How to increase the humidity in the grow room: short guide

Guide to increasing the humidity in the grow room

Modified on: 20/09/2022

The proper humidity is crucial for growing hemp plants, and professional growers know this well. So, here’s how they keep it at the right level

Like many other plants, Hemp plants are very demanding when it comes to the characteristics of the growing environment. Professional growers know this very well, so they have to be cautious and use various systems and machines to ensure the best possible growing atmosphere.

Plants do not only take up water from their roots, but also from their leaves, which take up moisture from the air. Therefore, the air humidity also influences the amount of additional water that has to be supplied to the plants to keep them in perfect health. 

This means that humidity levels should constantly be monitored because too much moisture can destroy a whole crop.

That is why in this short article, we will look at how best to regulate the humidity in the grow room, but be careful! 

You should also remember that in the UK, hemp cultivation is still illegal and cannot be carried out except in an industrial environment and with specific licences, which authorised producers only hold, so this guide is provided purely for information purposes by us at SensorySeeds, a site specialising in the sale of marijuana seeds for collecting goals.

Let’s look at how humidity is regulated in grow rooms to ensure the remarkable growth of hemp plants.

The proper humidity levels for cultivation

The right levels of humidity in growing marijuana

For hemp plants to grow properly, you need to ensure different humidity levels depending on the stage the plants are at. 

For example:

  • In the germination phase, the humidity should be 70-80%, 
  • in the vegetative phase: 45-60%, 
  • in the flowering phase, it should be 40-50%, lowering further to 40-45% in the last two weeks.

When these levels are not respected, some risks can ruin the harvest. For example, too much moisture can slow down the plant’s growth and cause it to rot. 

On the other hand, if the moisture level is too low, there is the risk of slowing down the plant’s growth in any case and the risk of stressing the leaves. So, how do you keep the humidity levels in the proper range? Let’s see in the next paragraph.

Read also: How to buy certified hemp seeds and avoid rip-offs

How to regulate humidity in your grow room

Luckily for growers, the tools for regulating humidity in a grow room are simple to use and inexpensive. 

You need three primary instruments: the hygrometer, the humidifier, and the dehumidifier. Let’s see them together in detail.


The hygrometer to measure the humidity in the grow room

Despite its high-sounding name, which may suggest something complicated, the hygrometer is an instrument that measures the humidity in a room and displays it on a small screen.


As the name suggests, this is a device that can increase the room’s humidity. It is filled with water and releases it in the form of steam. Some models also have an integrated hygrometer to be operated even more efficiently. In addition, some models can be used alternately, while others operate continuously.

One particular humidifier model is the ultrasonic model, which has a technology that reduces the spray to microscopic droplets so that they are practically invisible to the naked eye. In this way, the droplets are enriched with negative ions, beneficial for the plants.

Read also: Marijuana seed shipment legislation: how to avoid risks?


This may seem to be a contradiction in terms, but in reality, a dehumidifier is necessary to maintain the right balance for hemp plant growth. Some people use ventilation systems, sometimes consisting of simple fans, to lower the humidity of rooms or sheds, but this may not be sufficient in some places.

In some very rainy areas, the humidity reaches up to 60-70%, which could harm the flowering plants. Therefore, many growers decide to install fixed dehumidifiers by doing some masonry work. Still, there are also models with condensate storage containers that do not need to be installed and have a removable reservoir.

To conclude

So, it is clear that hemp growers need to be well-equipped for moisture management and have to use several devices to ensure good growth and harvesting. If you are a hemp lover, you might be interested in collecting hemp seeds. In that case, our online shop is just the thing for you!

Although cultivation is banned in the UK, buying and possessing cannabis seeds for collecting purposes. So, what are you waiting for? Visit our shop and discover the many varieties of seeds available.

Choose from our wide range of quality weed seeds to complete your collection: feminized seeds, auto flower seeds, fast growing weed seeds, there is something for every taste! 

We look forward to seeing you on!