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How to Increase Humidity in Grow Tent: 10 Tips For Indoor Grow Room

If you are wondering about measures on how to increase humidity in grow tent, then this is the right place for you. Humidity is very important to ensure photosynthesis.

Higher humidity in the environment can reduce the evaporation of water from plants, thereby keeping the stomata open.

Lack of humidity in the surrounding air can cause plants to wilt.

Higher humidity can result in a reduction of water usage from the growing medium of the plant.

Therefore, the perfect balance of humidity is crucial for plant growth.

Step By Step Process How to Increase Humidity in Grow Tent

Why is accurate humidity important for indoor plants?

Apart from the mandatory requirements of water and light, humidity is an essential requirement for indoor plants.

Water vapor present in the form of a gaseous and invisible state in the air makes up the humidity in an environment.

You can also think of humidity as the amount of moisture in the air. Humidity influences the requirement of water by a plant and, subsequently, its health.

Plants generally take water and nutrients from roots to the stems and then the leaves through transpiration.

Indoor plants receive low humidity and tend to lose more water due to transpiration.

Lower humidity and higher transpiration could lead to the closing of stomata, thereby resulting in slower photosynthesis.

Ultimately, lower humidity can stump the growth of indoor plants.

The adverse effect of low humidity in grow tents

The adverse effect of lower humidity on the growth of indoor plants arises from the role of humidity in transpiration.

Humidity levels change with fluctuations in air temperature alongside the addition of water vapor in the air due to transpiration.

The right humidity balance helps in addressing various problems such as foliar and root diseases, plant stress, reduction of yield, loss of crop quality, and others. In addition, lower humidity could stunt plant growth.

Due to lower humidity, indoor plants tend to lose more water through transpiration.

Subsequently, the stomata close in order to prevent excessive water loss.

However, this turns into another problem for the plants. Holding back the transpiration process could be responsible for capturing a lot of plant heat.

Subsequently, the leaves start to wilt, and the growth of plants is very difficult. So, it is important to find out how to increase humidity in grow tent for improving the crop quality.

Definition of humidity and ways to measure it

The basic definition of humidity implies water vapor in the air. Water vapor denotes the gaseous state of water.

The measurement of humidity is visible in the three different forms, such as a relative, absolute, and specific.

Absolute is defined as the amount of water vapor in the air, without taking the temperature of the surrounding air into considerations.

The relative humidity is evident in the form of a percentage.

The relative humidity is defined as the amount of water vapor in the air at a particular instance of time, as a percentage of the total amount of water vapor in the air at a given temperature.

Specific humidity is defined as the weight of water vapor in one unit-weight of air., generally expressed as grams of water vapor per kilogram of air.

The basic instrument used for measuring humidity is a hygrometer.

The sling psychrometer is the simplest example of a hygrometer for measuring humidity.

It has two thermometers mounted with a handle attached to a chain. One of the thermometers in the psychrometer is ordinary and is known as the dry bulb thermometer.

The other thermometer comes with a cloth wick over the bulb, thereby earning the name ‘wet-bulb’ thermometer.

The sling psychrometer is one of the important tools in the answers on how to increase humidity for plants.

Let us see how it works to find out how humidity is measured.

The normal thermometer or the ‘dry bulb’ thermometer helps in measuring the actual air temperature. The ‘wet bulb’ thermometer has a wet cloth at its tip.

As the temperature increases, water molecules on the cloth wick of the wet-bulb thermometer start evaporating from the surface.

In this process, the water molecules expel heat, and the reading on the thermometer decreases.

The amount of water vapor in the air influences the rate of evaporation,

At a relative humidity of 100% in the air, water would not evaporate from the wet-bulb, and both thermometers would have similar readings.

A comparison of readings on the two thermometers in the psychrometer can give an impression of relative humidity.

The Right Humidity Levels of Plants (Cloning, Vegetation, Flowering, Harvesting)

One of the essential concerns before thinking about how to increase humidity for plants is finding the right humidity level.

You cannot just keep the humidity high at all stages of a plant’s growth.

As you all know, the perfect balance of humidity is highly essential for ensuring the optimal growth of a plant.

Therefore, you need to find out the right humidity levels of plants in the cloning, vegetation, flowering, and harvesting stages.


Humidity is a crucial environmental factor that influences cloning plants. Clones generally prefer 90 to 100% humidity in the environment in the initial days after cutting from the donor plant.

High humidity is essential for preventing clones from wilting completely by providing moisture in the surrounding air.


