If you’ve been doing research on the web or reading some of the guides put out by premier cannabis connoisseurs the world over, then chances are that you have heard of CO2 generators and you may be wondering what all the fuss is about. Your cannabis plants use CO2 during photosynthesis and specifically to build new plant tissue (i.e. stem material, leaves and foliage, etc.) so proper CO2 supplementation will increase your crop’s rate of growth, potentially even doubling it under ideal circumstances.
The goal of CO2 supplementation is to maintain optimal levels of CO2 in your grow room, with CO2 being measured in parts per million (ppm). A simple CO2 meter can be purchased online or in most garden supply and hydroponic stores; the ideal CO2 level for vegetating cannabis is 1500 – 2000 ppm, while opinions are somewhat divided on CO2 supplementation during flowering. Some growers withdraw CO2 supplementation entirely when they commence the flowering stage of growth, while others reduce their CO2 concentration to between 600 – 1500 ppm.
For the stealth grower on a budget a poor man’s CO2 supplementation system can be jerry-rigged by using a 1 gallon milk jug, 1 cup granulated sugar, and 3 tablespoons standard yeast. Fill the milk jug approximately ¾ full with lukewarm water (note: you want the water to be warm enough to dissolve the sugar not hot enough to kill the yeast) and add the sugar. Put the cap on and shake the jug until the sugar is thoroughly dissolved, then add the yeast and mix thoroughly until the yeast has dissolved. Take the cap off and place the milk jug in your grow.
The yeast in the milk jug will produce CO2 while they consume the sugar, which will overflow from the top and spread out around your plants providing them with CO2. An oscillating fan in conjunction with a milk jug CO2 generator is even better. The sugar and yeast mixture within the milk jug will need to be changed approximately every 3 – 5 days.
Alternatively, or additionally, you can spend extra time in your grow room and around your plants, which will naturally supplement them with the CO2 you exhale. Being in close contact with your plants on a daily basis will also enable you quickly spot problems or identify potential issues in your grow, like lighting, nutrient, temperature, mold and bug problems.
A slightly more professional, entry-level CO2 system for a small, concealed grow can be assembled by purchasing a 20 lb. CO2 tank for between $100-$150 and a regulator. A single tank will generally last for one complete grow cycle in a small grow space, and refilling your tank only costs $15-$30 in most locations.
For those with cash to shell out, or growers operating in larger spaces, a more professional CO2 system may be in order. With prices ranging from a few hundred dollars to upwards of several thousand, some of the most reputable manufacturers to consider include Sentinel Horticultural Products, Green Air Products, Sunlight Hydroponics and Harvest Master.
Higher CO2 levels in your grow room will also make things hotter, so additional ventilation and cooling is a necessity whether you are using a poor man’s CO2 generator or a more sophisticated and expensive system, especially if you use HID lights. If you use additional CO2, remember to turn your CO2 off when you turn on your fans to vent the room; if you leave the CO2 running while the fans are on, you’ll just be venting it to the outside.
Finally, many growers withdraw CO2 supplementation during the last 2 – 3 weeks before harvesting, as high CO2 levels can potentially lower the potency of your yield. Since CO2 is used during photosynthesis, remember not to waste your CO2 when the lights are off.