Hermit Garden

Terrarium upkeep and maintenance: how to make your terrarium last

So you’ve put together your terrarium. Now what? The answer is: occasional maintenance. Everyone wants the best for their baby terrarium and to give it the best chance of surviving and thriving. But how exactly are you supposed to go about doing that? What exactly does occasional maintenance mean?

For most terrariums, occasional adjustments of the water levels and maybe wiping down the container walls if they get dirty is all you’ll have to do. It may also be worthwhile to spend some time pruning your plants and removing dying or decaying plant matter. Usually, there are a few signs you can watch out for to decide if your terrarium could use a little maintenance.

In the rest of this post, I’ll cover all the details you need to find out when and why you would need to perform maintenance on your terrarium.

How to maintain your terrarium 

So let’s jump straight into the details. There are two pieces that fit into the maintenance puzzle: what to do and when you should do it.

When it comes to terrariums, there might be a good number of “what to do”s, but most of them should be very infrequent in terms of “when you should do it”. This means that terrarium maintenance overall shouldn’t really take up that much of your time.

Practically speaking, maintenance usually shouldn’t take more than 15 minutes every few weeks at most. Unless you’re doing something like a total renovation of your terrarium.

Here’s a table that lists out all of the common maintenance items you might encounter:

Maintenance ItemWhen to do itHow to do it
Watering the terrarium-You never see condensation in the container
-Substrate feels bone dry
Give a few spurts of water
Airing out the terrarium-Heavy condensation in container visible all day
Substrate feels soggy
-Terrarium hasn't been aired out in many months
Open up the container for a day or two
Wipe off condensation (if needed)
Removing dead plant parts-You see dead plant parts in the terrariumUse tweezers or your hands to pluck out the dead plant parts
Pruning plants-Terrarium looks unkempt
-Plants growing against the container walls
Use scissors to trim down branches that are too long
Cleaning the container-Container is cloudy even when there's no condensationWipe it down with a hand towel or paper towel
Cleaning out mold-Mold is visible in the terrariumSpray down with fungicide, remove contaminated areas, add springtails, or let it resolve itself after adjusting the water levels

Let’s walk through each one of those one by one so you understand how and why you need to do each one of those items.

Adjusting the water levels

The water level is one of the most important things that you’ll need to get right for your terrarium, but it’s also pretty tough to get this right first try. If I had to guess, this is the root cause where most people go wrong when their plants start having some problems.

There’s a fine balance between having so much water that you have a little swamp in a bottle and so little water that your terrarium becomes a desert wasteland.

Ideally, what you’re going to aim for is something in the middle: moist and refreshing, but not soaking wet.

But one thing to factor in is the type of terrarium you have and also the type of plants you are growing. Open terrariums growing arid plants generally will prefer to have less water than closed terrariums growing high humidity loving plants.

There are two ways that you can tell you’ve hit the right spot:

  1. You only see slight condensation in the mornings and evenings inside your container
  2. The substrate feels moist, but not soggy or dry

Here’s how you can tell that things aren’t looking quite right:

  1. The container is constantly fogged up with dense condensation or doesn’t have any condensation at all
  2. The substrate feels soggy or bone dry
  3. You start seeing mold growing in your terrarium
  4. Your plants start to look droopy and have yellow leaves

If you do need to adjust the water levels, here’s what you can do:

Airing out the terrarium

This one’s just for closed terrariums. Open terrariums are already exposed to the air so there’s nothing you need to do about that.

Airing out the terrarium once in a while might be advisable just to make sure that they are getting enough fresh air. Depending on the conditions of your terrarium, it’s possible that there aren’t any organisms in their converting oxygen back to carbon dioxide, leading to a buildup of oxygen and nitrogen which might not be so great for your plants.

There’s not really any way you can tell when you need to do this. Maybe if you see your plants starting to die out, this could be just another root cause to consider. 

In my opinion, you shouldn’t have to worry about this one too much. If you are opening up your terrarium naturally for pruning, water adjustments, or other maintenance tasks, your terrarium is naturally going to get enough fresh air on its own from the opening and closing you’re doing already.

