Controlling Temperature and Humidity During Your Grow

May 13, 2020

Environmental control is one of the most important basics to nail down in your grow. Fortunately, marijuana is comfortable around the same temperature and humidity that humans love. An easy way to check the temperature is by seeing how you feel—if you are too hot, your plants probably are, too. Although this method works generally, you will eventually want to dial in your humidity and temperature more accurately. You will definitely need a hygrometer/thermometer or two and, depending on where you live, you may need a humidifier or dehumidifier as well. In Missouri, a humidifier is required during the winter while a dehumidifier may be necessary during the summer months. 

Controlling Humidity

Controlling your humidity is necessary to prevent a host of problems. Out of control humidity can cause plants to have problems uptaking nutrients, decrease their speed of growth and even cause mold. You don’t want to spend months taking care of your precious plants only to crack them open and find that they have bud rot. Managing humidity well helps you avoid these problems before they ever start.

Marijuana likes different temperatures and humidity levels throughout its life. Seedlings prefer a warmer, more humid environment, with temperature and humidity gradually decreasing as the plant grows. Seedlings thrive in an environment with 75-85°F with about 70% relative humidity (RH). After a few weeks, the temperature can fall to 70-85°F with a lower humidity, around 40-60% RH. As the plant enters the bloom cycle, you want to keep an especially close eye on humidity and temperature, with temperatures between 65-80°F and about a 40-50% RH.

Controlling Humidity is Easy

Humidity can be controlled through humidifiers and dehumidifiers, depending on how you need your humidity regulated. If these are not available to you, you can raise humidity by misting your plants directly, although this should only be done as a last resort. 

How to Manage Temperature

Temperature can be controlled through several different factors. As we’ve mentioned before, LED lights produce less heat and are easier to manage than HPS lights. How you build your grow room plays a big role in temperature management, too. Your passive intake should be located at the bottom of your tent, drawing cool air in from the outside to circulate below the plants. Your inline fan and carbon filter should be located high above your plants, pulling the rising, hotter air outside the tent. Using one or two clip-on fans throughout your tent can also help keep plants cool and regulated. To have the perfect temperature at all times, you can even purchase a small air conditioner.