How to Make a Closed Terrarium (Hands-on DIY Guide)

Who doesn’t love a vibrant, closed terrarium?

Your very own (self-watering) miniature jungle, full of lush green tropical plants and mosses.

A sealed ecosystem that, while beautiful, is also quite the balancing act. Getting the right plants, materials, and containers is the first step to a functional closed system, but they also have their nuanced care.

So, if you want your slice of nature to be as healthy as it is gorgeous – you’ve picked the right guide.

From picking the best plants to design tips to make your project pop! Read on to learn how to build your self-sustaining closed terrarium.

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A closed terrarium is essentially a miniature enclosed ecosystem in glass.

One that’s able to support itself with minimal effort or intervention by recreating many of the world’s natural cycles.

That includes its very own miniature rain cycle and, in the case of bioactive terrariums, a nutrient cycle, too.

As water evaporates from the plants and surfaces, it condenses on the glass and then drips back down into the soil – thus, watering itself! (Here’s an in-depth look at how terrariums work).

So naturally, when considering how to make a terrarium, we need to keep these principles in mind. The idea is to build a system that can look after itself so we don’t have to.

Of course, being a closed terrarium means you need to be able to seal it, but it doesn’t always need to be completely airtight.

Loose seals can still work well as long as they can trap moisture and humidity (besides, it can be a good practice to open a closed terrarium now and again to get some fresh air exchange).

Don’t worry if you already have the perfect glassware picked out and it’s lidless (as they often are, sigh); we still have options. After all, even containers with large openings like fish tanks/fish bowls can make stunning terrariums.

Naturally, effectively recreating an ecosystem in glass takes an intentional process.

That’s why I often like to say that building a closed terrarium is a lot like building a house.

You’ll need a good foundation, lots of structure and support, and plenty of drainage (and, of course, a boatload of gorgeous plants). Each is assembled in appropriate terrarium layers.

Here’s how that looks:

1 | The Drainage Layer – A foundational structure and reservoir for excess water to drain into. Sometimes, it includes an activated charcoal layer and mesh barrier.

2 | The Substrate Layer – The physical and nutritional support for your plants. For vibrant, healthy plants, you’ll want to choose a high-quality tropical substrate mix over a standard potting soil.

👉 Our Signature Terrarium Substrate Mix is made specifically for this.

3 | The Hardscape – All the cool rocks and branches that mimic the mountainous contours of the natural world. They bring scale and dynamic shape to closed terrariums.

4 | The Closed Terrarium Plants – Choose appropriate plants from the various categories of tropical species and create your vibrant miniature landscape!

5 | Personal Touches – Once the ecosystem is in place, it’s time to create your final scene and add any last highlights. Natural or otherwise (dinosaur figurines count as natural, right?)

Finally, add a lid! (It’s not really a layer, but it’s essential nonetheless).

Closed terrarium plants come in many shapes, sizes, and growth habits.

After all, pretty much any tropical plant can thrive in a tropical terrarium. It’s finding smaller terrarium plants that’ll fit in the container, have the same light requirements (and look good together) – that’s the real challenge.

I like to categorize them into the following: ferns, vines, foliage, moss, and epiphytes.

What closed terrarium plants you have available will differ in different countries, but you’ll generally want a mix of all of these types of plants to get a natural-looking scene.

Just don’t choose plants native to arid climates like cacti and succulents… they’re never going to last in the humid conditions of a closed terrarium. Opt for an open terrarium instead. Then, there are air plants that can work in a closed terrarium, but you’ll need to give them additional airflow.

My guide to closed terrarium plants lays out the best of each category and gives you plenty of options to explore.

In terms of the actual planting, I like to start with the tallest plant as it’ll dictate the layout of the land. Then, use the smallest plants as decorative highlights.

👉 Ready to go? Check out our Terrarium Moss Collection on the store!

A harmonious closed terrarium ecosystem has a variety of moving parts.