Vegetative plants generally have stronger root systems, thereby absorbing more water from the soil.

Therefore, moderate humidity levels are ideal for vegetation plants. The ideal humidity levels in the vegetation stage should be within 50 to 70%.


Plants in the flowering stage require lower humidity levels. Lower humidity levels during the flowering stage can help in avoiding issues such as bud rot, powdery mildew, and mold.

The ideal humidity levels in the flowering stage should be between 40 to 60%.


The final stage or harvesting stage is highly essential when it comes to humidity.

The humidity levels during the harvesting stage should allow the plants to dry but without excess.

The preferred humidity range is 40 to 50% for indoor harvesting plants.

How to Raise The humidity in Grow Tent –The Basic Techniques

01. Lower the surrounding temperature

When the temperature of the air inside a grow tent is high, the air loses capability for retaining water. Cold air can sink to the bottom due to higher density, and the air is comparatively moist.

Here are some of the promising ways to decrease the surrounding temperature for a grow tent.

02. Oscillating Fans

Oscillating fans can help in improving the circulation of air and disperse the heat created by lights.

Strategic placement of buckets of water

You can place buckets of cold water in the grow tent, especially near air vents and passive air holes.

This could help in increasing humidity levels, due to evaporation of water The buckets could work as heat-sink for absorbing heat inside the tent. Interestingly, you could also use ice for this purpose.

03. Control the temperature outside the tent

The control over the heat in the grow tent could also be possible through controlling temperature outside the grow tent.

You can connect the grow tent to an exhaust fan outside to prevent any heat buildup in the tent.

Check out this link to find out more exciting ways to lower the surrounding temperature in a grow tent.

04. Combine the young and mature plants

It is one of the proven answers on how to increase humidity in grow tent. Mature plants and young plants could be mixed together to achieve a rise in humidity.

General assumptions indicate that mixing young and mature plants could result in a disparity in air consumption. As a result, threats to young plants become evident.

However, you could have a sufficient supply of air as a prerequisite for combining young and mature plants. Let us see in the following steps how the process works out for increasing humidity.

  • Mature plants have a highly developed and complex root system that takes water from the soil.
  • Young plants have a faster transpiration rate as compared to the mature plants.
  • Keep in mind that there is no overcrowding of plants.
  • Huddling the young and mature plants in a grow tent would create higher humidity due to the contribution of water from both sources.

05. Buy a humidifier and use

A humidifier can also be one of the interesting answers on how to increase humidity for plants. Even though it may cost you a little bit, the investment is valid for ensuring the growth of your plants in the ideal conditions.

Now, let us see how a humidifier works so that you can find how to use it for increasing humidity in your grow tent.

Fill up the humidifier with water:

The humidifier is fed with water that heats up and evaporates.

Water evaporates from the humidifier:

The vapor escapes to the surrounding environment thereby increasing the humidity of the growth tent

Control humidity levels:

The features for measuring current relative humidity in a humidifier can help in maintaining the balance of humidity.

Connect a dehumidifier to ensure control over humidity levels in the grow tent

Prevent unnecessary damages:

Make sure that the humidifier is placed at a higher spot and don’t place it directly on the floor. As a result, you can prevent any form of water damages in the grow tent.

Check out below this link to find out how humidifiers can help you control humidity in your grow tent!

Increase water sources

You can also try some simple ways to increase the water sources in the grow tent.

The presence of water sources in the grow tent’s environment in the right temperature conditions promotes evaporation and subsequent rise in humidity.

Here are some of the methods you can try to increase water sources in the grow tent.

Wet Sponges:

One of the trusted methods for increasing water sources in a grow tent is placing saturated sponges on growing trays.

Water trays:

Setting up water trays next to air-intake tubes or passive air holes.

Water basins:

Simply place water basins in different parts of the grow tent

Shallow trays filled with water:

Using a shallow tray filled with pebbles, gravel and lava rocks and water can ensure evaporation from a large surface area.

Subsequently, you can find an increase in the relative humidity in the grow tent.

If you are wondering how to get heat for the water to evaporate from the sources, don’t worry!

The heat supplied in the grow tent would be sufficient to ensure a rise in humidity.

06. Use Fan For Cooling

Fans are very important tools when it comes to finding answers on how to raise the humidity in grow tent without a humidifier.

Let us see how to use a fan for increasing humidity in a grow tent.

Install the fan:

Install a fan within the grow tent

Put a large bowl of water:

Place a large container of water facing the fan.

