How To Increase Humidity In Grow Tent — Simple Steps For Healthier Plants

Indoor gardening presents with its own unique set of challenges. You have the ability to intervene and change conditions to make them ideal for your plants. But then you also have the job to ensure that conditions inside the grow tent stay right for your plants. Controlling humidity is a big part, and a tough one to manage right. Here are some ideas on how to increase humidity in grow tent.

Basics For How To Increase Humidity For Plants In A Grow Tent

To put it rather simply, plants use most of the water they absorb as a coolant. Leaves of most healthy plants are full of moisture. If the relative humidity (RH) of your grow tent is substantially lower, the plant will face high vapor pressure deficit (or VPD). In this case, leaves will start losing moisture to the air, and eventually start drooping. 

Even if you give your plant enough water, it will have to work tremendously hard to stay alive – all the while continuing to lose water to the air. Not the conditions conducive to growth!

Before you begin to get a fix on the problem, it’s important to know the problem. Keep a good quality hygrometer (humidity meter) in your grow tent. Preferably one that also includes a thermometer. If you are going to increase humidity for plants, you might as well be sure of the course of action, rather than rely on guesswork.

Tips On How To Increase Humidity In Grow Tent

Topolite Grow Tent
Image: Topolite 4×4 Grow Tent on Amazon

1. Increase Water Sources

The most intuitive fix to the problem is to increase water sources in your grow tent to up the RH. There are a few ways you can go about this. Place a few basins of water at different points in the grow tent. You could place saturated sponges on growing trays. 

A very popular method is to hang wet towels. They’re just more convenient. You can use white-color towels and hang them near the entrance/openings of the grow tent to reflect light away.

2. Get A Humidifier

You can find a fairly acceptable humidifier at a rather low price. They are convenient and can be an easy quick fix to increasing relative humidity. A problem with humidifiers is that if you let them run, you may end up with too high relative humidity. 

To avoid this problem, you could consider buying a humidifier with humidistat. Once the air reaches the right humidity, the humidistat will cut-off the humidifier. Some setups include a humidistat connected to a humidifier and dehumidifier. The idea is to switch either device in response to the relative humidity in the tent.

3. Lower The Temperature In Your Grow Tent

Keep your grow tent at a temperature that is comfortable to your plants, but keep that temperature as low as you can. In rather crude terms, cooler air offers higher relative humidity as compared to warm air for the same volume of water vapor.

You can achieve a temperature drop by lowering the number of lights in the tent, using white towels at the entrance to reflect light (and heat). While it is an expensive option, you can also use an air-conditioning unit to control temperature and humidity. Some people also make use of swamp coolers to bring down the temperature and increase relative humidity simultaneously.

4. Get A Fan

Good circulation of air can make all the difference. You don’t want to create pockets of high-humidity while other sections of your grow tent struggle with low relative humidity. A fan will circulate air throughout the tent, ensuring there’s good RH everywhere. 

For example, while your humidifier may be doing a great job pumping moisture into the air, it can’t circulate air inside the tent. A fan will ensure the moisture being added reaches every corner.

5. Use Propagators

You can place propagators like Victorian bell cloches over your plants. These can help conserve RH for your plant(s) by shielding them from the larger atmospheric humidity issues.

6. Mix Young And Old Plants

Place a few mature plants near younger plants. Mature plants release more water vapor and can create small zones with better relative humidity for younger plants. Remember to avoid overcrowding and ensure all plants have access to nutrients, air, and light.

Keeping It Simple With Increasing Humidity In Your Grow Tent

Huge swings in relative humidity regularly won’t help your plants grow. Changing RH from 30 to 60 suddenly isn’t very helpful. Instead, try to keep your plants within a healthy humidity range, and shielded from sudden changes in RH. Knowing how to increase humidity in a grow tent means any changes must come gradually, rather than as a shock to the plants.