How to Make a Closed Terrarium

Last Updated on October 31, 2021 by Phil

Want to learn how to make a closed terrarium? This tutorial will show you everything you need to know from start to finish.

Terrariums are a great way to keep plants indoors. They let you grow plants without the difficulty of dealing with cold weather and adjusting the humidity in your home. This makes them more convenient than houseplants for many people.

Plus, you can easily move the terrarium around. Or start new miniature gardens whenever you feel like it.

Table of Contents

What Do You Need to Make A Closed Terrarium?

One of the best things about making a close terrarium is that you don’t need a lot of equipment. And, the finished product is fairly small so you don’t need a ton of space at home either.

Here are the basic components to get started on your own closed terrarium. Of course, as you gain more experience, you can add more item or create different kinds of closed terrarium.

A Glass Jar
Potting Soil
Plants
Pebbles, small stones, gravel and activated charcoal
Decorations
Work Tools/Mini Garden Tools

How to Make a Closed Terrarium (DIY Step by Step Instructions)

Below, I’ll be going through the steps on how to make a closed terrarium. This DIY tutorial will show you the different things you need along with tips and what to look out for when creating your own closed terrarium at home.

Container

The first thing you’ll need to do is select a container for your terrarium. This will act as the foundation so do take your time to decide the size, shape, look and heft.

I like to use glass jars because they are strong and robust, albeit they’ll be heavier especially once you have the soil and gravel in. Also, transparent glass allows light to easily pass through. This gives it a huge advantage over color glass.

I have fat hands and fingers. So, I prefer jars with big mouths or openings to make it easier to move things around or add decorations later. However, this also means a larger cover.

Depending on what style you want, you can go get a new jar. But, I highly recommend looking for old jars which work great. You can use old fish tanks, fish bowls, cookie jars and candy jars. You can likewise pick something up in a garage sale or flea market to save on cash.

If you happen to find lovely glass jars with etchings or designs, all the better!

Remember, whichever you choose it really up to you and your preference. The only tip I have is that you want something that:

Is big enough to fit the plants you want
Is small enough to sit wherever you want to put it when you’re done
Has enough access to make it easy to tend to the plants as well as add or remove them if needed

Always Keep Everything Clean

Before you begin, one thing to keep in mind is cleanliness.

Here, you not only want to keep everything clean but also sanitized. That’s because you’re going to leave the plants in a closed, humid space. This makes it prone to pathogens, diseases and other problems.

As such, each step of the way, you want to make sure you’re not introducing any potential issues.

The easiest way is to wear gloves. Although, regular washing of hands as you build your terrarium will also work.

Before adding anything to your terrarium, clean it first. This includes the glass.

Potting Soil

To survive, your plants will need potting soil.

Here, go with a soilless potting mix. This ensures that there are no pathogens since soilless mixes are sterilized before they are packaged.

This is something you can be sure of with garden soil. Additionally, you want to avoid garden soil which will compact over time and is likewise too heavy.

Since you don’t want the plants to grow quickly or get big, pick a soilless potting mix with low fertility.

It is a good idea to add activated charcoal with the soil. You can mix them in a container before placing them into the terrarium jar.

Adding charcoal not only adds some organic matter but just as importantly absorbs odors and chemicals.

Some terrarium growers will also recommend adding small rocks and pebbles at the bottom in order to improve drainage. You can do this, although I’ve found that it is not necessary.

That said, an assortment of rocks, pebbles and other small stones are great for design.

Finally, when adding soil, make sure to get it to at least the height of the largest root ball amongst your plants.

Then add water until it is damp. Be careful not to get the water too wet.

Best Plants for Closed Terrariums

The best plants for closed terrariums are small, slow growing plants. In many cases, go with dwarf plants so they don’t take up a lot of space.

Additionally, tropical plants and woodland plants do well since they like humid conditions. You want to avoid cacti and succulents which struggle in closed terrariums. These are better off in open terrariums and dishes.

If you’re looking for greens or foliage plants, moss, ferns and lichen are all great choices.

Since all the plants will live under the same environment, you want to choose plants that have similar preferences including light, watering and fertilizing.

Additionally, where you end up placing it will affect the kinds of plants you get. If you keep it near a window with lots of sunlight, choose sun lowing plants. But, if you decide to have the terrarium on your office desk, lower light plants are a better option.

Sunlight

Your terrarium will need sunlight. But, it won’t be able to tolerate direct sunlight. Otherwise, the plants will get scorches due to the heat.

Instead, keep it near a bright window. Ideally, with exposure to bright, indirect light. You can also use filtered light by covering the window with sheer drapes.

