to three weeks, although some may last much longer.
Monitoring and maintaining the proper CO2 concentration can be accomplished using sensors, tanks, valves, timers, controllers, and several other different methods. Choosing the one that is best for your grow comes down to the size of your garden as well as the amount of fresh air that’s being exchanged in the growing spaces.
Sensors are utilized to monitor and log data in the garden to ensure a consistent concentration is being maintained while lights are on. They can work in tandem with valves and controllers to manage the flow of CO2 into a garden. In less complex systems, simple outlet timers may be used to control the flow. The Pulse Pro is a reliable sensor to monitor CO2 concentration in cannabis cultivation facilities.
CO2: an important building block of cannabis
Understanding how and when plants are using CO2 plays a vital role in optimizing your garden. By managing CO2 and being perceptive to its interaction with other vital growing factors like light, temperature, and humidity, cannabis cultivators can push their plants to reach their full genetic potential.
Producing extra CO2 can boost yields and promote plant health. However, too much of a good thing can also spell disaster. By staying at the proper levels and constantly monitoring the environment, cannabis gardens and the people who tend to them can thrive.