Does CO2 Speed Up Flowering?

Does CO2 Speed Up Flowering?

CO2 is an essential resource for plants. Outside the plants can access CO2 in its natural distribution. Since there’s no way to enclose the plants, they make do with atmospheric C02 level.  


Atmospheric C02 level is about 400 parts per million (ppm), but the plants need between 1200-1600 ppm to yield more indoors. Thus, adding more C02 to a suitable level can improve yield and potency considerably. 


That deficit might seem a little exaggerated because outdoor cannabis plants won’t use all the C02 in the air, but you’d rather have your plant swimming in C02 than lacking it.


C02 is an essential ingredient in the plant’s food-making process. During photosynthesis, the plant’s cells use carbon dioxide and energy from the sun to make sugar that the plant uses for growth and development.


The more the C02 concentration in the air, the higher the rate of photosynthesis and metabolism, and the faster the plant grows. 


When the plant has enough food supply, it looks healthy and goes through the cycle much faster. When the food is scarce, the plant’s growth stalls, and it might suffer various deficiencies. 


Thus, when your plants can access C02 in abundance, the plant will grow optimally and yield better. 


Does CO2 Speed Up Flowering?

C02 speeds up photosynthesis and quickens the plant’s growth and development. Thus the plants will flower faster, and the buds will mature faster too. But adding C02 to your grow room shouldn’t entitle you to early flowering, still study the trichomes before you harvest.


Growers who supplement C02 do it to boost yields rather than quicken the flowering time. 


Adequate C02 doesn’t dramatically speed up flowering. Most growers report one week earlier harvest, which isn’t a lot of time.


The vigor with which the plant grows when you supplement C02 is worth the trouble. The stems become more robust, the branches grow bigger, and thus more bud sites. When the buds begin to develop, the extra vigorous growth will manifest in more fattened buds.


If you want to hasten the development of your buds and reap bigger, then adding C02 is a better choice to make.


But the plan to increase C02 should be preceded by keeping other growth resources at the optimum. 


Ensure the plant receives enough light of the right intensity, is well-watered, has sufficient air circulation, and has enough nutrients.


If these other factors aren’t tailored to meet the new hike in metabolism, then the added C02 can even hurt the progress of your plants. C02 increases photosynthesis and the metabolism of the plant. If you don’t have adequate lighting to match the high levels of C02, it’s most likely a wasted effort. 

Does Longer Veg Mean Longer Flower?
Most growers add C02 to improve yield, not to shorten flowering time


Does CO2 Shorten Flower Time?

A lot of factors influence how long you flower your plants. The plant’s genetics plays a bigger role as some strains flower faster than others. Adding C02 can reduce flowering by a few days to a week, but you shouldn’t rely on it to reduce your flowering time. Stick to observing the trichomes with a jeweler’s loupe to know when the time is suitable for the cut. 


If the plant was supposed to flower for 70 days, do not hasten the process. If you assume you’re going to harvest earlier because of supplementing C02, then you might sabotage the last stages of the buds’ maturity.


It gets worse when you flush too early as you’ll end up denying the plant the resources they need for the last rush of maturing and potentiating the buds. 


Thus, stick to the flowering period the seed company suggested. Stick to the timelines even after adding C02, and the buds seem bigger and healthier. You shouldn’t interfere with the flowering time.


The best way to reduce the flowering time of your cannabis plants is to begin with strains that flower for a shorter time. That way, you wouldn’t have to interfere with the plant’s natural bud-nurturing process just to flower sooner. 


The problem with prioritizing harvesting sooner is that you lose sight of what’s essential. Yield and potency are what you should be worrying about most of the time. 


Supplement C02 in your grow room to grow bigger buds and achieve a more significant yield. Then allow the buds enough time to mature so that they’re not only big but also potent.


However, if you want to go for a vacation and thinks of using C02 as means to make the buds develop and mature faster, you might not benefit much. 


Note: You shouldn’t supplement C02 at night because the plant will not be carrying out photosynthesis. During the night, the plant respires, giving out carbon dioxide and taking in oxygen; thus, adding more C02 can be detrimental to the plant’s development. 

marijuana co2
Sample grow room carbon supplementation set up. Source:


Frequently Asked Questions About C02 Use In The Grow Room

When Should I Stop Adding CO2 To My Grow Room?

You should stop using C02 three weeks into flowering. Also, you should stop adding if the levels are above 1600 ppm. Like with everything, too much C02 is poisonous. You should begin using C02 when the plants have rooted well. The third week of growth is an excellent time to start using CO2. 

Can Too Much CO2 Kill Plants?

Too much C02 is harmful to the plants and humans operating in the grow room. When the level of c02 reaches 2000, the plants will begin to deteriorate and produce smaller buds, reducing yield. 

How Long Should I Run CO2 During Flowering?

Supplementing C02 will be more rewarding when done during the first 2-3 weeks of flowering. During this time, the plant is stretching and creating new bud sites. The additional C02 is instrumental to this growth. 

In conclusion, adding C02 stimulates photosynthesis and metabolism. It creates an increased growth rate, earlier maturing crops, increased potency, and better yield. 


However, when you increase the level of C02, also ensure the levels of other key growth factors are within the sweet zone of the plant. Light intensity, water, nutrition, and grow room humidity must be at the optimum for the added C02 to make any difference.


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