Terrariums have become very complicated.
All you need is a container and some plants. You can even just use the soil they came with.
My terrariums have run for YEARS with no drainage layer or membrane, no charcoal. Always lidded, never sealed.
That’s really all you need to know, but I wrote a thing, so KEEP READING.
Overwaterers, this is not for you. Terrariums need watering quarterly, with a spray bottle.
What do you need to make a terrarium?
A container
Keep an eye for glass containers in thrift stores because you can get some awesome terrariums. Good garden centres also have options, albeit pricy ones.
Scour Facebook for damaged aquariums (watch out for sharp edges!)
There are also some cute options on Amazon.
Plants
Just go anything that will fit at the time.
Terrariums are an AWESOME way to grow plants quickly, but the downside is that they will need pruning.
What soil do you need for a terrarium?
Use the soil the plant came in.
Seriously.
I’ve made my last few terrariums from the soil that came with my plants. I did need to add some extra to the big one, but I just used whatever I had hanging around.
Even a pretty dense soil can work. Just water it well before you use it and be careful when you’re topping up.
A caveat: Check for pests first. You don’t want to import pests into your terrarium.
Bugs
Totally optional but springtails and isopods will eat decaying matter and they look CUTE.
Things you’ll see recommended that I don’t use
I have used all these things in the past because I thought they were required.
I can confirm that they are not:
- A base layer of gravel or LECA
- Some sort of membrane beneath the soil
- Charcoal or any fancy substrate
- Moss (though, like the springtails, it is does make for an aesthetic terrarium)
How to make a terrarium in a jar, step by step
It might be easier to just watch me make one in this video:
If you would prefer me to tell you to build one, the instructions are as follows:
- Buy a terrarium and some plants
- Leave plants to dry out a bit – too dry and it becomes a dusty mess, too wet and it becomes a muddy mess.
- Remove some of the soil from the plants
- Arrange the plants in the terrarium until it’s pretty
- Backfill the gaps in the soil later using the soil you removed in step 3.
- Firmly tap the terrarium on a solid surface to remove any air pockets (firm but gentle – glass breaks!)
- Spend 10 minutes trying to wipe soil off the inside of the glass, then give up (don’t worry, it’ll be easier to clean after a couple of days.
- Fin.
Here’s one I made earlier:
Do you need a drainage layer or charcoal in a terrarium?
No.
The drainage layer doesn’t really do anything (and as there are no holes in the bottom of your terrarium any excess water ain’t going anywhere anyway).
I have had terrariums with multiple layers and ones that are just soil. They both worked like a dream. Drainage layers aren’t detrimental, they’re just not necessary.
I would highly, highly recommend using a spray bottle to water rather than something like a watering can. Terrariums need watering very rarely and it’s more of a moisten than a full on water.
Open, closed or sealed: which should you make?
Definitely a closed terrarium.
Forget about sealed terrariums.
Terrariums grow FAST and you need to be able to get in and prune pretty often.
Open terrariums are cute to look at, but since they don’t really have the benefits of a closed terrarium, you’ve basically just got yourself a pot with no drainage holes, which is a disaster waiting to happen.
The benefits of a closed terrarium:
- You don’t need to water them often– it may take you a couple of weeks to get the moisture level right, but other than that you will rarely need to water. I’m talking three times a year.
- They retain humidity – it’s not just that the humidity is pretty high, it’s also consistent, which tropical plants love.
- The glass retains warmth – tropical plants also love to stay warm, and whilst an unheated terrarium will fluctuate a bit temperature-wise, glass warms up pretty quickly when the sun shines on it, even in winter.
Put those three factors together and you have as close to the ideal environment as a houseplant could hope for.
Which plants should you put in a terrarium?
These are the plants I’ve had great success with in terrariums:
- Begonia – they grow like weeds in terrarium, yet in the real world I struggle to have them retain more than one leaf at a time.
- Fittonia – a terrarium classic BUT I would recommend pruning often because they get pretty leggy.