If not, you can open up your terrarium once every couple of months or more if you feel like it. Although, there are many terrarium’s that have never been opened up that are doing just fine. One of my terrariums hasn’t been opened in several months and it’s doing just fine.

Removing dead plant parts

Dead plants are going to come up naturally, even when it’s not your fault and you did everything right. So don’t stress out too much If you have to do this.

When you start seeing full-on brown plants in your terrarium or any brown leaves, I recommend you take those out sooner rather than later.

This is to minimize the spread of whatever disease or rot they might have had. It’s also to keep your terrarium looking green and fresh. No one wants to see brown plants in their terrarium.

If you have a pair, grab some tweezers and lift those guys out of your terrarium. Otherwise, using your bare hands will also work, just be careful not to disturb your other plants too much (not that a little bump is going to kill them or anything). It might require a little bit of digging if they’re firmly rooted into the substrate.

Pruning plants

Pruning plants every so often is advisable, mainly for closed terrariums, but this also applies to open terrarium plants as well.

If you start to see that your plants are growing up against the container walls or just look unkempt in general, it might be time to give them a little haircut.

Preferably, you would want your plants to grow away from the walls so that they aren’t being soaked in the condensation everyday. That could lead to problems like rotting or mold growth. A little bit of pruning is going to control their size while also keeping your terrarium looking fresh.

All you have to do is grab some scissors and start snipping away. Try not to cut off any main branches, just some of the smaller straggler branches that seem to be going awry. You can also cut off any branches that look like they’ve died off.

You can use ordinary paper cutting scissors, but I recommend using scissors specifically designed for pruning plants, like some aquarium scissors. That’s going to make it easier to navigate those tight corners and reach in through the container opening.

You can read more about my recommendation about that here.

Cleaning the glass

Over time, you might start to notice that your terrarium container will start to look cloudy even when there’s no condensation on there. This happens when trace minerals start depositing on your container walls from many cycles of condensation and evaporation.

This could be problematic because it can actually block out some of the lights that would otherwise reach your plants. As you probably know already from your middle school life science class, plants need sunlight to perform photosynthesis. That’s how they convert carbon dioxide and water into sugar and oxygen to feed themselves.

When you reduce the amount of sunlight your plants are getting, you’re effectively reducing the amount of food they’re able to produce. This probably isn’t going to kill them by itself (i.e. plants that can survive in the shade), but it’s just another variable that you probably weren’t factoring in when you built your terrarium to begin with.

It’s also going to mess with the aesthetics of your terrarium. It’s hard to enjoy the beauty of your terrarium when your line of sight is all clouded up by mineral deposits.

Cleaning off the deposit is pretty straightforward. All you have to do is get a microfiber towel, paper towel, or whatever hand towel you have around and just give it a quick wipe down on the inside. 

The only thing I would recommend against is using any cleaning solution while you’re wiping it down. You will want to avoid adding any undesirable chemicals to your terrarium where possible. I wouldn’t want to add any mystery chemicals into my terrarium without having any idea of how that’s going to affect my plants.

Cleaning out mold

Mold is another issue that terrarium builders can run into on occasion. It’s also pretty hard to control since microscopic mold spores are practically everywhere and even spread through the air to reproduce.

Mold in itself doesn’t directly harm your plants, but it can be a sign that your terrarium is over watered. Mold typically only grows when there is an abundance of water.

For the most part, mold should go away on its own if you aren’t over watering your terrarium. No effort required on your end.

But if you want to take things into your own hands or you have yourself a mold crisis, there are some things you can do to eliminate mold from your terrarium:

  1. Air out your terrarium for a day or two
  2. Swap out the mold contaminated parts of your terrarium
  3. Scrape out the mold with a q-tip (can be labor intensive)
  4. Spray down your terrarium with some fungicide
  5. Dip a q-tip in hydrogen peroxide and start dabbing the mold to kill it off
  6. Add some springtails to the terrarium. These guys love eating mold.

How to care for a closed terrarium

First of all, if you don’t know what’s the difference between an opened and closed terrarium, this article explains all of that in detail.

