People have a lot of questions around terrariums.
Which to be fair, is to be expected around such a diverse and interesting hobby.
In this article, I’ve rounded up the most common terrarium questions being asked on the internet. So you can get your query answered right away (and hopefully preemptively answer your next one!).
Let’s dive in.
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- 1 | Are Terrariums Easy to Care For?
- 2 | Are Terrariums Self-Sustaining?
- 3 | Are Terrariums Sealed? / Can Terrariums Be Airtight?
- 4 | How Do Terrariums Get Carbon Dioxide?
- 5 | Who Invented Terrariums? / Where Did Terrariums Come From?
- 6 | Are Terrariums Popular? / When Were Terrariums Popular?
- 7 | Can Terrariums Be Open? / Are Terrariums Good for Succulents?
- 8 | How Often to Water Open Terrarium?
- 9 | What Do Terrariums Need to Survive?
- 10 | Where to Keep Terrariums?
- 11 | What Are Terrariums Used For?
- 12 | Terrarium or Terranium?
- 13 | Can Terrariums Be Outside?
- 14 | Terrarium vs Greenhouse?
- 15 | What Are Terrariums Made Of? / Can Terrariums Be Plastic?
- 16 | Can Terrariums Hold Water? / Can Terrariums Be Used as Aquariums?
- 17 | Can a Terrarium Be Too Big?
- 18 | When to Repot Terrariums?
- 19 | Are Terrariums Good for the Environment?
- 20 | Why Are Terrariums Important?
- 21 | Where to Get Terrariums?
- Over to You
1 | Are Terrariums Easy to Care For?
Terrariums can be incredibly easy to care for.
Honestly, it’s all about getting the balance right.
If you build your terrarium with the best practices and care for it appropriately, you can create a miniature ecosystem that largely looks after itself.
Some of my terrariums only need watering once every few months.
On the other hand, get the balance wrong and it can take some challenging interventions to fix. It’s always better to underwater than overwater!
> See our Terrarium Care Guide for more care advice.
2 | Are Terrariums Self-Sustaining?
To be truly self-sustaining, a terrarium has to meet a few extra conditions than your basic planted glass container.
Creating one of these is called a “bioactive terrarium.”
Every closed terrarium is able to form its own little water cycle, but a self-sustaining terrarium needs a decomposition cycle too.
In order to stay fresh and healthy, and have nutrients recycled for the plants, you’ll need a healthy microflora (helpful bacteria and fungi) and microfauna team (helpful critters commonly referred to as a “clean-up crew”).
> See our guide to Building a Self-Sustaining Terrarium for more help.
3 | Are Terrariums Sealed? / Can Terrariums Be Airtight?
A terrarium in the truest sense is usually sealed.
The seal helps to trap humidity, and to create the all important tropical conditions inside the terrarium container.
That being said, a completely airtight seal is not required.
Containers with narrow openings (like bottles or carboys) still trap a reasonable amount of humidity, even without a lid. Or, larger tank style terrariums often employ a lid with a partial opening, to allow a consistent level of airflow.
As long as you’re creating enough humidity for your plants, the only other issue with a partial seal is that you’ll have to water more often.
4 | How Do Terrariums Get Carbon Dioxide?
Most terrariums will get enough carbon dioxide gas exchange from being periodically opened.
It’s always a good idea to get a little airflow into closed terrariums, even just for a minute or two.
Though, a bioactive terrarium could also (in theory) provide enough carbon dioxide through the respiration of the microfauna and microflora inside.
5 | Who Invented Terrariums? / Where Did Terrariums Come From?
As with all good things in science, terrariums were invented by accident.
Back in Victorian times, the story goes that botanist Nathaniel Bagshaw Ward left an insect observation jar unattended, and when he returned a fern spore had germinated.
It doesn’t sound all that amazing now, right?
But to his credit, he immediately recognized the benefits of having a container that could grow tropical plants (which were all the rage back then).
The terrarium was first named a “wardian case” after its creator, and ended up being very popular indeed.
6 | Are Terrariums Popular? / When Were Terrariums Popular?
Terrariums are incredibly popular right now.
Partly because we’ve all had a lot of time at home recently… but also because the houseplant boom is in full swing too.
The terrarium industry on a whole is really starting to mature, and I can only see it getting better and more popular as time goes on.
Besides now, there has been a few moments in history when terrariums have been especially popular.
Probably none more so than when the terrarium was first invented. Back then, the Victorians were “fern crazy,” and terrariums were one of the few ways to transport and keep ferns alive.
So, the wardian case became somewhat of a staple in the home.
I can’t blame them, I love a good fern.
7 | Can Terrariums Be Open? / Are Terrariums Good for Succulents?
A classic tropical terrarium is closed in nature, but modern open terrariums do exist.
With the recent surge of succulents and cacti (thanks Pinterest) open terrariums have cemented a place for themselves in popular culture.
Succulents will quickly suffer in wet, humid conditions – so you’ll need an open container which cannot trap humidity and gets plenty of airflow.
As a rule of thumb, tropical plants need a closed terrarium, and arid plants need an open terrarium.
> Check out my guide to Open Terrariums.
8 | How Often to Water Open Terrarium?
Open terrariums are essentially just elaborate glass plant pots.
No shade, just being real here.
As they don’t trap humidity or recycle water, the general watering needs of the plants will dictate how often you need to water the terrarium.
For succulents and cacti, this is usually pretty infrequently. Though in a terrarium you do need to me more mindful of drainage (or lack thereof).
> Check out my guide to Watering Terrariums.
9 | What Do Terrariums Need to Survive?
Like all plants, terrariums primarily need light and water to survive.
For tropical terrariums, bright indirect light is the gold standard. That way the plants are able to receive as much light energy as possible, without the risk of burning.
