There are few different reasons why you might get mold in a terrarium. In this post, you will find information on why you have mold in a terrarium and mold in terrarium soil, or fuzzy mold, and how to prevent it.
Mold (fungus) in a terrarium – reasons
If you notice mold in your terrarium, there can be few reasons why it has appeared.
Reasons for mold in a terrarium include:
- Overwatering
- Not ventilating your terrarium enough (closed or mostly closed terrariums)
- Using wrong plants for a closed terrarium
Because terrariums have no drainage holes, you have to be careful with how much water you spray or pour on plants and soil. Mixing correct plants, providing proper ventilation and not overcrowding the terrarium is also crucial.
How to remove mold in a terrarium
If you notice mold or fungus in a terrarium, you need to act immediately. That’s because it will otherwise spread and cause more damage.
Mold (fungus) will look like white fluff or webbing, and can appear in any part of the terrarium. Other types of fungus might look like black or bright spots on the plant leaves etc.
Don’t confuse mold with mealybugs, which can sometimes appear on plants. Mealybugs are small white bugs, and have a thicker look. To get rid of mealybugs on a plant, dab the cotton bud in an alcohol and dab gently to remove. If a big portion of the plant is affected, remove and replace with a healthy one.
To get rid of mold in a terrarium, you will need to carefully remove plants and all the accessories. Then, you will need to wash the container with soap and hot water to disinfect it. You should also wash any stones or other decorations.
You will then have to replace the soil and remove any affected stems, leaves or whole plants. Make sure to check the roots – prune any long or infected roots.
However, if only one part of the terrarium is affected, you might skip reconstructing the whole terrarium. You can scoop out only the affected plant and replace it with a healthy one. What is more, you can use a non-toxic fungicide to treat your plant if you wish to save it.
Or, if it’s near the soil or moss, soak the tissue in water/hydrogen peroxide and remove the affected part. Don’t water the plants after that, let it air out for few days.
Preventing mold or fungus in a terrarium
Tip #1: Make sure to have a drainage level in a terrarium
It’s crucial to have a drainage level in a terrarium to make sure to catch any excess water. Because there are no drainage holes in a terrarium, you must catch excess water in the drainage layer. This will prevent it from causing mold and other pests in the soil and on the plants, as a result.
To make a drainage, you first need to prepare your terrarium container (wash and dry it to remove any residue). Then, fill the bottom with sand or rocks. What you use for your drainage layer will depend on general design. You can pick different color rocks or sand.
Then, on top of a drainage layer, make sure to put a divider that will separate your drainage layer with charcoal level (to prevent seeping). For a divider, you can use a coffee filter, a cheese cloth or gauze, construction paper or similar. Don’t use something that will block the water from passing through the divider, though.
After the divider, goes a charcoal layer. Charcoal soaks in any impurities and helps with eliminating bad smell in a terrarium. It also helps fight mold and fungus. Then, on top of a charcoal layer, you will need to add your potting soil and plants.
Tip #2: Don’t leave water on terrarium walls for too long
Another tip to prevent mold in a terrarium is by not leaving water drops or condensation on sides of the terrarium or plant leaves for too long. Constant high humidity levels often lead to fungal and mold growth in the soil and on plants.
If you overwater your terrarium, or don’t allow air circulation, that can cause moisture buildup. Moisture droplets then accumulate on soil and plants, causing fungus and mold.
If you have a closed terrarium, make sure to open the lid once a week for around 24 hours. You can also wipe the glass from inside if condensation appears too often.
Even plants that like moisture (such as moss) will rot if the humidity is too high in the terrarium. In general, closed terrarium plants will benefit from watering once a month or less.
Tip #3: Don’t mix plants with different care requirements
When making a terrarium, make sure not to mix plants that require different care. Also, don’t use succulents and other heat loving plants in a closed terrarium, as it will lead to mold and rot.
Succulents require well draining soil that and doesn’t hold much moisture. Don’t mix succulents with air plants (however you can try to put it on top of another object instead of directly in soil), for example, or too much live moss.
Tillandsias do not require any soil at all, and in a terrarium, should be placed on dry filler to prevent mold and rot. For tillandsias, please use dry fillers such as sand, pebbles/stones, crushed coral, dry preserved moss, pumice and so on.
For example, you can mix mosses/ferns with air plants and succulents in one pot, but you will have to spray the moss so that it doesn’t dry out. If planted together, you must use an open lid container.
Don’t put succulents and air plants in a closed terrarium. Carnivorous plants need a wet soil, but also lots of heat, so use them on their own in an open terrarium.
Tip #4: Don’t water your terrarium plants too often
Make sure you water your plants in the terrarium, but don’t do it too often. Not only overwatering can lead to mold and fungus in general, but also to plant rot. Different plant types will need various amounts of watering.
In general, succulents and air plants require watering around once a week, and more often in summer and less in winter. You also need to water an open terrarium plants more often that closed terrarium ones.
Closed bowls, apothecary and lidded jars and similar need wiping or ventilating once in a while. Only water plants in closed lid jars once in 1-2 months, depending on the season and home temperatures.
You can read a guide on watering your terrarium plants here.
Tip #5: Prune plants that are overgrowing
If you have had your plant terrarium for a while and plants are overgrowing, make sure to prune them necessarily. That’s because if stems and leaves start touching the glass that often has water, they will start molding and rotting. Trim the leaves so they don’t touch glass sides.
When making a terrarium, it’s always a good idea to pick a larger jar and choose slower growing plants. Don’t pack plants too close to each other, as they will need space to grow and spread out.
Tip #6: Replace the soil
Some types of soil might have mold spores in them, causing mold to grow when you plant the plants and water the soil. If you have used the same soil for few projects and notice mold in all of them, that could indicate the soil issue.
To kill any pathogens and spores, you can bake your soil at 300 F for 30 minutes. This will sterilize the soil. Also, you can stop using the soil that you have and move to a soil less mix that is peat-based. For succulents, make sure to use fast draining soil like this.
Tip #7: Remove any dead leaves
If any of your plants have shriveled leaves for any reason, make sure to regularly remove them. That’s because fungus feeds on decaying organic matter. And if you don’t remove decaying matter in the terrarium, fungus will only spread further. You can remove any fallen leaves etc. using a long grabber tool or tweezers like this.
Thank you for reading this post! If you would like to read more on terrarium care, see this resource page.