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How to Increase Humidity In Grow Tent – It Is Easy with These 5 Tips!

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Humidity and Grow Tents

Are you an avid gardener? If you want to garden throughout the year, then maintaining a tent is a great option. Grow tents help gardeners by allowing them to control growing conditions.

These tents are made of flexible materials and have a reflective lining on the inside. It helps in retaining the heat inside the tent.

Unfortunately, maintaining the right humidity inside the grow tent is not very simple. I learned this lesson when I found my plants drying out despite my best efforts. I could not figure out how to increase humidity in grow tent!

Low humidity can cause stunted growth and poor development of plants. Most plants need humidity levels at 45 to 75 %. However, at different stages of a plant’s life, it can require more or less humidity.

If you notice that the grow tent’s humidity levels are below 45 % on average, you must take quick steps immediately, or you may end up losing your plants.

The good news is that you can increase humidity in grow tents with just some simple tricks without much hassle.

Why Is Humidity Important?

Humidity is nothing but the quantity of water vapor present in the air of any specific area. To grow tents, we need to measure the relative humidity.

It tells you the percentage of water present in the surrounding air and how much can be present at a specific temperature. We can measure this by using a Hygrometer.

It would be best if you remembered that plants could grow well at various relative humidity levels, however, it will depend on the temperature inside the grow tent.

How To Increase Humidity In Grow Tent TopoGrow Digital Humidity Monitor
TopoGrow Digital Humidity Monitor via

What Happens When Humidity Is Low?

Plants need water is something we all know, but what about humidity? When there is high temperature and less water, it creates dry air.

The plants try and absorb more moisture to offset this drying effect from the roots and are under severe stress. Lower humidity levels can make the roots to absorb more water, and if there are nutrients in the water, this excess may also harm the plant.

Low humidity can also make a plant more prone to getting infected with mildew and other infestations.

Is low humidity killing my strawberries How to Increase Humidity In Grow Tent
Is low humidity killing my strawberries? – via Reddit

Why Is High Humidity Important?

In the beginning, I was not sure about high humidity and was even worried that it may harm my plants. However, with experience, I have learned that a high level of humidity is very good, more so, during the growing phase.

It allows the plants to absorb as much water as they require to survive. Plants mostly take water through their roots, but they also ingest through their leaves and stem. Plants have a better chance to get enough water and grow better if there is higher humidity.

What Are the Suitable Humidity Levels?

The natural humidity levels keep changing, and it is best to change the levels of humidity in a grow tent as well, depending on the various stages of a plant’s life. Watch this video for more information.

  • Seedlings and small saplings require more humidity. Ideally, it should be between 70 % and 75 %. This is the time when the plant’s root system is growing. Keeping higher levels of humidity gives a good chance to the saplings to take roots strongly.
  • Flowering plants require humidity levels between 40 and 50 percent. It gives them a conducive environment to grow well. Slightly lower humidity levels also prevent mildews and mold formation.
  • Plants that have already taken root are best with humidity levels between 50 and 70 percent. Though their roots are already developed, they still take in moisture with their leaves for faster growth.
  • While you are harvesting, it is best to keep the humidity levels between 45 and 50 percent. It will ensure that the produce does not become brittle or dry.

However, it would be best if you remembered that the humidity levels would depend on the relative humidity. So, take time to understand how humidity acts and affect plant growth before increasing or decreasing it.

How to Increase Humidity in Grow Tent?

There are different ways you can tackle the humidity problem. It will depend on your budget and how much effort you are willing to put in.

Small gardeners taking some small steps are enough, but for more advanced gardeners and expensive plants, may need to take some big steps.

I have listed a few courses of action, that you can choose from depending on your requirements.