Consistent moisture is a given, especially for the more tropical varieties.
To grow strong and healthy, they’ll also need a variety of minerals and organic materials. I prefer to use earthworm castings as organic compost in my mix to fulfill these requirements.
10 | Where to Keep Terrariums?
The perfect place in the home to keep terrariums is somewhere warm and bright (but not in direct sunlight).
If you’re in the Northern hemisphere, a North-facing windowsill is ideal.
An East-facing would be the next best. It’ll receive a little direct sunlight in the morning but the Sun should be at its weakest.
If you have a West or South-facing window, you’re better off either shielding the window with a screen or moving the terrarium several feet away from the light source.
> Need more help? See my guide to Terrarium Lighting.
11 | What Are Terrariums Used For?
Terrariums are used for a variety of practical and artistic reasons.
I think everyone can appreciate a slice of nature in the home, and having one because they look nice and make you feel good is the number one reason to own one.
But, they’re also great for rare tropical plants as a terrarium is an easily controllable environment that can shield a plant from cold and dry air.
They’re also good for transporting plants for the same reason (though nobody realistically does it).
Finally, they’re also used in scientific study (though we’re crossing into the terrarium vs vivarium definition here).
12 | Terrarium or Terranium?
To my knowledge, there’s no such thing as a “terranium” I’m afraid.
Though it’s by far the most commonly used mispronunciation. Maybe something to do with the way the word “terranean” (meaning of the earth) is spelled/said.
I don’t think anyone gets it right first time so I wouldn’t worry!
13 | Can Terrariums Be Outside?
Keeping terrariums outside isn’t really feasible in most cases.
In truth, it’s kind of besides the point – but there are practical challenges too.
As the terrarium would be exposed to natural environment, you’d need to live in a tropical climate that can keep it consistently warm. You’d also likely have to protect it from the Sun under a tree or cover.
In the UK with this cold and miserable climate? It ain’t happening.
14 | Terrarium vs Greenhouse?
Following on from the concept of outside terrariums, greenhouses are arguably a form of terrarium.
Contrary to popular belief, greenhouses aren’t exclusively outdoor things, and indoor greenhouses are a legitimate alternative in some cases.
There are some subtle differences though:
- Terrariums look to create an ecosystem, whereas greenhouses are a simple way to create certain conditions.
- Filling a greenhouse is a lot more free and easy. Terrariums require a particular way of making them and planting them up.
- Greenhouses are mostly functional and terrariums are mostly artistic.
15 | What Are Terrariums Made Of? / Can Terrariums Be Plastic?
Glass is generally favored for its cleaner aesthetic and sustainability, but plastic is the much cheaper (and much lighter option).
As long as it’s fully transparent and can let light through, a plastic container is absolutely fine.
In fact, it can be a great way to up-cycle plastic bottles and boxes!
16 | Can Terrariums Hold Water? / Can Terrariums Be Used as Aquariums?
Though it’s common to use old aquarium tanks as terrariums, it rarely works the other way around.
Some terrarium containers can hold water, but many won’t.
Not for containers with panels.
Anything that’s built for that purpose and adapted (e.g. a fish tank) or is just one piece of glass (e.g. a bottle) is of course going to be fine. But, I’d never assume a purpose-built terrarium with multiple parts is able to hold water.
Most like the seals are not able to take the water pressure for long, if at all.
If you want to waterproof a particular container, you can often use silicon on the seals.
17 | Can a Terrarium Be Too Big?
A terrarium can never be too big!
I suppose you could run into some practical challenges as you get into huge installations, but there’s nothing fundamentally restrictive about bigger terrariums.
Take a look at the Jewel Changi Airport in Singapore and you’ll see what kind of scale it can be done at!
18 | When to Repot Terrariums?
The general idea of terrariums is to not need re-potting.
Ideally, we’d have a selection of plants that can grow to fit the space. However, it’s not uncommon to put plants in there that will last a while.
If a plant will take years to reach a point where it’s too big, that seems reasonable to me.
At that point you can simply remove the big boy plant and replace it with something else.
In reality, most terrariums are going to need some degree of maintenance on a regular basis. Vines often need snipping back or foliage plants can be encouraged to grow denser with some strategic pruning.
19 | Are Terrariums Good for the Environment?
Sure, in some ways terrariums are good for the environment.
As a closed system, they’re able to constantly recycle water. Which is especially nice in regions of the world where water can be scare.
Plus, they tend to trap a bit of heat in the glass, so it’s easier to reach the desired tropical temperatures without the need to heat your house.
On the flip side, as with any hobby we should be mindful of the materials and resources we use.
Take care to source your plants and materials sustainably (sphagnum moss in particular) and avoid non-renewables like peat moss where possible.
20 | Why Are Terrariums Important?
In our current global climate, a huge number of plant species are at risk of being lost.
Though terrariums are in many ways an artistic hobby, they are employed by botanists around the world to preserve and protect a huge number of plants.
At a small scale, they can be used to grow and observe species of note. Or, the likes of Kew Gardens has the largest collection of plants in the world – safely growing millions of species under glass.
21 | Where to Get Terrariums?
There are so many great places to get terrariums these days.
The range of purpose built terrariums is growing by the day, with lots of solid options on Amazon with the likes of geometric terrariums or wardian cases (if you’re feeling historical).
There’s always a fantastic range of artistic glassware on Etsy too.
Alternatively, I love to up-cycle and reuse where possible. Old preserves jars? Yes. Fish bowls? Sure. Empty wine bottles? Too many…
> See my guide to Terrarium Containers for more inspiration.
Over to You
If you’ve made it this far, I salute you and your new found terrarium knowledge.
Hopefully you find some useful terrarium tips along the way.
Be honest, did you pronounce it [ter-ray-nee-um] too?
Let me know in the comments.