Closed terrariums will be more suitable for high humidity plants that prefer less sunlight. Compared to open terrariums, closed terrariums will require much less maintenance and can tolerate more water.

However, just because closed terrarium plants can handle more water, that doesn’t mean you can give it as much water as you want. Over watering your plants will lead to problems like mold growth and rot. It’s probably the biggest mistake indoor plants gardeners will make with their plants. If anything, your points will handle a little bit of underwatering better than overwatering.

Because all of your plants are in a sealed container, water and air recycles itself like a mini enclosed ecosystem. There’s much less need for you to top it off with water, which is probably the most common maintenance item you’ll have to take care of for a terrarium.

In fact, you have pretty good chances that you won’t have to do any maintenance for your terrarium at all for it to survive. For one of my terrariums, I haven’t done any maintenance on it at all since putting it together half a year ago and it’s still doing fine.

But in general, if you want to maximize your chances of your terrarium surviving or you want to make sure that your plants look fresh all the time, I recommended doing some maintenance once in a while.

After you set up your closed terrarium, you’re pretty much going to do the things I listed out in the first section of this article. But here’s a condensed version of what you’ll want to do to care for it over the long term:

  1. Monitor the condensation levels and soil moisture to check the water levels and adjust appropriately
  2. Open up the terrarium once every few weeks to a few months to let in fresh carbon dioxide
  3. Rotate the terrarium once every few weeks for even plant growth
  4. Prune your plants if they are starting to touch the sides of the container or look like they could use a trim
  5. Remove any dead plants or decaying plant parts
  6. Clean the container if it gets cloudy or dirty

If you want to give your terrarium extra care, you can also throw in some activated carbon and springtails for good measure.

How to care for an open terrarium

Unlike a closed terrarium, an open terrarium is more similar to your traditional indoor house plant and will likely need to be cared for in many of the same ways.

Because of that, open terrariums will require more maintenance than closed terrariums. For the most part, that maintenance will just be watering your terrarium. 

Since open terrariums are not closed systems, water is constantly evaporating and escaping from your terrarium. This means that the water levels will have to be replenished on a consistent basis for your plants. That’s great if you enjoyed the idea of actively caring for your plants more often, but might be a chore if you wanted something that’s more low maintenance.

You also won’t have the condensation on the container as a visual measure of the water levels as with a closed terrarium. Instead, you’ll have to feel the substrate every so often to check the water levels.

Since most plants in an open terrarium prefer dry, arid conditions, they will also be more sensitive to overwatering.

These small nuances means you’re going to have to get good at estimating the appropriate water levels for your plants every time. On the plus side, practice makes perfect. I think once you’ve done it a few times, you’ll start to get into a rhythm of how much water your plants need and how often.

There are also a few other small differences in terms of maintenance items compared to a closed terrarium. Here’s a list of things you’ll have to do to take care of your open terrarium:

  1. Check the soil moisture and water your terrarium appropriately
  2. Rotate your terrarium occasionally for even growth
  3. Prune your plants if they are growing too large for your liking
  4. Remove dying plant parts from the terrarium
  5. Inspect your plants for pests on occasion

Where is the best place to put your terrarium?

The best place to put your terrarium will depend on whether it is an open or closed terrarium.

Open terrariums typically have plants that prefer full sun and can tolerate higher temperatures. This means that they are best placed near a window where they can receive as much light as possible.

Closed terrariums are a different story. When plants are in a sealed container, it’s essentially like growing in a mini greenhouse. This means that when there is exposure to sun, the temperature levels can be much higher than ambient air. This can be deadly to plants (like moss) who cannot tolerate high temperatures.

For a closed terrarium, I recommend placing your terrarium in a room with windows, but not directly on the windowsill. This gives your terrarium indirect lighting, which is what most closed terrarium plants will prefer. These types of plants typically prefer high humidity, low light conditions and often happily grow in the shade out in nature.

One thing I would not recommend doing is placing your terrarium outdoors. There is much less control of the elements of nature like temperature, humidity, and water levels (unless you want to constantly be monitoring the weather report). For open terrariums, this could mean they’re getting a little bit too much water and too much humidity, while for closed terrariums, they might be getting too much sunlight and start baking in the heat.