The first being plants that’ll thrive in the moist environment and humid air (so we’ve got that covered). Now we’re onto the more nuanced things to consider.

For truly maintenance-free growth, choose small plants that stay small. Lots of those tiny plants at the store are actually just baby plants that’ll get much bigger!

Terrarium lighting is another big one to consider. You’ll need to provide consistent, even light that satisfies the needs of your tropical understory plants but doesn’t burn them. They’re typically quite delicate, after all.

For a natural light source, you’ll want your terrarium to be in a bright spot that’s out of direct sunlight.

Though it can be much easier to use a grow light setup. That way, you can guarantee that all the plants are getting enough light, and there’s no risk of scorching. It needn’t be anything fancy; a simple grow bulb in an Ikea light will do (yes, that’s speaking from experience).

Finally, creating a bioactive terrarium is the ultimate step in a self-sustaining closed terrarium. Enlisting the help of beneficial terrarium bugs completes that final all-important nutrient cycle.

So your ecosystem can effectively process any plants that have checked out of life and use them to create nutrients for those still left in the game.

If you prefer to go the whole DIY route – as I do – then you’re going to need to source your own supplies.

Thankfully, many of these can be sourced easily online (be sure to check out our terrarium supplies for sale), from local stores, or even fashioned yourself in the case of tools.

• Drainage materials – LECA clay balls or lava rock are my top picks because they’re lightweight and porous.
• Substrate – A suitable tropical blend with plenty of drainage and water retention. As a rule of thumb, you’ll typically need enough to create a layer about 4 inches deep.

• Clear glass container – Pretty much any closed container of uniform shape and reasonable size can work, from apothecary jars to spice jars, whisky bottles, and candles. Bigger isn’t necessarily better, but it’s certainly easier to work with.
• Tools – Not all tools are essential terrarium tools, but some are highly recommended, e.g., long tweezers really help to position plants, and long scissors are needed to trim them.
• Springtails – We recommend a culture of springtails for every closed terrarium project. These super tiny, mold-fighting bugs are the single most effective way to keep your terrarium clean and healthy.

• Plants – You’ll need multiple plants to create a natural-looking tropical scene. Look for dwarf species or slow-growing plants.
• Lid – If your glassware doesn’t come with a lid, then find yourself one! (This shop on Etsy provides custom-sized acrylic lids).

Thankfully, there are quite a few terrarium lid options out there.

When it comes to getting lids for open containers, I find getting acrylic disks cut to size is the best option. There are plenty of companies online that can cut something to a precise dimension for a reasonable cost.

Or cling film (Saran wrap) works in a pinch! You can snip the loose edges and get a clean finish if you’re careful. However, it does tend to get quite dusty.

As we’ve touched on earlier, bright indirect light is the name of the game in closed terrarium care. Plenty of energy and none of the risk of scorching.

When it comes to watering, you can use the old-fashioned method of adding water when the soil feels dry, but honestly, that’s a bit of a fuss in the confined space of a terrarium.

I find the better way is to judge the amount of moisture in the system through the amount of condensation of the glass. A light fog on the glass throughout the hottest part of the day is completely normal and healthy.

If you see no fogging of the glass at all and/or the substrate is looking bone dry – it’s time to add some water. Just a little at a time, as it’s easy to add and difficult to remove.

See my guide on how to water a terrarium for the full technique.

Finally, for healthy plant growth (but not too much growth), I prefer to add organic matter to my substrate in the form of earthworm castings. Failing that, a diluted organic water-soluble fertilizer can be sprayed periodically.

You can even add a chamomile tea bag to your mix for a bit of natural diluted fungicide.

There you have it: everything you need to know to build a closed terrarium.

You could start by following our step-by-step How to Make a Terrarium guide if you like or go it alone with your newfound skills.

Check out our list of Best Terrarium Plants or our Ultimate Guide to Terrarium Plants if you need more plant inspiration.

Now go forth, and build (and show me what you produce)!