The practice of watering a terrarium seems like a simple one.
Water + Terrarium = Win?
But honestly, it’s one the most common questions people have about caring for terrariums, and it’s something plenty of people seem to get wrong.
After all, terrarium ecosystems operate on a fine balance. Too much or too little water can both have dire negative impacts.
Too much and you’re risking rot and mould. Too little and well… things die.
Every terrarium is going to have different watering needs, but there are some common practices to follow to have the best chance of getting it just right.
So put down the hosepipe and take a look at the right way to water a terrarium.
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When to Water a Terrarium
Knowing precisely when to water a terrarium is half the battle.
We often hear of people’s terrariums going months without a top up, whereas I find it hard to leave them alone that long. Just a little water more won’t hurt right?
We’ll add “just a little more” again and again till its become a holiday home for Shrek.
Thankfully, there are plenty of indicators to look out for, and you shouldn’t be adding more water to your terrarium unless at least one of these is present.
Most terrariums are going to be housing tropical plants that require lots of moisture to thrive. For this, a substrate with high water retention but good drainage is critical.
So generally speaking, the substrate should never be dry.
The first and most obvious way of testing is to just get your hands dirty and feel it!
Tropical terrarium substrate should be moist to the touch, but never soggy.
Or, (if you don’t want to get your hands dirty) you can check the condensation levels against the glass through the substrate level. An evenly moist substrate will show beads of condensation throughout the whole layer.
No Visible Condensation
It’s not just the substrate level that should show condensation. A closed terrarium with an effective water cycle should display some condensation throughout the container at certain points throughout the day.
Generally during the morning and midday sun, when temperatures are at their highest.
Here you’ll see some misting up of the glass.
As noted earlier, if you can see condensation through the substrate layer, then there’s some moisture there.
However, if there’s no condensation throughout the top of the terrarium, that’s a strong sign that there’s little to no humidity and likely insufficient water in the system as a whole.
Crispy, Yellowing or Wilting Leaves
Finally, just check your plants.
Hopefully you’ll be able to fix any dryness issues before your plants start to suffer, but if you spot any of these then there’s a good chance you need to add more water immediately.
Most plants are going to indicate if they’re struggling with a lack of water. The most common negative indicators to look out for are to be found with the leaves.
Of course, every plant is different, but these are pretty universal.
Some plants are far more sensitive than others to watering. For example, Fittonia are the damsels of the plant world and are prone to fainting at the first sign of dryness.
So take care that you don’t overwater your whole terrarium whilst trying to keep one particular plant happy. It’s important to understand the needs of individual plants to get your watering system perfected.
How Often to Water a Terrarium
There is no single fit watering schedule for terrariums.
There’s a balance to be struck between little and often, and few and far between.
On one hand, adding just a little at a time will make sure you’re not overwatering the plants or grossly oversaturating the substrate. But by constantly opening up a closed terrarium to add water, you’re never letting it settle into a healthy water cycle of its own.
How often to water your terrarium depends on your terrarium size, materials, plants and environmental conditions.
That being said, provided you’ve added the right amount of water to sustain a healthy water cycle, you can have a rough idea of when you might need to add to it.
Starting with once a month, then pushing it further if you find it doesn’t need it.
How to Water a Terrarium
Watering a terrarium is a lot like playing Rock, Paper, Scissors.
It’s deceptively simple to play, involves a large degree of guesswork, and it’s very easy to get wrong.
Which is why we take a considered approach to watering.
Misting is Best
Using a mister/atomiser or simple a water bottle with a spray function is always recommended.
If you glug water out of a bottle or a tap directly, you’re likely to flood some areas of your terrarium and neglect others.
For the most part, you want an even distribution of water. If some local areas have more water demanding plants then you can directly add more water by spraying that area directly, or pipetting some water directly on top of them.
I also like to spray the insides of the container a little. It tends to trickle down deeper and helps fill the reservoir if its bone dry. It also cleans off any dirt that’s picked up the sides.
At first, I started using a fancy little mister but found it sprayed deceptively little water.
These days I just recommend a high quality spray bottle with an adjustable nozzle.
Adding the Right Amount of Water
Knowing when to stop adding water is what I find the most difficult.
Watering my plants feels like I’m showing them love, and I have a lot of love to give…
Generally, the idea is to evenly saturate the substrate with water, but leave no area sodden and no standing water on top, or below the substrate layer.
If you have a false bottom, it’s usually fine if there’s a small amount of water that seeps through to the pebble (or LECA) base. It helps to maintain the humidity and as long as the water doesn’t reach the substrate, it won’t wick up and risk rotting the roots.
To achieve the best saturation level, it’s best to add a moderate amount of water at a time, and then leave the moisture to permeate. If you try to go from dry to perfectly saturated in one go, it’s easy to overdo it (and much harder to correct).
Which Water to Use
Water straight from the tap isn’t ideal for terrariums.
Chlorine isn’t great for plants, but at the levels present in tap water, it’s unlikely to do much damage. You can always let tap water sit for 24 hours to let the chlorine evaporate off.
The real issue is the salts found in tap water. Again, they’re unlikely to harm your plants, but they can leave white streaks on your container over time. Not harmful, but not ideal.
Thankfully, there’s a few types of suitable water that we can buy.
- Reverse osmosis water – ultra pure, but ultra expensive.
- Distilled water – next level down, very pure but still fairly pricey.
- Deionized water – water with the salts removed. Tends to be sold for use in car batteries and is much cheaper. I buy this in bulk.
Over to You
How do you water your plants?
Honestly, getting terrariums perfectly balanced can be fairly challenging. In our Essential Guide to Tropical Terrariums, we break it all down, from plant pairing to substrate, build and care, we make every part of the process easy for you.