Help for Your Grow Room: CO2 In A Bag

Help for Your Grow Room: CO2 In A Bag

Plants need carbon dioxide like we need oxygen—all the time. Many indoor growers have found that pumping up the natural CO2 level in the air leads to bigger, more productive plants. Gas-powered CO2 generators can cost $400 or more, which is often beyond the budget of amateur growers. At about $30, CO2 bags are a lower cost alternative. What are they and how do they work? Are they worth it?

Mushrooms and other fungi absorb oxygen from the air and emit carbon dioxide (like humans and most other animals do). CO2 bags are filled with fungi spores growing on a medium, such as a grain. The bags also have a filter through which air enters. CO2 is expelled as the fungi grow.

The manufacturers claim that grow bags can raise the CO2 level in your grow room up to 1,500 parts per million (ppm), compared with the 400 ppm in the air normally. Simply hang the bags above your plants; since CO2 is heavier than air, it will fall to them. Using fans to recirculate the air helps keep CO2 from settling near the floor. A small bag is said to supply about four to six plants.

Reports by growers who have used the bags vary widely, from observations of rapid, lush growth after installing the bags to no results at all. We’re not convinced the bags produce enough of a CO2 boost to be worth buying. If you choose to try them, you might want to look for those with fungi that grow into shiitake or oyster mushrooms after they’re done producing CO2—then you can factor the value of a tasty meal into the cost of the bag.

If the bag doesn’t seem like an appealing deal, you can still increase the CO2 level in your grow room the personal way—talking to your plants. The words won’t mean much but exhaling close to your plants will.