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Does CO2 Increase Marijuana Plant Yields?


co2 cannabis grow room

In the process of chlorophyll photosynthesis CO2 is an essential component. In nature air contains 300 or 400 parts CO2 per million parts and is constantly supplied (by the wind). The marijuana plants take the CO2 out of the air very quick. If the amount of CO2 is reduced by a third, there will not be any photosynthesis so also no growth.

The exhaust system makes sure CO2 comes in with fresh air and gets rid of the warm air with too little CO2 in it. Because CO2 is heavier then O2, most of it is close to the ground. make sure that the fans mix the air so the CO2 can reach the marijuana plants. If you do not add extra CO2 to a closed grow environment it is necessary to continuously let the exhaust and ventilation system work while the lights are on. This will provide good conditions for photosynthesis and thus for development.

Limiting factors:

CO2, temperature, water and fertilizers could all be limiting factors. Not enough of one of the elements could slow the whole development of the marijuana plants down. With a higher level of CO2 in the air, the metabolism of the plant goes faster. If it rises to 1500 ppm, it will have to go with a temperature of 25- 30 degrees Celsius. Also the minimum humidity goes up from 40 to 60% and even the amount of fertilizers changes. If this is all done correctly though, the harvest can be 15 to 25% bigger in the same time (or less!).

If you want a strong marijuana plant with flowers close together and a short growth it is wise to artificially add CO2. This technique is very difficult so only experienced growers should try it.  Download my free marijuana grow bible for more tips about growing marijuana plants.

When to use artificial supplements of CO2:

When you have a heat problem and the exhaust system doesn’t work properly you could try using artificial CO2. Everything accelerates when you do this, so if it’s not strictly necessary. Don’t do this the first few times you grow marijuana. When you are more experienced it can increase productivity and gain time.

CO2: not easy to measure.

The devices you need to measure the CO2- level are very expensive, although there is a chemical measure process but you can only do this once with the equipment: a glass tube divided into degrees and a syringe. The tube is filled with a reactive substance for CO2. The syringe is filled with the air that you want to test. Break the tube at the two ends and attach it to the syringe. The air should flow through the tube and the reactive substance changes color: this indicates the CO2 level.

If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.

Source: ILoveGrowingMarijuana.Com



About Author

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.


  1. I’ve been adding co2 for almost two decades. (I’ve been growing cannabis for over three decades.) It DOES work but one must ensure that the co2 makes it to the plant instead of just being removed by air movement. I only use one co2 bucket (hanging higher than the plants so that the co2 travels downward through the plant area).
    I introduce my fresh air from the bottom of the plants (slightly directed upward) so as to keep the concentration of co2 up in the area of the foliage. This lower fan also is used to strengthen the trunk and branches so it has a two-fold benefit. My air exhaust (via my filter) is located on the opposite side of the closet so as to not pull the co2 from the closet. This airflow arrangement is quite effective. The plants continually are grabbing the co2 (as evidenced by the lush green color and their close node-to-node growth).
    Your plants may need water a bit more in quantity or frequency, reason being that the plants have a more active growth cycle happening.
    With this increased growth cycle, your plants may require a bit more food but be sure NOT to overreact. I upped my feeding by only 10% and everything is fine.
    If you are on the bottom line of what your plants need for lighting, then the co2 will really not benefit them but if you have sufficient or more than sufficient lighting, then you’ll be fine.
    Results? My personal estimation of increased yield is about 20 to 30%, which is a sizeable amount whether one has one plant, five plants or ten plants. Personally, from my five-plant population that is always in the flower room, I gain about 1.5 ounces of bud. With this said, my cost of a bucket for $26 an insignificant cost and is a huge benefit. I get two flowering sessions (20 weeks total) from each bucket in a 5 x 2 x 7 closet. I consider this some of the best money I can invest — proven time and time again.
    If you are not seeing benefit from a co2 bucket within a week, then review your lighting, feeding, water and air. If you make an adjustment to feeding or water, make slight adjustments. Review your airflow. With regards to lighting, well, you can never have too much (unless you have heat issues, and with this said, don’t really count on co2 to address your heat issues…).
    I’m interested in your findings after you have ensured that you have made your arrangement conducive to the additional co2. If you have made the arrangement friendly for the addition of co2, you WILL see and reap the benefits.
    I’ll check this site periodically — not so much for those who have already refined their process, but more so for those who initially embark on this process and take heed to the points I have made above. Just make a slight investment for a $26 or $50 bucket (depending on your room size) and give it a shot. It’s money very, very well spent if you do it right…

  2. Humboldt Star on

    10% Really, thats such a tiny margin for all the trouble. What is the yield really?, how many plants, watts, method. I get 2000 g per 1000w of light, nothing special, 6 plants in 5 gal buckets of pro mix, aact, guano.

  3. Humboldt Star on

    Brewers yeast mixed with water and sugar will create C02. However this is not always needed. I have had very good results without it. Just make sure the plants get a good supply of fresh air

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