1. No Cost and DIY Changes

  • Mix Mature Plants With Young Ones – This is one of the easiest things to do. Larger plants respire more and elevate the humidity levels inside a growing area. Don’t overcrowd the tent otherwise; smaller plants may find it challenging to get their light and nutrients.
  • Remove A Few Lights  – It is simple logic. As the temperature increases, humidity levels go down. Fluorescent lights emit heat and can dry a tent. Remove a few lights but also check that there is enough light in the tent.
  • Fan Speed  – Free airflow and proper ventilation are a must for plants to grow well. The fans you use must be set at a moderate speed. If the speed is too high, it can dry the plants, and also it will not allow vapor to settle on the leaves. The low speed will increase humidity levels.
  • Towels and Trays  – A cheap and easy trick to increase humidity. Hang a wet towel near the air inflow. Put trays of water near the plants or near the passive air holes. Wet sponges are also a good option. You can place them near a plant and water will slowly evaporate.
  • Spray Bottle  – Most gardeners have spray bottles. Use it to spray water on the walls of the tent twice every day. This way, the water remains on the surface for a longer time, giving the plants a chance to absorb it.

2. More Expensive Changes

If none of the steps given above work for you, then it is time to look at some other options. The grow tent or room may be quite large, and these DIY hacks are not suitable. You will have to spend some money but believe me; the results are worth it.

  • Add an AC Unit – If you already have an AC in the grow tent, but it is not sufficient, then it is time to either replace it or add another unit. Carefully calculate your requirements based on the weather, tent size, etc. before buying a new AC unit.
  • Soil on The Floor  – If your tent occupies a large area, then you probably have some soil on the floor. You can change this soil with one which has better water retention. You can spread it around the plants and watch the humidity levels go up.
  • Build or Buy A Propagator Set-up  – Using propagator, seedlings, and new shoots are protected well, and the increased humidity helps in their growth. For building a set-up on your own, you need.
  • Adjustable Extractor
  • Built-in thermostat

Let the water flow to the humidifier through a pipe and watch how it creates a cold mist in the tent.

  • Humidifier – If you already don’t have one, you must invest some money to buy a good humidifier.
    • It may solve all humidity problems for you.
    • Keep it working between 50 to 65 percent. It is even better if you get a humidifier that has auto control.
    • Be careful because too much humidity creates its problems.

Humidifier Facts

When we talk about increasing humidity, the first thing which comes to mind is a humidifier. It can increase the moisture content inside any grow area, adding water vapor to the air.

However, humidifiers play a vital role in a plant’s life, especially inside a tent. In a confined area, humidifiers can raise relative humidity, and make it better for the plants.

Depending on the plants and their growth stage, you can achieve the right levels. While choosing a humidifier, keep the following points in mind.

How To Increase Humidity In Grow Tent Honeywell Humidifier
Honeywell Humidifier for Grow Tent via
  • Area To Be Covered – The area and size of the grow tent is important. Select a humidifier which can cover the complete area. It also depends on the humidifying rate and how long it can run. Choose a brand that offers comprehensive and consistent coverage.
  • Size of The Water Tank – Every humidifier comes with a water tank. It would be best if you gave it careful consideration. When it is too small, you will have to refill very often. When it is too big, finding a space for it could be a problem.
  • Settings Available – Ensure that the humidifier has different settings in the device because you may need different mist settings at different times.
  • Safety Features – Safety is of great importance for any electrical device, so it is for a humidifier. Some have an automatic shut-off, which comes into effect as soon as a specific humidity level is reached.

Can High Humidity Be Bad?

Like everything else in life, excess of a good thing can also be harmful! High humidity is suitable for a plant’s growth, but it may cause more harm than good if it gets too high. Extremely high humidity can cause some problems like

  • Allows growth of molds
  • Hampers effective transpiration for the plants
  • Encourages bacterial and other unwanted growth
  • Roots’ ability to absorb water goes down, and they become more passive
  • Clog the stomata and reduce carbon dioxide intake, which they need for photosynthesis


Now you understand that higher levels of humidity in grow tent are conducive for the proper growth of plants. Remember that humidity is connected to other factors like ventilation, light, temperature, and water. So, it is a good idea to monitor all factors and not just humidity.

After going through the information I have shared here, you will be better able to understand how exactly you can increase the humidity levels inside a tent.

You can try different things and see what is the best option for you and your plants. Some of the options are cost-effective, and you can experiment with these initially, to understand what works. I am sure that you will soon find what works well.

Feel free to contact us if you have any queries or doubts. If you find the information useful, please share it with anyone in the same position.

With the tips given here, we are sure that soon you will be watching your plants growing faster in a healthy way.