How to Increase Humidity in a Grow Tent?

How To Increase Humidity In Grow Tent

Growing your plants inside a grow tent is quite a challenging task as you need to ensure that everything from the size of the grow tent to the temperature is perfect. Even a small mistake can lead to the entire batch of marijuana plants getting a major hit in their growth! However, the use of grow tents is getting increasingly popular, especially as anti-marijuana laws are being relaxed all over the US and people have begun to grow their own weed. In this article, we will take a closer look at how to increase humidity in a grow tent.

However, before that, one needs to understand what humidity exactly means and why is it important for the plants – especially cannabis plants. We will then look at some of the best methods to increase humidity inside a grow tent, followed by some methods to even reduce the humidity! Humidity is extremely important for healthy growth of marijuana plants and this is why many people prefer to grow their weed indoors inside grow tents rather than outdoors because they have a much better control over the growth when it is done in such a controlled environment. Here’s a closer look:

What is Humidity? 

Before we begin with anything else, it is critical for growers to understand the basic question – what is humidity? In the most basic terms, Humidity is essentially the concentration of water vapor in the atmosphere. The higher the humidity, the sweatier you feel. The lower the humidity, the lesser the water vapor in the atmosphere. This is something which is very important for the growth of plants and particularly the marijuana plants. 

Why is Humidity Important for your Plants? 

In order to understand humidity and its importance for your plants, you need to understand a little bit of plant biology. As important as light, heat and air are for the survival of plants, water also plays a very critical role. For plants to grow (including cannabis, but also other plants such as kava or tobacco), a lot of water is actually absorbed by them through the roots. However, a significant amount of water can also be absorbed by plants via the leaves and the stem. 

When humidity is high inside a grow tent, it basically means that the air is holding more water vapor in it. Plants can use stomata, which are small pores on their leaves to absorb this water vapor and provide water for themselves! Simply speaking, conditions where the humidity around the plants is higher is actually beneficial for the growth of the plant, especially in the stages before flowering begins. 

Humidity and Cannabis: How Much Humidity Do You Need to grow Weed? 

Humidity is important for the growth of all plants but particularly for growing cannabis! This is because when you finally know how to control the humidity levels inside your grow tent, you can increase or decrease the humidity based on your plant’s grow cycle. The basic funda that one needs to know here is that the higher the humidity, the more the plant will absorb water from the leaves and if the humidity levels are lower, the more it will absorb water from the roots. 

Basically, you need to ensure that the humidity levels are higher during the early growth phases but lower during the later growth (Flowering) phase because that is the time that the plant should begin to absorb water from the roots as all the required nutrients that you mix to the soil would then be absorbed properly via the roots. Furthermore, by adjusting the nutrient levels and the humidity, you can also increase resin production – basically giving you a greater amount of control over the kind of ‘high’ that your plant gives you with the creation of extra-potent buds. Hence, understanding how to increase humidity in a grow tent (and even decreasing it) is very important for those looking forward to grow weed!

How to Increase Humidity in a Grow Tent?

Let us now cut straight to the chase: here’s how you can increase humidity in a grow tent.

