All plants need CO2, cannabis being no different. Anyone who remembers some basic biology lessons from their secondary education days will recall that all plants require CO2 (carbon dioxide) to make sugars needed for both respiration and growth. Plants breathe in CO2 and emit oxygen through their leaves as part of their photosynthesis process.
At sea level, normal CO2 content in the air generally hovers in the 400 ppm (parts per million) range. Some growers pump additional CO2 into their grow closets to ensure that the CO2 level in their closets isn’t depleted and doesn’t fall beneath that average level critical to proper plant growth.
Other closet growers also add CO2 to their grow spaces to speed up the growth rate during the vegetative stage of development. Some studies and anecdotal information suggests that increasing the CO2 level up to 1700 ppm in a grow space can increase the rate of plant growth by as much as 30%. Higher levels apparently don’t return additional gains.
If you’re considering adding CO2 to your grow space, it’s important to remember that it should only be used during the vegetative (plant growth) stage and not the flowering stage. Higher levels of CO2 during the all-important flowering stage have a negative effect on THC’s chemical development process, and can seriously weaken the potency of your plants.
A standard 25-pound CO2 cylinder used for fountain drink dispensers or beer kegs can be bought online for less than $100; you can probably buy them cheaper locally. You can also control it with an electrical solenoid-operated valve system for another $85 dollars or so, and a $20 digital timer. Adjust the flow rate on the valve to where it’s releasing CO2 in that 1700 ppm range, set your timer up to open the valve for a minute or two every couple of hours, and you can rather inexpensively have a fully automated CO2 booster system for your grow closet.