7 Plants you shouldn’t put in terrariums

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Let me just preface this by saying you can grow ANY plant in a terrarium. ANY PLANT. But to grow certain plants you’ll practically need a degree in botany to stop them rotting.

This list is more of ‘plants beginners shouldn’t put in terrariums because they’ll probably rot and ruin the whole thing and make it smell like poo’. But that’s a terrible title.

If you’ve not started your terrarium yet, read this article first.

Succulents

The ‘problem’ with terrariums is that they’re incredibly humid. Ours just…exists at 90% humidity. We don’t have a humidifier or a mister or anything in there.

Succulents will rot in 90% humidity. Anything over 65% is asking for trouble and it’s extremely hard to create a dry environment inside a box that has a damp section (the substrate).

In order to get succulents to thrive in a terrarium, you’d need to create a very bespoke soil mix and probably a scientist to work out how many millilitres of water you need to give it.

It’s just not worth the hassle, when another plant will thrive in there that you can pretty much ignore.

The annoying thing is that plant writers such as myself are battling with seemingly every plant shop in the country recommending succulents for terrariums. My friend wanted to start a terrarium the other week and they sold her a terrarium, soil, and a jade plant. No drainage layer, and a totally inappropriate plant. AAAARGH.

If you’ve already been given your jade plant and put it in your terrarium, and now it’s looking, er, sad af, please take a look at this article, which will tell you what to do.

Pothos

I speak from experience here. I have a pretty medium-sized (123 litres) terrarium, and the pothos has been in there about four months.

It is throwing out about FIFTEEN new leaves, and has attached itself to the back of the terrarium with it’s aerial roots. It doesn’t give a shit about growing through my Calathea Beauty Star, which very kindly grows very compactly (is that a word?). it’s now touching the glass at front with the CREEPIEST roots in the world.

You know how plants grow furry roots in water? Well, 90% humidity is practically water, and the roots are HORRIBLE.

Thanks, I hate it.

This thing will not stop until it’s taken over the world.

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African violets

They just don’t really like it. It’s too damp for them. African violets like higher humidity but they also like to have their substrate dry out a bit, which is difficult to achieve in a terrarium.

Also, I think the easiest way to water is to spray the terrarium down (which goes against everything I believe about misting plants) and an African Violet would HATE that.

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Sanseveria

They’re basically a big succulent, but they grow EXTREMELY fast in the right conditions, so even if you could stop it from rotting, it’d end up making a break for it.

Snake plant roots are incredibly strong too, and whilst I don’t know if they’re strong enough to break glass, I don’t intend to find out.

Realistically, they’d probably rot.

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Hoya (with some amendments)

Hoya could technically grow very well in a terrarium, but you’d probably need to remove all the soil from their roots and give them something to grow up, like a piece of wood.

If you planted the hoya in the substrate, you’d be forever battling root rot, because hoya don’t like to stay wet. They like to dry out a BIT (not a lot, though they will definitely tolerate it) and that’s quite tricky get right in a terrarium.

I personally wouldn’t put hoya in a terrarium, because they probably wouldn’t like to be sprayed. I’d have to put a fogger or something in, aaaand it’s too much. The frog wouldn’t be able to see.

If I got a giant terrarium it is something I’d like to try though.

They’re one of those plants that would probably LOVE being in a terrarium IF you made sure you did it properly. I don’t have the time or inclination to do that tbh. AND IT’S FINE TO ADMIT THAT.

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Air plants

Sure, they like a bit of humidity, but it’s just too much in a terrarium. If you JUST had air plants, and managed to keep the humidity super low, you could probably manage it, but you’d need to do the appropriate research. I just don’t see the point when an air plant would probably prefer to be somewhere with a bit more airflow.

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Ponytail palm

I kind of see why people are putting baby ponytail in terrariums. They look both really cool and really cute, which is a pretty hard combo to pull off.

Even aside from the fact that these things will grow into literal trees *cough* in about 100 years*cough*, they’ve literally evolved to deal with not getting much water.

They have a big thing (technically called a caudex, but I feel like ‘big thing’ describes it perfectly) that stores water. If it stores too much water, it rots.

Ponytail palms and terrariums and not compatible (again, with the caveat that if you can keep humidity down, great, but it’s a pain to do that).

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In the final section of this article, I like to give a little shout out to maidenhair ferns.

TECHNICALLY they love being in terrariums. I had two in mine and they both grew like weeds, which is the exact opposite of what they normally do (which is take one look around my house and instantly drop down dead).

But there are two issues with them, one which could be solved but i don’t want to, and one which is just, apparently something that comes with the territory.

The first thing is that they don’t like to be sprayed. They’ll tolerate it for a bit, but over time the fronds will start to go brown and die. I can tell it’s the spray because the leaves don’t shrivel before they die – they just brown.

You could just spray the substrate, but it’s a pain, compared to just spraying the whole thing – which is definitely something to consider when you’re spraying twice a day (which we’ve found is the best way to add moisture to the substrate without saturating it).

The other issue is that they INSIST on getting aphids. I don’t know how they do it, but they always seems to. As you might have guessed, getting rid of aphids in a terrarium is NOT easy, especially when it’s bioactive (i.e. has bugs in it) and you can’t use pesticides. We have a frog that eats flies for a living, but even he was overfaced by that many aphids.

Maidenhair ferns look pretty, but we decided to swap it for Calathea, which thrive (no something you often hear about Calathea!) in there.

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Take all this advice with a pinch of salt. If you want to try to grow a plant in a terrarium, go for it. This is more a list of plants that don’t grow in a simple terrarium; intended for beginners. If you have special set up to grow ponytail palms in a terrarium ,leave the details below.

Seriously, I think the whole desert terrarium looks so good, but they don’t last long. If you want to grow something like that, make your aquarium open-topped and add drainage holes. Sure, it’s technically now a giant plant pot, but at least your plants won’t die as quickly.

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