How To Increase Humidity in Grow Tent: 10 Quick and Easy Ways

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Many say it has to do with your green thumb, but I believe it’s in how you care for your plants. If you decide to grow your herbs and leafy greens in a grow tent, you should consider the level of attention and care it entails. One of the challenges that many indoor growers face is managing the humidity level.

Keeping the ideal humidity level in your grow tent is crucial because it helps promote plant growth, improve harvests, and keep pests and diseases at bay. Younger plants, in particular, require a humid environment.

There are multiple ways to raise humidity levels in your grow tent. But first, you need to consider the size of your mini indoor greenhouse as well as the type of plant you want to grow.

Below, we’ll go through several effective methods for raising humidity in a grow tent and help you get the healthiest, greenest, and most fruitful harvests.

Ideal Humidity Level for Grow Tent

The tent’s relative humidity (RH) varies depending on the type of indoor plants and where they are in the growing stages. Here’s a table that shows how much humidity and temperature your plants may need at each phase:

Growing PhaseHumidity RangeTemperature Range
Seedlings/clones70% – 75%74°F – 78°F
Vegetative50% – 70%70°F – 78°F
Flowering40% – 50%88°F – 75°F
Harvesting45% – 50%65°F – 74°F

Telltale Signs of Low Humidity in Grow Tent

Telltale Signs of Low Humidity in Grow Tent

Growing plants in a tent requires a great deal of attention and monitoring. When the humidity level is too low, your plants may struggle to absorb nutrients and moisture. This can have an effect on both the plant growth and yield.

To check when your tent is running low on humidity, look at your plant’s leaves. If you notice any browning or crisping on the leaves, this is a clear sign of low humidity. Curled and withering leaves and stems are also likely.

Size of Grow Tent Matters

A bigger grow room will definitely require a higher humidity range. The amount of air inside a larger tent increases, requiring more moisture into the air. This also means that you need to install a larger humidifier.

Also, bigger grow tents tend to have greater air circulation and ventilation and this will affect the grow tent humidity levels. The size may also make it harder to seal and insulate than a smaller grow tent. Make sure your humidifier is equipped to handle a larger space.

Monitor Humidity Levels

Monitor Humidity Levels

The ideal grow tent humidity level for plants is hard to achieve. Temperature changes and so does the amount of water vapor in the air. It’s always a good idea to invest in a hygrometer and thermometer to control grow tent humidity levels and temperatures.

You already know what a thermometer does. And, well, a hygrometer measures the amount of water vapor in the air. Some humidifiers feature sensors that turn on the device only when needed or stop when the grow tent achieves a certain humidity level.

How To Increase Humidity in Grow Tent

A grow tent with a good relative humidity range helps create a healthy environment for your plants. Here are tried-and-tested approaches you can try to raise humidity in grow tents.

Add Water Bowls

Dot some bowls full of water around your grow tent, near the vents. The water in the bowl will eventually evaporate, introducing extra moisture into the air. This is the easiest and quickest way to boost the humidity in the tent and you can easily refill the bowls once empty.

Another alternative is to mist the air in the tent. When you do this, naturally, the water droplets will eventually evaporate, raising humidity. You can also mist the leaves and roots of the plants regularly to maintain a steady humidity level.

Hang Wet Towels

Hanging a wet towel will help retain moisture in the air. It’s an easy, temporary, and cost-efficient way to give your tent a boost. Just make sure to keep the towels away from light or any source of heat but near the ventilation.

Place Soaked Sponges in the Tent

One of the best ways to increase the humidity in a grow tent is by soaking sponges and placing them inside. Don’t hang the sponges as you would with wet towels since the water may drip all over your plants, defeating its purpose.

Add Larger Plants

For large grow tents, you can place some larger pants as well. When you add more plants, there will be more moisture is released into the air. And this will help boost the humidity levels in your grow tent.

You can dot them around small growing plants like herbs, but ensure that there’s enough space between them so the larger plants don’t dominate them. If you have a hydroponic tent, which is typically small, this might not work. However, you can get a tent with adjustable height if you haven’t started your project.

Group the Plants Together

Some plants will release some water that the other plants can benefit from, which increases humidity levels with time. Group your plants near enough that they don’t touch each other’s leaves so they’ll have enough space in between to get some light, air, and moisture. Make sure to water spray your plants every now and then.