Blow air on the water surface:

Allow the fan to blow air across the water surface in the bowl

As a result, you can find a rise in humidity levels in the grow tent. However, you should also follow certain precautions while using a fan.

Setting the fan speed to its maximum can lead to faster drying of air than usual. Furthermore, the water vapor would not settle on the surface of the leaves for moisture, thereby keeping moisture away from plants.

Therefore, fans should be set at 60% to ensure optimal levels of relative humidity.

07. Buy a propagator or build your own

The propagator is another essential approach to solve the problem of how to raise the humidity in a grow tent without a humidifier.

The propagator is generally a contained space that helps in the germination of seeds. Some propagators also have heating units that help in maintaining a constant temperature.

Terrariums are the perfect examples of propagators that you can use for increasing humidity in a grow tent. Here is how you can create a propagator on your own.

Prepare the foundation:

First of all, clean out the tank and observe it in full light.

Placing the heater:

Place a water heater through holes in the bricks to provide more surface area.

Lower the water heater into the tank.

Fill water in the tank:

Fill the tank with water to a level just above the bricks

Put the seed tray in place:

Place the seed tray inside the tanker and heat up the soil naturally before sowing seeds

Sow the seeds:

Sow the seeds and place the tray on top of bricks in the tank

Monitor temperature:

Place a thermometer in the soil for checking air temperature inside the propagator

You can follow these steps to ensure the best propagator for increasing humidity in your grow tent.

08. Hang wet towels in grow tent

This technique is one of the basic ones that deal with the relationship between surface area and evaporation.

You can place wet towels strategically in your grow tent, especially near incoming air vents and passive air holes.

The incoming air could blow on the wet towels, thereby leading to an increase in evaporation. A large amount of moisture absorbed into the surrounding air with the help of wet towels can increase humidity.

You can set up a rack for wet towels in the growing room. The best thing about using wet towels to increase humidity in a grow tent is a minimal investment.

You don’t have to cut your wallet for investments in a humidifier or a propagator.

However, you should note that the wet towels dry up after a certain period. So, it is imperative to ensure from time to time, that the towels are wet.

09. Spray water using a bottle

Spray bottles are also a great initiative to ensure ideal temp and humidity for grow tent.

Spray bottles can help in finding the most cost-effective approach for increasing humidity in a grow tent.

You can use a spray bottle in the grow tent for increasing humidity in the following ways:

  • Spray water on all plants in the grow room once in the morning and then again in the evening.
  • Spray water on every wall inside the grow room for a healthy rise in humidity levels.

Generally, you would wind up with many choices when it comes to selecting a spray water bottle for your grow tent. Here are some of the notable ones which you can take into consideration.

Pressurized Sprayer Bottle:

These spray bottles are available with a container and a sprayer head. Pressurized sprayer bottles are ideal for small grow tents.

Battery-powered sprayer:

This sprayer does not require manual efforts, and only a few batteries can do the job of spraying water. Battery-powered spray bottles can have a higher capacity with better targeting.

Atomizer or Foggers:

Atomizersor Foggers are the ideal choice for achieving ultra-low volume mist for grow tents. These devices can help in obtaining a refined and formidable increase in humidity in grow tents.

10. Place wet sponges on a plate

As already noted in this discussion, increasing water sources in the grow tent can also help in increasing humidity levels.

It is one of the oldest tricks used by many growers for increasing humidity in grow tents.

The primary goal in the case of such a method is to place water trays in the growth area.

However, the strategic placement of water sources could be a notable obstacle for new growers.

Therefore, you can choose to place wet sponges as an alternative for increasing water sources in the grow tent.

Reasons for the effectiveness of wet sponges

The main reason for using wet sponges is their higher surface area. Sponges absorb a considerable amount of water and could not dry faster like wet towels.

So, placing the wet sponges beside the grow trays in the tent could increase humidity levels around the plant.

Therefore, you find the exact area to place wet sponges alongside warding off any concerns of water damage. Most important of all, the effort required is minimal in this case.


On a concluding note, we can observe the significance of humidity in the growth of indoor plants.

Humidity plays a crucial role in the regulation of two important processes of a plant’s growth i.e., transpiration and photosynthesis.

The lower humidity in growing tents can influence the overall quality of the crop. Also, the need to control the humidity levels in grow tents at different stages of a plant’s growth is also evident.

The various techniques mentioned in this discussion to increase humidity levels in grow tent offer simple approaches.

Use the solutions and find excellent crop quality from your grow tent!

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