Terrariums are interesting and long lasting mini plant gardens/decorations. However, some mistakes in making or caring for a terrarium might make it go bad and plants to die too fast. So why is my terrarium dying? In this post, you will find reasons of why terrariums die and what you can do to fix and prevent those issues.
Few of the main reasons why terrariums are dying include overwatering the plants or soil, using wrong containers for terrariums, mixing plants with different requirements, positioning terrariums in wrong spots.
Reason #1: Overwatering plants or soil
Overwatering plants in the terrarium is one of the most common mistakes and reasons why terrariums start dying. Too much water will cause mold growth and plant rot. That’s because most terrarium plants don’t need much watering. Plus, terrariums lack drainage holes, which makes plants susceptible to rot.
Signs that you have been overwatering your terrarium plants are discolored brown or white leaves. Leaves might also lose their firmness and become soft in succulents. If a plant starts rotting, leaves and stem might look as if they are melting from softness.
To confirm that you have been overwatering your succulent plants, look at their roots. Rotting roots will be brown and not normal white/yellowish.
If some roots of your plant are brown, you can save the plant by removing those affected roots. But if the plant feels soft and is crumbling, that means it has rotted. Roots will be brown too.
In air plants, rotting and overwatering is not as common as in succulents. That’s because they are not planted in soil and mostly take as much water as needed.
But you have to make sure that air plants dry out completely after watering (turn upside down to dry if soaking). Don’t leave water between leaves either.
You can read a terrarium watering guide here.
Reason #2: Putting plants in wrong containers
When making a terrarium, make sure you only use suitable plants in specific containers. There are open and closed containers, and you cannot grow most plants in closed terrariums.
For example, all succulents, including cacti, can only be planted in an open terrarium. That’s because succulents come from hot parts of the world, where they have fast draining soil, good ventilation and low humidity levels. Don’t use succulents for closed terrariums.
Same is with air plants. Air plants need proper watering once a week or so, but they must have good air exchange. Closed terrariums don’t provide that, so your tillandsias might die in a closed terrarium.
Carnivorous plants require a terrarium to be at least somewhat open. Even though they like wet soil, they need high heat – which you can’t provide in closed terrarium. If direct light hits the terrarium, it will cook the plants inside.
The best suited plants for closed terrariums are mosses, lichen, ferns, some tropical plants. You can find a list of plants for closed and open terrariums here.
Reason #3: Mixing plants with different requirements
Because plants have different care requirements, you cannot mix some of them together. For example, you can mix different types of succulents as their care is somewhat similar.
However, don’t mix carnivorous plants with other types of plants. Carnivorous plants need higher light, more water, and a winter dormancy period. You can mix mosses/lichen with carnivorous plants.
You also shouldn’t mix live moss (there are non-living mosses which are fine, such as reindeer moss) with plants that require dry conditions.
However, if you are more experienced with plants, you can create a mixed plant terrarium. For example, you can mix succulents and mosses or air plants together.
But in this case, you would have to raise the succulents in separate pot in a terrarium so that its soil can drain properly. You would also have to mask it to make it visually pleasing.
Reason #4: Plants are too big
Yes, if your plants in a terrarium get too long, there’s a higher risk of them dying. That’s because long plants will touch the sides of the terrarium and catch water that can lead to plant rot.
If your plants get too long or big, make sure to prune them a little. It’s always a good idea to choose slower growing plants for a terrarium.
If your succulents start becoming thin and leggy, this can indicate lack of sunlight. Solve by placing the terrarium in a bright but indirect light. Leaning to one side means that you need to turn your terrarium once a week or so to allow all parts of a terrarium to get enough sunlight.
You can read a terrarium plant pruning guide here.
Reason #5: Too much fertilization
Avoid fertilizing plants too much as it will lead to faster growth. Carnivorous plants for example, can die because of strong fertilization, as they naturally grow in poor nutrient soil and feed on insects instead.
You don’t need to fertilize most terrarium plants. If you wish, you can fertilize your air plants once in 2 months with higher nitrogen and potassium fertilizer.
There are sprays, that you can use more frequently and spray plants directly in a terrarium, like this. They are usually great to use during growth period.
Reason #6: Lack of light
Most terrarium plants do need bright but indirect sunlight. Succulents, air plants and carnivorous plants need lots of bright, but indirect light. Mosses also need indirect light, but as much. If you see any black leaves, it can indicate low light and overwatering.
Lack of light will lead to wilting, discolored leaves. Succulents will start tilting to one side, or grow thin stems (to ‘stretch’ and get more light). Southern facing windows are better for bright light during the mid day. Western facing windows will receive a lot of light, but you can place your terrarium away from direct light.
If you don’t have enough lighting in your room, you can get artificial light to keep your plants happy. Lights that you can use for your terrarium are fluorescent and LED lights like this. Place the fluorescent light around 10 inches (25 cm) away from your terrarium, and around 20 inches (51 cm) away from LED lights.
You should place the light even further away, just to create a well-lit area. If you place the light too close, it will promote faster growth, which you don’t need for terrarium plants. Remember, your aim is to create bright conditions without much direct light.
You can also choose a compact fluorescent bulb (CFL) in a desktop lamp if you have one to few terrariums. Position the light bit further away as it can get intense when positioned too closely.
