7 Terrarium Care Commandments for Happy, Healthy Plants

So, how’s your terrarium looking these days?

I know, terrariums are notoriously low maintenance. Alas, that doesn’t give us a free pass for total neglect. They deserve a little love every now and again.

Personally, I’ve seen some terrariums go months with no maintenance and no problems. Which of course, gave me a sense of confidence that these things just work out… But then, I’ve also left another for just a week and discovered a fungal epidemic spread all across the driftwood!

It happens, in fact some problems are fairly common. 

I’ve yet to encounter a terrarium problem that can’t be fixed, but it’s always best to catch these things early. Here’s a bunch of terrarium care tips to keep your terrarium in good shape.

1. Check the Weather: How’s the Humidity?

Everybody knows (but often forget) that houseplants need to be watered regularly. Terrariums are different though, you generally don’t need to intervene very often. 

After all, it’s a closed system. So, they mostly water themselves if conditions are right.

Humidity is your best indicator of whether your plants are getting watered. It’s the result of having lots of water in the system. Enough to saturate the growing medium, and have enough left over to evaporate and saturate the air.

You can monitor humidity through the amount of condensation on the glass.

You can also check for wilting, dry soil, dried-out leaves and a bunch of other indicating factors. 

How much humidity you want in your terrarium is going to depend on what you’re growing in there, but if it’s.constantly fogged up, you’ve overwatered it. But a completely clear terrarium is likely to be dry as a bone. 

Most closed tropical terrariums are going to need 80% humidity or higher. At high humidity levels like this, a terrarium will likely be fogged up somewhat during the hottest parts of the day. If not, it might need a top up.

2. Catch it Early: Remove Dead or Rotting Plants

Plants die, it’s natural. 

Don’t take it personally, but please do act on it.

Terrariums generally don’t have the capacity to deal with it in the same way as a natural environment would. They lack the biodiversity of organisms needed to effectively break down organic materiel.

If left unchecked, any dead plant matter will simply rot. Leaving your terrarium a smelly and unhealthy mess.

That’s why I always recommend removing plants at the first sign of rot… or death. It’ll help to maintain the balance and reduce the chances of a disastrous rot spreading through your plants.

3. See The Light! Then Make Sure it’s Not Too Strong

Sunlight is essential to a terrarium, but let’s not forget that they’re essentially a greenhouse.

Glass containers can – and will – amplify the amount of light they receive. It’s very easy to scorch your plants in direct sunlight.

Just be mindful of where you’re putting your terrariums and what kind of light your plants need.

I’d always be hesitant to put a terrarium directly  in front of a window. Some plants might enjoy that intensity, but most will likely suffer. Though a north-facing window won’t get that direct, bright light.

Personally, I tend to opt for low light plants as they’re far more versatile in where you can put them in the house. If they need a little light boost, you can always add a small grow light. 

4. Let it Rain….Carefully.

On the rare occasions where your terrarium does need a top up, a light shower is always better than a torrential downpour.

You’d be surprised how sensitive some plants can be. Handle them too much (or spray them with a strong jet of water) and you can send them into shock – causing them to shed their leaves.

Watering as evenly as possible is best, so using a spray or mister is always advised. Otherwise you can risk waterlogging some areas, and neglecting others. 

Plus, you can be consistent with your watering too. Five sprays is infinitely easier to replicate than five glugs (?) from a bottle.

5. Let Them Grow (and Intervene When Necessary)

Sure, we all want healthy, happy plants in our terrarium. We should try to create the best conditions possible for them to grow, but terrariums are peculiar things in that we don’t want our plants to grow too well.

Personally, I tend to be very particular about my plant choices. I won’t put anything into a terrarium that has the potential to outgrow it. But even then, that doesn’t give me a free pass on pruning.

Over the course of years, almost all terrariums will need some plant intervention.

Maintaining the balance is important. Though you want some room for plants to grow in and settle in the environment, you still want to preserve the sense of space and scale you created in the beginning.

After all, plants need space to thrive, and we’re mostly restricting them in that sense. They also need light and water, both of which can be altered through excessive plant growth.

Here’s what to look for:

  1. Plants growing against the side of the container. 
  2. Plants becoming so thick and bushy that they begin to block light from reaching others.
  3. Plants growing so tall they reach the top of the container.
  4. Fast-growing plants that are beginning to take over.

You can even prune a plant’s roots to slow its growth.

6. Always be Vigilant. For Mould.

Mould (or mold) is the silent enemy waiting in the shadows of all terrariums.

I can relate to mould, as I thrive in hot and humid environments too. Just like a wave of British tourists flocking to Spain in the summer, mould can quickly take over and ruin a beautiful environment.

That being said, a spot of mould doesn’t immediately spell disaster. After all, it’s part of a natural decomposition cycle. It shouldn’t affect healthy plants.

You can deal with any small patches with a Q-tip and some hydrogen peroxide. Just a quick wipe should do the trick. I also like to spray my terrariums with chamomile tea, as it contains sulphur compounds that can help keep mould at bay.

If any plants are affected (if they have any rot for example) they should be removed, cleaned and quarantined. Or thrown out if they’re a lost cause.

On the flip side, sometimes it’s your hardscape items that get infected, and I’d actually advise just leaving them in and letting the mould run its course. It feeds on sugar and organic materials, and once it runs out, it dies.

I’ve had some driftwood branches get covered in thick mould, and despite a few interventions of boiling and scrubbing, it came back again and again. In the end, I let it go its course and it simply went away after a couple of weeks. 

7. Keep a Clean Home (For Your Plants) 

Nobody likes dirty glass, and neither do your plants. 

Not only does it look awful – and half the fun of terrariums is being able to see them – but it can also restrict the light that the plants receive.

Give the inside of the glass a clean with a lint-free cloth (or you’ll have fibres everywhere) and some warm purified water.

Watering your plants with hard water (high mineral content) is generally fine for your plants, but it can leave a white calcium residue on the glass. Which is why I recommend watering your plants with purified water. Deionised, distilled, carbon filtered – they’ll all do the trick. 

Terrarium Care FAQ

Help, why is my terrarium dying?

Terrariums die for all kinds of reasons, but you’re best off starting with the most common problems and working your way backwards to identify the culprit. Making sure your plants have the right amounts of water and light are a good place to start.

How do you maintain a terrarium?

Learning the basics of terrarium care will go a long way, but applying them to every terrarium will be different. Over time, you’ll come to understand the nuances of each terrarium, and you’ll be able to better identify when things are going wrong.

Do terrariums smell?

Terrariums do have an earthy smell (after all, they are earth) but any hint of an unpleasant odour is an indicator that something nasty is brewing.

Over to You

Do you have any routines or care practices to help us keep our terrariums looking and feeling their best?

Let us know in the comments.

Remember, 1 tip = 1 happy plant.

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Hi! I’m Dan. Welcome to Terrarium Tribe. We’re a collective of people who love to build and care for natural plant terrariums. Join us!

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