How much light will depend on the plant you choose. But, most cases, they will need a good amount of sunlight.

If you prefer to keep the terrarium in a desk or office with the windows far away, make sure to choose low light plants.

Customized Tools

Due to the size of the opening and the interior of the jar, you won’t be able to use regular gardening tools. As such, small custom tools are best for terrariums.

In most cases, your hands are your best tools because you can bend and change the angle in different directions.

That said I’ve found that different sized spoons work well for “digging”. Similarly tweezers are great for picking up things and moving them around. You can use chopsticks of you feel more adept with them.

Small clippers will take the place of pruning shears.

When it comes to tools, I’ve found that you can use whatever you want depending on the situation. As such, let your creativity run wild. Just make sure to sterilize the tools before using them.

Decorating and Designing a Closed Terrarium

Now that you have everything in, it is time to design your terrarium.

Here’s where you create your own miniature garden inside your jar. And, everything is really up to you.

If you’re starting out or have a small terrarium, then a single specimen is the easiest way to go. This lets you focus on one plant that’s the center of everything. And, you can pick a bigger plant as well that will get all the attention.

On the other hand, multiple plants take a bit more care. You also wan to make sure they’re compatible with one another. But, the benefit here is it gives your terrarium more character and texture.

Avoid overcrowding since more space makes it easier to maintain everything. Plus, if you need to prune or fertilize, it is easier to get into the right position.

Because your jar is made of glass, always check the viewpoint from all directions. This way, one side won’t look unbalanced from the others.

Of course, where you position your terrarium will affect which perspective to focus on. For example, if it is set against a wall or post, then you want to put more focus on the sides that are seen by everyone.

Since there isn’t a lot of space, balance is important. Always remember to balance out the landscape, the plants and non-plant décor.

Cleaning the Terrarium

Once you’ve added all the things you want, it is time to clean the terrarium.

You can use paper towels and a soft brush to remove dirt, soil or leaves from the glass.

This is more about removing all the excess debris.

Watering the Terrarium

Due to its size, watering is the trickiest part of maintaining your terrarium. You want add water a little at a time since once you overdo it, it is very difficult to remove any excess liquid.

In many cases, misting will be sufficient.

That said, the plants need water. And, establishing a rain cycle in your terrarium is the best way to achieve this.

When you water, make sure to allow excess moisture on foliage to dry before you close the lid. If there’s too much water or condensation, take the lid off to allow air in to help excess moisture to dry.

The goal is to have enough condensation such that there looks like a light fog. If it gets any thicker than that or there’s more condensation on the glass, lift the lid for a couple of days or so.

Too much moisture increases the risk of diseases. And, because of the size of the terrarium, it is difficult to thoroughly inspect every foliage. So, you’ll only notice it a little later.

If you do, quickly remove any affected areas and use fungicide if necessary.

When to Take the Lid Off?

In the previous section, I talked about how useful the lid is as it allows you to somewhat control moisture.

And, once you get the hang of how much to water and how to manipulate it if needed, there will be much less maintenance involved.

That said, how tightly the lid fits affects how often you water and allow air in. The tighter the lid is, the more likely you’ll need to allow more air.

Some experts estimate about 15 minutes every 7 days. Removing the lid during this time will allow the carbon dioxide to get in.

Also, do check your plants on a regular basis, if they start to droop or there’s little to no condensation, it is time to water again.

How often you water will depend on a number of factors. These include how tight the lid is, what kind of plants you have, how much sunlight they get and how many plants there are just to name a few.

As such, each terrarium you own will have its own watering schedule. Some need water once every 3 to 4 weeks. Others, only once every 1.5 to 2 months.

In addition to watering, other times you may need to take the lid off is when you prune foliage. You’ll need to remove yellow leaves as well as those that have gotten too long or leggy.

If you notice the latter, it means that the plants are leaning towards the light. As such, it is a good idea to rotate the jar every so often to help them grow in a balanced manner.

Fertilizing the Terrarium

You won’t need to feed your terrarium during the first year. But, after that, your plants will need some nutrients to stay healthy.

Here, the same cycle applies. That is, they’ll need fertilizing during the warmer months but not during winter. So, you can stop feeding once the cold weather arrives.

All they need is a quarter of the recommended strength starting spring and through summer.

Enjoy!

Last but not least, don’t forget to enjoy your terrarium. Part of how to make a closed terrarium is to enjoy the process as well as the end result.

Otherwise, it really isn’t worth the time and effort.

Hope you found this closed terrarium tutorial helpful. Now, it is time to start working on your own.