how to decrease humidity in terrarium

Learning how to decrease humidity in terrarium is crucial when you are a plant lover and want to grow smaller plants at home.

So many smaller plants have a hard time adapting to normal home atmospheres. But the use of terrariums helps those plants adapt and grow with minimal care.

The issue is that your plants would suffer significantly if the temperature and humidity are not at their very best.

Interestingly, higher humidity can be a lot more harmful, which is why you need to know how to lower humidity in terrarium.

You can lower humidity in the terrarium by removing some plants, changing the watering schedule, using charcoal, and so much more. 

What Exactly are Terrariums?

what exactly are terrariums

For some plants, terrariums provide the ideal, contained space. It will be more like a small greenhouse in your home.

Usually made of plastic or glass, you can find two basic types of terrariums, including:

  • Open terrariums
  • Closed terrariums

Whether you have an open or closed terrarium depends mainly on the absence or presence of a cover.

Fact: Terrariums were invented by Dr. Nathaniel Bagshaw Ward in 1829. 

Working Mechanism of Terrariums

As mentioned already, terrariums are like mini greenhouses you keep inside your house. But how do they work?

They work by maintaining proper humidity and recycling water.

The vapor condenses on the inside of the vessel and eventually seeps into the bottom.

miniature greenhouse

As terrariums are self-sufficient, they require very little care as long as the lid is kept on tight.

Most require exposure to light, either directly or indirectly; however, supplemental artificial lighting may be sufficient in some cases.

You can provide your terrarium with one of three distinct lighting sources:

  • Indirect sunlight
  • Direct
  • Artificial sources

Fluorescent and light-emitting diode bulbs are suggested.

But, do not use regular incandescent light bulbs.

Moreover, placing a closed terrarium in sunlight might be harmful to the plants inside if the temperature rises above their ideal range. 

Fact: In the 19th century, terrariums were seen not as a fun DIY activity for a gloomy afternoon, but as a vital industrial instrument in accelerating globalization.

Growing Plants in Terrarium and Humidity

The majority of terrariums’ plants thrive in high humidity.

Keeping the humidity in a terrarium at a steady level will prevent the glass from fogging up too often.

But, sometimes, it can be a bit too high for you to see anything clearly inside the container.

Keeping the humidity at suitable levels is essential to ensure your plants can thrive.

gecko in terrarium

They can withstand much higher levels of humidity than any reptile, including bearded dragons and geckos.

In case, this is your first time constructing a terrarium, try not to overthink it. You are bound to err at some point.

Obviously, everyone does. If you are careful and observant, you will get the hang of it after setting up a few terrariums.   

Types of Plants and Humidity in Terrariums

types of plants and humidity in terrariums

Doing some background reading on the plants you wish to grow is a good piece of general advice.

Not all those plants require the same level of temperature and humidity.

For instance:

  • Closed terrariums with soils that keep moisture, like clay, are great for mosses
  • Open terrariums should be used for succulents, which cannot tolerate high humidity.
  • Rooted plants like the polka dot plant prefer high humidity and need drainage.

How to Decrease Humidity in Terrarium?

terrarium hygrometer

In so many cases, high humidity is a real concern. And to confirm where you stand, it is better to invest in a hygrometer.

The device will help you determine if the humidity is high and when it comes down because of the steps you take to lower it.

Here is a bit about what you can do to decrease humidity in your terrarium: 

Expose It to Fresh Air

Getting rid of excess moisture in the air is quickest when you open some windows.

 It is important to open up closed terrariums from time to time to let in some fresh air. Stop misting open terrariums.

You have to ensure that there is less water in the enclosure to lower humidity.

So, simply take the cover off or leave the lid open for several hours each day. 

If you want to increase airflow in the terrarium, placing a small fan nearby is a good idea.

But do not go crazy, as too much air circulation might kill your plants

Change Watering Schedule

Overwatering is a major contributor to excessive moisture in a terrarium; therefore, you should readjust your watering schedule accordingly.

Carefully monitor how often (or how much) you water your plants.

change watering schedule

It is better to water your plants less frequently and let the soil dry up a little in between watering schedules.

 If you do not want standing water on the surface of your plant containers, it may also be a good idea to water them from below

Take Plants Out

When a terrarium is too crowded, condensation builds up.

The quickest solution is to remove some or reduce the size of the existing plants.

Inevitably, there will be some overgrowth of plants in your terrarium, which makes things harder to manage.

And that is probably the reason why the fast growth rate of the Ficus Benjamina tree makes it unsuitable for terrariums.

Similarly, pruning is necessary for ferns like the Golden Pothos and button ferns to keep them from taking over.

So, know when to prune or even remove plants to maintain humidity.

Fact: In an open terrarium, decreasing the air temperature is the quickest way to reduce humidity. 

Use Charcoal

use of charcoal in terrarium

The bottom of your terrarium could benefit from some charcoal or gravel to help absorb any excess moisture.

Doing so will establish a drainage layer and stop liquid from pooling at the container’s base.

Another upside is avoiding mold and mildew because charcoal has antibacterial and antifungal capabilities

Change Temperature

A good way to control humidity is to alter the temperature in your terrarium.

You need to increase the temperature using a heating pad or a lamp. Alternatively, you can place it in a warmer room.

Just understand that you do not want to expose your plants to excessive heat or it will prove counterproductive. 

Important Factors Affecting Humidity in Terrarium

factors affecting humidity in terrarium

You have to pay attention to how often you water your plants as well as the temperature within the container.

But, many other factors play a role here:

Substrates Affecting Humidity

Terrarium substrates are highly variable.

For instance, normal potting soil can be used to grow moss in a terrarium, despite the plant’s high water needs.

But, succulents need a terrarium with a sand or gravel floor to trap moisture for the plants.

Water absorbed and stored by substrates causes an increase in the ambient relative humidity.

Similarly, succulents need a closed environment, whereas moss can survive in an open terrarium.

Even though the soil is wet, the relative humidity may not be optimal, so you have to keep an eye on it. 

Changing Humidity with Water

changing humidity with water

It is not recommended to water damp substrates (which could lead to mold or fungal growth), so a water dish should be placed within the terrarium instead.

Humidity rises more rapidly as the bowl’s contents fill with water and as the room’s temperature rises.

As expected, removing the water bowl reduces the humidity once it has been artificially increased.

The terrarium needs to be cooled and ventilated so that the surplus water may evaporate.

Fact: It is difficult to pinpoint the precise time and place when the term "terrarium" first appeared, as they were originally called Wardian Cases.

How to Know If Humidity is Too Low in Terrarium?

know if humidity is low in terrarium

Just like too much humidity is bad, too little of it can also affect your plants.

Know that the humidity is a bit too low if you notice the following:

Wilting Leaves

Leaves on plants can droop or wilt even though the soil is damp but the air around them is too dry.

The real reason for this is that the plant is losing more water through transpiration than it is able to replace through soil watering.

Brown Leaf Edges

brown leaf edges

Whenever the humidity is on the lower side, the tips and the edges of leaves can dry and turn brown.

Ferns and other tropical plants, which prefer high humidity, are especially prone to this problem.


Learning how to decrease humidity in terrarium is all about understanding what could throw the balance off in the first place.

Excessive watering, using incorrect substrates, ignoring the temperature, and not pruning when required can lead to an imbalance in humidity.

So, use a hygrometer to keep a close eye on the humidity levels and then take steps accordingly.