Who doesn’t love a vibrant closed terrarium?
Your very own (self-watering) miniature jungle, full of lush green tropical plants and mosses.
An ecosystem that, while beautiful, is also quite the balancing act. Getting the right plants, materials and container is the first step to a functional closed system, but they also have their nuanced care too.
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 find out how to build your very own self-sustaining closed terrarium.
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- How Does a Closed Terrarium Ecosystem Work?
- Key Closed Terrarium Layers (Step-by-Step)
- Choosing the Right Closed Terrarium Plants
- Fundamentals of a Self Sustaining Closed Terrarium
- Closed Terrarium Supplies
- Where to Buy a Closed Terrarium
- Closed Terrarium Care
- Now It’s Your Turn
How Does a Closed Terrarium Ecosystem Work?
A closed terrarium is essentially a miniature ecosystem in glass.
One that’s able to effectively support itself with minimal effort or intervention by recreating many of the world’s natural cycles.
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 (the clue is in the name).
Does that mean a closed terrarium needs to be airtight? Not really. As long as it’s able to trap moisture and humidity, it’ll still function. Besides, it’s often good to air out a closed terrarium now and again to get in some fresh carbon dioxide and get out some mold spores.
As for the sealed container in question, suitable terrarium containers come in all shapes and sizes. From apothecary jars to spice jars, whisky bottles to candles, almost any glass jar/container will do!
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.
Onto the build!
Key Closed Terrarium Layers (Step-by-Step)
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, plenty of drainage, and finally, a boatload of gorgeous plants. Here’s how that looks:
1 | The Drainage Layer – A foundational structure and reservoir for excess water to drain into. Sometimes includes an activated charcoal layer and mesh barrier.
2 | The Substrate Layer – The physical and nutritional support for your plants. For healthy plants, you’ll want to choose a tropical substrate mix over a standard potting soil.
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! (Not really a layer but essential nonetheless).
👉 Within these layers, there are a lot of options and variations. Check out the step-by-step guide to Terrarium Layers to see them all.
Choosing the Right Closed Terrarium Plants
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 small 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 to you 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.
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.
👉 My Definitive Guide to Closed Terrarium Plants lays out the best of each category and gives you plenty of options to explore!
Fundamentals of a Self Sustaining Closed Terrarium
Okay, the first step to a harmonious closed terrarium ecosystem is choosing your 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, going bioactive is the ultimate step in a self-sustaining closed terrarium.
Enlisting the help of beneficial terrarium bugs and microfauna (bacteria and bugs in short) 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. Curious how long closed terrariums can last? Check out this post.
👉 For the full list, check out our 5 Key Elements to a Self Sustaining Terrarium
Closed Terrarium Supplies
If you prefer to go the whole DIY route – as I do – then you’re going to need to source your own terrarium supplies.
Fear not; all of these can be sourced easily online, from local stores, or even fashioned yourself (when it comes to tools).
- Clear glass container – Pretty much any closed container of uniform shape and reasonable size can work. Bigger isn’t necessarily better, but it’s certainly easier to work with.
- Drainage materials (if you opt for it) – Lava rock or leca are my top picks because they’re lightweight and porous, but any gravel will do in practice.
- Substrate – Ideally, a suitable tropical blend or some soilless potting mix with a coco coir base.
- Tools – Not all are essential terrarium tools, but long tweezers help immensely in positioning plants. Then, long scissors are needed to trim them.
- Bioactive bugs – Springtails and isopods are your bioactive bugs of choice. They make a huge difference in fighting mold and keeping your terrarium fresh.
- 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.
👉 See my Terrarium Supplies Guide for a full shopping list!
Where to Buy a Closed Terrarium
Ready-Made Terrariums for Sale
Being a marketplace for creators, Etsy is a great place to find sealed terrariums for sale!
Though, they don’t tend to travel well, so you’re best off finding one within pickup distance. Just do a search within 10-20 miles of your location.
As the next best thing (that does travel well), have you considered buying a closed terrarium kit instead?
A Closed Terrarium Kit
Closed terrarium kits have exploded in popularity recently.
It’s completely okay to live your tropical fantasy when it’s cold outside; that’s all I’m saying.
A typical DIY closed terrarium kit tends to come with everything you need in one package. All the necessary terrarium tools and materials, a suitable container, and a selection of appropriately sized closed terrarium plants.
You could try your hand with a bottle terrarium kit, too (though they’re much harder to work with!).
Closed Terrarium Care
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 through 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 too, for a bit of natural diluted fungicide.
Now It’s Your Turn
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.
Now go forth, and build (and show me what you produce)!