A closed terrarium is a great option to grow and display plants that like a humid environment, including many tropical and some temperate species. With the right approach, you can make and maintain a closed terrarium that will keep plants growing happily for many years.
What is a Closed Terrarium?
A closed terrarium is a terrarium that is not open to the area around it but is sealed to create a small ecosystem within a lidded glass container of some kind.
Different terraria can look very different from one another. They can take very varied shapes and forms. But all closed terraria share in common the idea that they are sealed, to allow water to circulate within the system.
How Does a Closed Terrarium Work?
A closed terrarium will operate in the same way regardless of its size or shape. The water circulation in a closed terrarium is like a miniature version of the world’s water cycle.
The idea is that water from the plants and the growing medium evaporates. It then condenses onto the glass of the terrarium and drips back down into the growing medium where it can be taken up by the plants once more.
This means in theory that a closed terrarium can be a closed-loop system, requiring minimal to no additional water over time. It can therefore, when designed and managed correctly, require much less time and effort from us over time.
Closed terraria can also have closed-loop nutrient cycles. If you create a bioactive terrarium with creatures to ‘recycle’ waste within the system, then like water, nutrients will cycle through the system and theoretically, no inputs will be required and the system should thrive with minimal intervention long-term.
What You Need To Make a Closed Terrarium
A closed terrarium is relatively easy to make and especially if you select reclaimed items and materials, it can be relatively affordable to do so. If you use a reclaimed or upcycled container then you need not spend a fortune to get a beautiful display.
As a minimum, all you need is:
- A clear glass container of some kind with a lid/ seal.
- Terrarium soil/ substrate.
- Suitable closed terrarium plants. (Plants that like the humid conditions a terrarium of this kind can provide.)
Optional Additions for a Closed Terrarium
Once you have the basics in place, you can have some fun thinking about how you might improve a closed terrarium with additional features.
You might consider adding:
- Detritivore terrarium ‘bugs’ for a bioactive terrarium system.
- Natural features such as wood, rocks, etc…
- Other fun, quirky features to personalize your terrarium display.
If you have a suitable substrate or growing medium, and add terrarium bugs, you can create a bioactive terrarium – one of the most sustainable types of closed terrarium that you can have.
How to Make a Closed Terrarium
To make a closed terrarium:
- Select your container and make sure it has a lid that fits snugly.
- Decide which plants you wish to grow within your closed terrarium and source these plants.
- Create or purchase your substrate/ growing medium to suit the plants you will grow. Add this growing medium to your closed terrarium.
- If you have chosen to add additions to create a bioactive terrarium, or have other additions you wish to include, add these now.
- Place the plants into your new closed terrarium. Introduce terrarium detritivores if you wish.
A good closed terrarium combines practical considerations with aesthetics to create a functional and pleasing mini ecosystem and display.
Maintaining a Closed Terrarium
Creating a closed terrarium is only the beginning. You also need to know how to maintain a closed terrarium over time. The basic things you need to think about are:
- Placement. (Thinking about Light and Temperatures)
- Ventilation. (Opening a closed terrarium now and then.)
- Monitoring the Water System.
- Monitoring Plants (Pruning as Necessary).
- Cleaning the Glass of a Closed Terrarium.
For a closed terrarium to function as it should, it is important to place it in a location where it has the lighting and the temperatures that it requires.
In most cases, a closed terrarium will do best where it will not get too warm, and where it is in bright but indirect light, or even lower light conditions and not in direct light.
Most of the time, a closed terrarium will, as the name suggests, be kept closed, so that independent air and water cycles develop within it.
But plants don’t always create the perfect balance between carbon dioxide and oxygen within a closed terrarium and so it is a good idea to open the terrarium for a few hours every couple of weeks or so to refresh the system and provide some additional ventilation.
Likewise, a closed terrarium has its own independent water cycle, and in theory, the water should cycle so you do not have to replenish it frequently. You will likely still need to add water to a closed terrarium, however, now and then.
Understanding how much water you need to add, to keep things moist but not cause waterlogged conditions, is key. Remember, this will depend both on the plants you are growing, and on the environmental conditions. You will usually need to water more in summer, and much more sparingly over the winter months.
Keep an eye on your plants within your closed terrarium. They will usually tell you if they need water, or if something else is wrong. You will be able to tell by how they look.
Another important maintenance task when you have a closed terrarium can also be to prune those plants that need it. Some plants should be pruned regularly to keep their size in check and to prevent them from contacting the sides of the container.
It is important to keep the glass of your closed terrarium clean so that the efficiency of photosynthesis of the plants within is not reduced. Cleaning will also keep a closed terrarium looking good.
Simply take a rag, brush, or other tool and clean any build-up on the glass. Make sure you don’t harm plants by using chemical cleaning products. Natural cleaning products will clean the glass on your closed terrarium just fine.