Carbon dioxide (CO2) is necessary for the correct performance of the plants, together with water, light or nutrients, because plants need to consume CO2 – in atmospheric air – to provide photosynthesis, and, consequently, their basic vital processes – otherwise, the plant won’t be able to produce energy, unable to develop properly, so, although totally unknown for beginner growers, CO2’s fundamental for professional growing.

Indoor cultivation

Indoor cultivation

Why many people don’t know anything about CO2?

Mainly, atmospheric air contains the necessary CO2 for the correct performance of the plants – otherwise, they would die, so, when outdoor growing, no problems about CO2, and, when indoor growing with artificial light, a good ventilation system’s necessary to expel foul air and to introduce outdoor clean air.

This is very important because plants consume CO2 and expel oxygen, so, without proper ventilation, indoor air gets oxygen-jammed, CO2 levels get lowered and the plants are unable to develop; this isn’t a common problem, because, usually, current growers are concerned about ventilation.

How does CO2 work for Marijuana?

Cannabis uses CO2 and solar light to produce the necessary energy for its basic vital processes. One of these most remarkable processes is photosynthesis, a chemical reaction which happens when the plant receives solar light and extracts CO2 from the air by means of little holes at the bottom of the leaves (stomas); stomas function similarly to skin pores, but they have protective cells able to open and close – these pores regulate water, gas, oxygen (O2) and CO2 absorption in the plant, as well as water and O2 expulsion (kind of entrance/exit doors of the plant).

Then, CO2’s absorbed by the strain, heading it to the chloroplasts – organelles of the plant containing chlorophyll which absorbs light, providing photosynthesis; for more info on photosynthesis, check our posts on dark phase and light phase and discover all about this complex process of chemical reactions happening in our strains (basically, photosynthesis absorbs light, water and CO2, producing sugar to feed the plant, expelling oxygen).

photosynthesis process

photosynthesis process

Ideal CO2 levels for growing Weed

CO2 level in the air has a strong effect on photosynthesis and marijuana plant development – photosynthesis process gets boosted as air CO2 level increases (with proper solar/artificial light level).

Photosynthesis lowers down – and almost stops – if air CO2 concentration goes down to 200 ppm; this low CO2 level blocks the plant, because it can’t produce the necessary sugar level for its proper development. The main consequence of this situation’s a blocked growing, because the plant diminishes its metabolism to preserve energy and be able to survive – strains will be able to deal with their vital processes when having enough CO2. Besides, light, temperature and CO2 levels have to be increased for the plant to use the resources properly.

Under CO2 100 ppm, there’s no photosynthesis, and plants have a net sugar loss due to breathing; with CO2 100 ppm, breathing and photosynthesis are similar (no net loss/gain), and, with 400 ppm levels (atmospheric air), photosynthesis increases fast, similarly to the increase of CO2 levels.

The increase of photosynthesis diminishes when CO2 concentration goes up to 800 ppm and, if higher (800-1200 ppm), the increase is more remarkable.

How to maintain optimum CO2 parameters

As previously mentioned, good ventilation – providing fresh, clean, outdoor air to our indoor growth – is the best way to maintain the necessary CO2 levels for proper strain development – fans improve air flow too, as well as CO2 levels.

How to dispense CO2 to our growth

Usually, growers use CO2 tanks which expel gas gradually; generally, these tanks have a full kit – CO2 meters, press regulator, solenoid valve: Grow Shops provide a wide range of articles to generate CO2 for growths.

co2 tank and generator

co2 tank and generator

On the other hand, there are CO2 generators – burning propane or natural gas, they produce the necessary CO2 for marijuana growing; other growers use dry ice (when evaporated, it expels CO2 too).

With little growing space, bicarbonate and vinegar can be a good solution.

How to calculate necessary CO2 level for growing

An example’s the best way to explain it; a 3 x 4 x 3 m room (long x wide x tall) contains 36 cubic meters, and it would require 0.036 cubic meters of CO2: with this simple formula, you can rapidly calculate the exact CO2 level your strains need for proper developing.

Is CO2 dangerous?

Average CO2 level’s not dangerous and, besides, it’s not flammable/toxic gas – with CO2 up to 50,000 ppm, it can be dangerous for our body; anyway, these levels are overrated, and this situation’s difficult to reach – 50,000 ppm’s a proportion 30 times bigger than the maximum percentage needed by a plant.

non-flammable and non-toxic co2

non-flammable and non-toxic co2

CO2 and light intensity?

CO2 levels are closely related to light intensity – main photosynthesis level increase happens when CO2 level goes 0-200.

If light’s dim (150 moles or 1,150 fc) (12,330 lux), photosynthesis level increases when CO2 goes up to 400 ppm; if CO2 concentration’s increased beyond those percentages without increasing light intensity, there won’t be any higher photosynthesis level – in fact, strains are unable to profit the highest CO2 levels till light intensity increases.

If light intensity’s 600 moles (4,600 fc) (49,310 lux), photosynthesis level increases as CO2 levels go up to 400 ppm; increase level diminishes slightly after that, but photosynthesis level keeps increasing as CO2 levels go up to 600 ppm.

If 600 ppm of CO2 are surpassed, photosynthesis level keeps increasing, but even slower, till increasing level stabilizes around 1,200 ppm – if the plants get 4,500-5,500 fc (48,240 lux) of light, the can use up to 1200-1300 ppm of CO2. This way, lumens are necessary to calculate the CO2 level to be provided to our indoor growth.

Homemade and cheap CO2 Dispenser for Cannabis grows

This has been an overview on all about CO2 and marijuana growing – if still in doubt, just leave your comment and we’ll answer as soon as possible.

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