Cover Plants With Dome Cloches

Cover Plants With Dome Cloches

These are glass or plastic domes/bells with a hole that serves as a mini greenhouse that traps moisture and heat. Bell cloches help create a humid microclimate around your plants. To start, arrange the plants a few inches apart and place the domes over them. Then, open the ventilation hole on top.

Bell cloches are great for growing herbs, and greens like lettuce, arugula, tomatoes, and carrots. You can also wrap them using plastic bags with small holes.

However, you should only use them when absolutely necessary as too much humidity can encourage mold growth on the plants.

Install a Humidifier

Install a Humidifier

Installing a humidifier can help make the indoor temperature feel warmer than it actually is. It’s also the easiest way to increase humidity in your grow tent. If you do install a humidifier for your grow tent, go for one that you can hang in your grow tent (if it has ceiling support).

Humidifiers are handy during the winter when the temperature and humidity are low. The devices release moisture in the air, raising humidity levels and providing your plants with ideal indoor growing conditions.

Depending on the size of your grow tent, you can pick from small home humidifiers and commercial humidifiers. We recommend getting one with automated controls for more convenience. Many models also come with a warm air mist feature, which comes in handy if you’re growing tropical plants.

Set Your Extractor Fan to Low Speed

Proper ventilation is important because it helps you manage the humidity levels in your grow tent. It helps pull and push the moisture into the air and keeps it from drying out. Plus, it keeps fresh air moving between your plants.

To do this, you must set your fans to a lower speed to give your plants just enough fresh air to circulate throughout the grow tent. This is especially crucial during the entire growing process.

If you set the fan to a high speed, your plants won’t have enough time to absorb the water vapor that sits on their leaves because that moisture will dry out quickly. This will make your plants dehydrated, and you’ll know this when they start developing dry, brown leaves.

Reduce Temperature

Cooling your grow tent using an air conditioner will raise water vapor. Some plants can handle cooler temperatures so it will be easier to adjust them accordingly. However, other plants, such as tropical ones do better in higher temperatures, so it’s important that you know what you’re growing.

Note that cool air from the air conditioner sinks at the bottom of a grow tent. When you lower the temperature inside, the moist and warm air will rise to the top, which increases relative humidity levels.

However, this is something that not all gardeners have mastered. Consider installing a hygrometer in the tent and make sure that it’s sealed and well-insulated to maintain a steady temperature.

Remove Half of the Grow Lights

Lighting can generate heat, and too much of it can result in moisture loss. In this case, you need to reduce the number of lights in the grow tent. Fewer lights mean that the temperature in the grow tent will be lower, which will raise humidity levels. Or, you can minimize the number of hours they are on.


How Do I Raise the Humidity in My Grow Tent Without a Humidifier?

If you don’t have a humidifier, one of the easiest ways to increase the humidity in a grow tent is to add some sort of moisture-retaining item inside. You can do this by placing a bowl of water, soaked sponges, or hanging wet towels in the tent. Reducing ventilation will also help keep moisture in the tent.

What Is the Ideal Humidity in a Grow Tent?

Relative humidity levels ranging from 70% during the vegetative stage to 30% during the flowering stage are considered healthy for plants in a grow tent. It can, however, vary depending on the type of plants you are growing.

Remember that humidity levels can shift due to temperature changes, airflow, and water usage. It’s important that you keep a broad range of humidity levels in the tent during the growing process. And this will entail quick and easy control over the humidity levels.


High humidity is crucial for growing plants indoors. It helps them absorb water and nutrients through their roots and leaves, which promotes healthy growth. And while achieving the perfect humidity in your grow tent is almost impossible, there are ways to improve it using humidifiers and moisture-retaining techniques.

Remember to monitor humidity levels on a regular basis and adjust as needed to ensure your plants thrive in their environment. Invest in thermometers and hygrometers if you must.

We hope you’ve found this helpful in giving your grow tent a moisture boost. Feel free to share with us which technique works for you—we’d love to hear it too!

If you have more questions regarding the topic, let us know and we’ll be happy to help you. You may also want to check out our related article covering the greenhouse dehumidification basics and the ideal humidity for a greenhouse. Thanks for reading and good luck!

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