Making a terrarium is a lot like building a house.
They all need a solid foundation, some supporting structures, and finally – a whole bunch of plants.
Though the materials and shapes may differ, the fundamental terrarium building process is the always the same. It’s all about layering from the ground up, and thankfully, I have a blueprint.
So, in this article we’re going to survey the terrarium layer order, step-by-step, so you can make sure you’re on track to a stable and beautiful build.
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5 Key Layers to a Healthy Terrarium
Okay, so I’m using the term “layers” here literally for the first two, but the rest are somewhat figurative.
Making a terrarium is nuanced, and though you may not be adding a uniform “layer” of moss in the same way you would your drainage layer, it’s still helpful to think of it in this way as each step builds on the last.
- The Foundation (false bottom approach or the all in one approach).
- The Substrate (a mix).
- The Hardscape (rocks and driftwood).
- The Softscape (plants and mosses).
- The Final Decorations (finishing touches).
A strong terrarium foundation underpins the whole structure.
It should be tough to resist compaction, and non-uniform to create space for water drainage.
After all, just like the real world, our terrariums need a drainage mechanism built-in. A way to stop water pooling on the surface, which would inevitably cause rot and spell the end of your terrarium.
But not everyone approaches this problem the same way.
The False Bottom Approach
The false bottom approach is one way to artificially reinforce this mechanism.
Essentially, the false bottom is a reservoir created by a layer of large rocks, LECA, pebbles, or other such objects. Here the water can drain from the substrate before evaporating to perpetuate the water cycle – see suitable gravel on Etsy.
The false bottom can be as simple as just the pebble layer, but it’s often kept separate from the substrate via a barrier that’s either natural like sphagnum moss, or artificial like carbon-fiber mesh.
A layer of charcoal is also regularly used to purify the water, though just how much it helps is up for debate.
The All-in-One Approach
As the name suggests, this approach doesn’t separate out the various foundational layers, and instead creates a single mix that serves as the foundation and the substrate.
It’s certainly more difficult to achieve a mix that has the right amount of drainage and support for plants (nutritionally and physically) but it’s arguably more aesthetic, as the overall level of “ground” is going to be much lower.
There are a whole bunch of options when it comes to terrarium soils and substrates.
The one that’s right for you will depend on your choice of plants and build, but if you’re going with tropical plants then good drainage, water retention and aeration as the qualities you want to shoot for.
The size of your plants will mostly determine how thick this layer needs to be. It must be able to accommodate the biggest root ball and still have room either sides for the roots to grow.
Though just remember, you can always slope the substrate to create areas of greater and lesser depth as needed!
If in doubt, the ABG mix is a tried-and-tested tropical substrate, see it on Etsy.
In the art of terrarium building, hardscape is a term for the tough, physical elements that you might add.
Hardscape isn’t used in every build, but it can elevate a terrarium in a variety of ways:
- Helps build a solid base – embedding large physical objects in the substrate can really help to stabilise it, especially if it’s uneven (if you’re making a higher background for example).
- Create a sense of depth – you can physically manipulate the terrarium landscape, using scale and focal points to create a sense of depth. Adding a large object at the front and smaller ones at the back is one way to do this.
- 3D planting opportunities – rocks and branches are able to comfortable grow a variety of plant species on them. This allows for much more creative expression in how you plant your terrariums.
- Pure decoration – if nothing else, hardscape is beautiful unto itself, and can often be a prime feature on its own.
Hardscape elements should generally be added straight after the substrate as they’re often the main feature, but also because their addition can alter the landscape so much.
There’s no point spending hours creating a beautiful green landscape, only to have it warped by a large stone.
Softscape is a term I’ve borrowed from the aquascaping industry (something I do a lot) to describe any of the soft, horticultural elements in a terrarium.
So, we’re talking plants, flowers, mosses – generally anything that’s alive.
You’ll generally want to start planting with your biggest, and most important terrarium plants.
Not just because bigger plants will be harder to place when your terrarium is full, but also because your feature plants should take priority in the best viewing spots.
Once you’ve planted your focal pieces, then you can arrange the rest of your plants to accentuate them.
See the Terrarium Plant Index if you need help picking the best plants.
Mosses typically come last (unless you’ve planted them on wood or rock before adding to the terrarium). This is because they’re primarily there to cover exposed earth for a more natural look, and you don’t know what’s left exposed till the end.
It’s entirely up to you how you decorate your terrarium, and what you use to do it.
Whether you prefer to preserve the pristine plant environment or you want to construct an entire Jurassic Park set with dinosaur figurines (a solid choice) it’s your decision.
Common ways to add decorative layers are by covering the soil with decorative stones, placing figurines amongst the plants or even adding waterfalls features.
*One thing to note is that you’ll definitely want non-reactive decorations. That’s why stones, petrified wood and crystals are a great idea as they won’t degrade or rot away over time.
Now it’s Your Turn
Hopefully you’ve got a good idea of how to layer a terrarium now and what terrarium supplies you may need.
If you’re a terrarium newbie, see our Essential Guide to Tropical Terrariums for advice and tips for every step of process.
Which foundation approach do you tend to favour? Are you a fan of the false bottom method?
Let me know in the comments.