How to Lower Humidity in Grow Tent without Dehumidifier?

Excessive humidity in grow tents can cause mildew, pest attacks, bud rotting, or reduced growth. To fight these situations, you might think of using a dehumidifier, but that will be a costly solution. I will show you how to lower humidity in grow tent without dehumidifier to maintain a suitable situation for your plants to grow.

You can

  • Boost ventilation in the grow tent,
  • Lower the frequency of watering, or
  • Reduce the temperature inside the grow tent

to maintain the perfect humidity for your plants. I will go over these ideas in detail along with some other necessary information. Keep reading.

Why Should You Lower Humidity in Grow Tent?

As you might already know, humidity is the water vapor present in the atmosphere. If the humidity is higher than the tolerable level, your plants will face the following issues.

  • Fungi or Mildew Attacks: High-humidity environments are suitable for fungi or mildew to grow. As a result, your plants will have visible impacts.
  • Bud Rotting: When the humidity is higher than ideal, it will increase the growth of microbes. Buds or other parts of your plants might rot due to these microbes.
  • Low Water Absorption: Plants evaporate the lion’s share of the water they absorb through roots. If the humidity is high, they won’t be able to evaporate water. In turn, their water absorption will be reduced, which will cause poor growth.
  • Low Metabolism: If the humidity level is high, the CO2 (Carbon dioxide) consumption will be reduced drastically. As a result, plants won’t be able to do photosynthesis enough for metabolism.

What Is the Ideal Humidity Level in Grow Tent?

The ideal humidity level may change across different stages of a plant’s life cycle. I would like to break the life cycle into four stages and show you the required humidity level in each stage. Check the following table.

StageIdeal Humidity LevelIdeal Temperature
Early Flowering40-50%65℉
Late Flowering45-50%65℉

Now that you know the optimal level of humidity in different stages of a plant’s life cycle, I will show you how can you decrease humidity in grow tent.

How to Lower Humidity in Grow Tent without Dehumidifier?

Considering you don’t have a dehumidifier, apply the following techniques to keep the humidity level in the ideal condition.

Boost Ventilation in Grow Tent

You might already have ventilation fans set up inside your grow tent. Cranking up the fan speed will blow more air outside. This means the water vapor present in the surrounding air will also get out of the tent and lower the humidity level instantly.

As soon as the saturated air is blown out of the tent, cool air will enter the tent to fill the vacuum. As a result, you will achieve a lower humidity level without spending anything. But remember, this should not be done for longer. Otherwise, the air inside the tent will be too dry.

Lower the Watering Frequency

As I have already mentioned, plants evaporate the maximum of water they absorb through the roots. The amount can go up to 95%. So, if you water plants frequently, they will continue to absorb and evaporate water. It will increase the amount of water vapor in the surrounding air, causing the humidity level to rise.

Also, if there is too much water in the soil, it will get evaporated and increase the humidity level. So, it is the best practice to keep the watering frequency low. Only water your plants when absolutely necessary.

Reduce Temperature in Grow Tent

If you can’t use a moisture absorber in grow tent, keeping the temperature low will help a lot. When you keep the temperature low, the humidity level will remain on the lower side.

You can do this by setting up an air conditioner in the grow tent. But if that’s out of your budget, you can consider using an air cooler. Blow some cool air into the grow tent to decrease the temperature inside the tent.


I will answer a few commonly asked questions here. Check them out.

Is 60% humidity too high for flowering?

The ideal humidity level for the flowering stage is 40-50%. If the humidity is a bit higher than ideal, it might not affect flowering too much. But if the humidity level is higher than 60%, it might damage the flowering stage.

Will mold grow at 55% humidity?

If the humidity level is lower than 55%, mold won’t grow. Mold starts growing when the humidity level crosses 55%.

Can I use rice as a dehumidifier?

You can use rice to absorb some moisture from the atmosphere. But if the grow tent is large, this technique might not be as effective as others. Plus, you will require a lot of rice to absorb so much moisture.

Final Words

High humidity can be deadly for your plants inside a grow tent. Knowing how to lower humidity in grow tent without a dehumidifier will help you keep the humidity level ideal for your plants. This way, you don’t need to invest money in a dehumidifier.

Cooling the air inside the grow tent and reducing the watering frequency will help a lot to lower humidity in grow tent. These methods are completely natural, free of cost, and highly effective in giving your plants the ideal condition to grow. Give them a try.

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