Reason #7: Too much light & heat
Your terrarium plants can start dying due to too much light and/or heat. For example, you must not place your terrarium where direct unfiltered light hits it for more than an hour. While you can put your terrarium near the window, don’t put on a windowsill with full sun.
Instead, place it a bit away, that it’s in a bright light without any direct light hitting it. If you are using artificial light, follow guidelines about the distance from the light to your terrarium. Signs of too much light and heat are dry dead leaves.
Also, make sure not to place your terrarium near a hot radiator. Too much heat can quickly kill your plants in the terrarium. If you would like to read more tips on how much light terrariums need, see this post.
Reason #8: Under watering
If you are underwatering your terrarium plants, they can start dying. Sometimes it might be hard to know how much water to give your terrarium plants, and many people make mistakes here. That’s normal, and all part of a learning experience.
Signs that you are not giving enough water to your plants are falling leaves, shriveled and dry leaves, brown spots on leaves. Under watered air plants, for example, develop dry and crispy leaves. Yellow leaves also indicate under watering. Remove any yellow leaves as they won’t become green again.
Succulents for example, store water in their cells, and when they have enough water, plant is hard and firm, standing straight in its full form. When the plant lacks water, it loses the internal pressure, become soft and can even fold.
Before watering your succulents, feel the soil and make it’s dried up before watering again. In general, you should water around once a week (with around a quarter cup of water for small-medium containers) in summer. In winter, water once in around 2 weeks.
Carnivorous plants love a lot of water in the soil. So, make sure to water the soil 1-2 times a week, depending on the season. Only use distilled or bottled water, as carnivorous plants are very sensitive to water quality (chemicals, pollution etc.).
Air plants can be watered in few ways – by submerging, rinsing and misting. If you wish to learn more about watering air plants, please see this post.
Reason #9: Lack of terrarium care
To make sure that your terrarium can live for a long time, you still need to care for it from time to time. And it doesn’t just include watering. Make sure to clean the terrarium glass from inside if you see any dirt etc.
If your terrarium fogs up from time to time, it’s fine. But if there are constant water drops, make sure to open the terrarium lid once a week for a day or wipe it with a tissue.
Also, make sure you remove any dead leaves etc. from your terrarium as soon as you see them. That’s because it can lead to mold and fungi development, as they feed on decaying organic material. That’s when you can see mushrooms growing in the soil – but actual mushrooms are not harmful to your plants.
You can read more on mushrooms in the terrarium here.
What is more, make sure to remove any mold that you see as soon as possible. Otherwise, it can spread to other parts of the plant and kill them too.
If a plant is only partially affected, you can cut off the affected part and replant. But if it feels soft and most of the plant’s body is rotted/moldy, discard and use a new healthy plant.
If you don’t remove any dead leaves and overwater the soil, you also risk getting fungus gnats (small flies) in your terrarium.
Reason #10: Lack of air circulation
If you don’t allow air circulation, your terrarium will start fogging up, and plants can start rotting and dying. This is especially true for succulents (including cacti) and air plants.
Succulents and air plants require good air circulation, to make sure that soil is drying up and there’s no water trapped between their leaves. Carnivorous plants love bright light, but without good air circulation (in a closed terrarium), they will be cooked due to high heat.
So, make sure to plant them in open terrariums. Carnivorous plants can be planted in a more sealed terrarium, but it must have an opening for your plant to last long. Read more on carnivorous plants here (new tab).
Reason #11: Not adding a charcoal layer
When you make a terrarium, you must add a layer of charcoal on the bottom. Because terrariums have no drainage holes, excess water cannot come out. Also, air exchange in a terrarium is limited, as is space for plants.
Charcoal layer will help fight any fungus & mold, keep the terrarium clean and absorb bad smell. It acts as a purifier, which is essential in a small enclosed space.
If you are making a succulent terrarium, you need have layers in this order:
- Filler/drainage – sand or stones of any variety or color
- Separator – coffee filter, construction paper, cheesecloth etc.
- Activated charcoal layer
- Soil mix
- Plants and decorations
If you are making a terrarium with air plants, you won’t need to use a charcoal layer or soil. The best thing is to mist air plants moderately or take them out for soaking or rinsing if possible. Layers for air plant terrariums include only a dry filler (sand, stones, wood, dry preserves moss etc.) and plants with decorations.
To summarize, you should use a charcoal layer for all plants that need soil and watering in the terrarium. If you don’t have a charcoal layer in a terrarium, it is more likely to start dying sooner.
Reason #12: Using wrong type of soil
Different types of plants need to be planted in different types of soil. For example, succulents (including cacti) need a faster draining and porous soil. The best choice is to use a succulent and cacti soil mix like this. For succulents, you can also use a palm or citrus potting mix.
Air plants don’t need to be put in soil, and make sure that any filler under them is dry. Any wet or moist medium will cause rot of the plant.
Carnivorous plants need soil that can retain water, but also allow proper drainage. You can find ready mixes, which often include peat moss, vermiculite, perlite. Don’t use general potting soil for growing carnivorous plants, or they won’t last too long. And only water with distilled, bottled or reverse-osmosis water.
Thank you for reading this post! If you would like to learn more on terrarium care, see this resource page.