Keeping your terrarium indoors will ensure that you have more control over the ambient conditions that they’re going to be exposed to. That’s going to give your terrarium the best chances of staying alive.

The one exception I would consider for that rule of thumb is if you are using completely native plants for your terrarium. Even then, I would only consider doing it for open terrariums, where the conditions are similar to how they are in nature. I would still think it’s preferable to keep a terrarium with native plants indoors if possible.

I would also avoid placing your terrarium too close to any heaters or radiators. Anything that raises the temperatures higher than normal is probably not going to be good for your plants.

Why your terrarium might be dying

There’s a number of potential reasons your terrarium might be dying. Often, it’s hard to tell what the exact reason is because usually the symptoms are very similar.

If your plants are looking droopy, turning yellow or brown, or have crispy leaves, those are all signs that your terrarium is not looking so hot.

Here’s a list of potential reasons:

  1. Your terrarium has too much or too little water. If you’ve been watering your terrarium, most likely it’s the former.
  2. Your terrarium is getting too much or too little sunlight. 
  3. Your terrarium is situated near a heater
  4. Your plants have mixed requirements or are not suited for your type of terrarium (i.e. putting succulents in a closed terrarium or mixing succulents with moss).
  5. Your substrate did not have sufficient nutrients
  6. Your plants are infested with pests
  7. Your terrarium was not constructed properly. For more info on that, see this article.

My recommendation if your terrarium isn’t looking so good is to go through the list of potential causes to see if you can narrow down why it might be happening. Once you figure out the cause, it should be pretty straightforward to resolve your issue, but it might involve completely redoing your terrarium if that’s what you have to do.

Why your terrarium is foggy

There are mainly two reasons why you’re terrible could be foggy:

  1. Your terrarium is overwatered. Excessive humidity and moisture will cause heavy condensation inside your container that will fog up the glass 24/7
  2. It’s just mineral deposits on your container that has built up over time
  3. Your terrarium has a slug or a snail inside crawling around when you aren’t looking

If you’ve just built your terrarium or gave it some water recently, there’s a good chance that the fog you’re seeing is just condensation

If you’re only seeing the condensation only at certain times of the day, mainly morning and evening, this shouldn’t be an issue. But if you’re seeing the condensation in your container all day long, your terrarium is probably overwatered. If that’s the case, you should open your terrarium for a few hours and wipe off the excess condensation.

Besides condensation, your terrarium can sometimes get foggy over time after many cycles of condensation and evaporation. The “fog” happens when trace minerals in your terrarium’s water get left behind as any condensed water evaporates.

If you want to verify that the fog you’re seeing is mineral deposits, you can open up your terrarium and rub your finger against the inside of the container. 

If it’s water, you’ll be able to see a clear path with a few droplets of water where you rubbed your finger. If it’s mineral deposits, the path might not be as clear. You might also be able to see mineral buildup along the edges of the path you made with your finger.

You should be able to wipe off mineral deposits with a paper towel or a microfiber cloth. But if it’s a little stubborn, you can try using a little rubbing alcohol to assist. However, I would recommend against using any sort of cleaning solution. That carries additional risk of introducing harmful chemicals into your terrarium that your plants might not tolerate.

The last reason your terrarium container might be cloudy is if there’s a slug or worm crawling on the container walls. This one’s more common when you’re bringing in any native plants or backyard soil to your terrarium. 

It’s possible that some slug or worm eggs could have hitched a ride into your terrarium without you knowing and have spawned full grown slimy habitants crawling around. 

If you see noticeable trails mysteriously appearing in the condensation, a slug or worm might be your culprit.

No need to worry if this is the case. Worms can actually help your terrarium out by aerating the soil. They also provide a bit of diversity and life to your terrarium.

Just wipe off any slime they leave behind and you should be good to go.

That’s pretty much it for terrarium maintenance items. Pretty straight forward right?

If there’s anything I missed that you still have questions about, feel free to let me know in the comments. Otherwise, feel free to check out any of the articles below to learn more about terrariums.

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