  • Using Humidifiers: This is the easiest and the best way in which you can generate humidity inside your grow tent (or a grow room). Many people prefer to buy grow tents which have enough room for their plants, but also space for the humidifier to be kept! A humidifier basically extracts a cool mist which allows the plants to consume water directly via their stomata. Based on the size of your grow tent, you might want to adjust the levels of the humidifier to 50% to 65%. However, you must make sure that you control the humidity levels from time to time and use a humidistat which will allow an automatic cut-off once the desired humidity levels are reached.
  • Using Propagators: Now this is something specifically for the very early growth stage of the cannabis plant. Propagators are great for the seedlings and cuttings as they create just the right environment for these young plants to grow and do not even occupy a lot of space. Furthermore they can be kept inside the grow tent so that you can monitor their growth without them taking space away from the other plants.
  • Mixing Large and Small Plants: While many growers tend to believe that when you mix large and small plants together, you are actually compromising on the growth of the smaller plants because the larger ones will be taking away all the light and heat off of the smaller ones. However, that is a myth. There’s a huge benefit here as when the transpiration process takes place, the larger plants emit a large volume of excess water vapor and Carbon DiOxide, allowing the younger plants to ‘feed’ on them.
  • Using Wet Towels Near Air Holes: This is a quick-fix for humidity levels. You can raise humidity levels inside the grow tent by hanging wet towels near air holes. However, while they increase the humidity levels marginally, this is something that needs to be checked time and again as the towels tend to dry up quickly and need to be replaced from time to time. Using a humidifier is a much better solution.
  • Reducing Air Circulation: When we say reducing air circulation increases the humidity levels, we say that with a word of caution – you need to adjust the fan speed from time to time depending on the amount of humidity present inside the grow tent. Reducing air circulation is bound to result in a higher humidity but keeping it that way for long is going to have a negative impact on the growth of the plants and hence it needs to be increased when humidity rises by too much.
  • Increase Water Resources in the Tent: Another way in which humidity levels inside a grow tent can be increased is by increasing the water resources in the tent. This is another ‘quick fix’ sort of a method and we would still prefer using humidifiers but if you don’t want to spend extra money or are really in need of a quick fix for increasing humidity, you might as well consider adding some pots and pans of hot water inside the grow tent kept on the ground along with the plants and the vapor coming out of these pots and pans will cause an increase in humidity.

How to Decrease Humidity in a Grow Tent?

Now that you know how to increase the humidity levels in a grow tent, let us also give a very quick look at decreasing these levels. Many people wonder as to why would someone want to decrease humidity levels – there are two reasons for that. First off, having humidity inside a grow tent is good for the growth of the plants, but having too much humidity is not. An excess amount of water vapor can be damaging to the plants. 

Secondly, you need to adjust the levels of humidity with the changes in the plant’s growth cycle. If your plant is at a stage where it requires more nutrients from the soil, you might just want to decrease the humidity levels as that would result in the plant absorbing more water from the roots and thereby also absorbing nutrients (as mentioned above in why is humidity important for cannabis plants).

So, in order to decrease humidity in a grow tent – you need to do the reverse of everything that you did when you wanted to increase the humidity levels: 

  • Increase the fan speed or the number of fans
  • Use a dehumidifier
  • Use an air conditioner
  • Provide just a limited amount of water to the plants (but not too little)
  • Do not keep any pots and pans full of water in the grow tent
  • Defoliate the plants (reduce the number of leaves but not by too much)


Here are some of the most commonly asked questions when it comes to increasing the humidity levels inside a grow tent.

  • Why is Low Humidity Bad for Plants? 

Low humidity levels are bad for the growth of the plants for multiple reasons. First off, it is because plants use water not only for their growth, but also as a coolant. Hence, if the temperature is warm but the air is dry, the plants will have a hard time transpiring and their vascular structure will get damaged. Plants getting dehydrated leads to the stomata getting closed and once that happens, the plant has a hard time ‘breathing’. Furthermore, when humidity levels are low, plants tend to take more water from the roots and that may lead to an excessive absorption of nutrients that might cause the tips of the leaves to ‘burn out’. Molds might also begin to appear in case of excessively low-humidity conditions.

  • Is it Bad for Plants to Have Too High Humidity?

High levels of humidity are good, but getting the levels to ‘too high’ is going to be detrimental to the growth of the cannabis plants. This is because having very high humidity levels can result in the plants getting oedema which happens when plants absorb more water than they can use – causing in pressure being built up inside the leaves and plant cells begin to burst. 

There’s also the risk of a soft growth in plants when the humidity levels are too high. Moreover, there’s also risks of foliar diseases as well as root diseases happening to the plant. In addition to that, the higher the amount of humidity, the lesser water goes through the roots and the lesser the water goes through roots, the lesser the nutrients go up the plants, resulting in a deficiency in the nutrient content which is important for the plant’s growth, especially in the flowering stages. 


We hope this article helped you in learning about how to increase humidity in a grow tent so that you get to the optimal levels! Too much or too less of anything is bad and humidity is just the prime example of this! Use these techniques while growing weed in your grow tent to ensure proper humidity levels. We also recommend pro-growers to try out playing with the resins and do let us know if it did help in you getting a better ‘high’ with the bud! 

Happy Growing! 


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