- Air plants – they look cool and are basically zero effort – no substrate needed. HOWEVER it may be a lil damp in a smaller terrarium so proceed with caution.
- Those tiny Phalaenopsis orchids – also no substrate needed.
- Syngonium – I struggled with my Neon Robusta until the terrarium and she’s thriving now
- Small ferns – my button fern loves the terrarium. Weirdly maidenhair ferns do NOT tend to do well in terrariums. My theory that they thrive on attention remains intact.
Contrary to popular belief, there are very few plants that will naturally stay small. The vast majority of houseplants will grow like the clappers when you drop them into a warm, damp environment.
How do you look after a terrarium?
That’s the neat part, you don’t!
The trickiest part is getting the moisture level right at the beginning. Too dry and the terrarium won’t work optimally, too wet and you’ll get mould.
I like to water the soil before it goes into the terrarium and then squeeze it to get all the excess moisture out. If you start seeing mould DON’T PANIC. It’s fine, just take the top off for a couple of days and let some of the excess moisture escape.
If you don’t see any condensation on the glass then you need more moisture. Spray the soil with a spray gun, leave overnight and repeat until you start seeing condensation on the glass.
Once you start seeing condensation form on the glass then it’s damp enough. Put your terrarium somewhere bright and…that’s it. If you stop seeing condensation on the glass in a couple of months, spray it again.
You can (and probably should) fertilise your terrarium with plant food. I have not, and nobody seems to mind.
When it comes to pruning, my tried and tested method of simply hacking away at it has never failed me yet. Once terrariums get going they grow fast so any mistakes disappear quickly enough.
How long do terrariums last?
As long as you want them to.
There’s no lifespan on a terrarium. It’s Theseus’ ship: parts get replaced, plants get swapped out, and I recently moved mine into a bigger tank, but it still feels like the same terrarium. You know how people inherit a Hoya or a Christmas cactus from a relative? I reckon you could leave someone a terrarium.
The famous sealed ones do last decades untouched. David Latimer’s was made in 1960, last opened in 1972, and is still going. Cool, but it isn’t the goal. Sealed means you can’t get in to prune, propagate or rehab anything, which is most of what I use mine for.
What actually kills a terrarium
Mould. Almost always too much moisture at the start. Take the lid off for a couple of days and let some escape. A population of springtails will deal with the rest. You don’t need charcoal.
Rot. Start with damp soil rather than wet soil, then spray. The humidity means your plants never need the soaking a potted plant would get. The water just evaporates then condenses right back into the soil.
Overgrowth. Terrariums grow fast, and thick growth traps water and rots leaves. Hack away at it.
Low light. The glass is another barrier between your plants and the window, so the inside of a terrarium is darker than you might think. Bright spot, or a grow light (or old aquarium light, as the case may be).
Pests. Aphids are the worst offenders, but an enclosed space is the easiest place to spot and deal with them.
Can a terrarium look after itself?
Mostly, yes, and it doesn’t need to be sealed. A big container with small plants cuts the pruning right down, and a clean-up crew of springtails and isopods eats the decaying matter.
Going bigger: making a terrarium in an old aquarium
I appreciate that not everyone has a boyfriend that is always willing to donate an aquarium to a worthy cause but I do (brag) and LOOK:
Look at the fern sending a runner up the right wall. Creepy.
You’ll see that there are a couple of pots of Pothos N-Joy in there. They’re just over-wintering in the terrarium so they can put on a few more leaves before venturing out onto my plant shelves.
The soil is just a mash up of whatever I had and you’ll notice no base layer.
Give that Begonia a month or two and and it will fill the tank. It is a (pretty) MONSTER.
Is it cheaper to make or buy a terrarium?
MAKE
99% of the terrariums sold have entirely the wrong plants. Succulents are an extremely common terrarium plant yet they are totally unsuitable (I have an article on how to keep jade plants in terrariums and it is TRICKY which is sad because the best thing about terrariums is that you can plonk a plant in there and it will grow like a weed with no input from you).
