Terrariums are terrific for plants that require high temperatures and extreme humidity levels. That fits the bills for thousands of succulents.
There are two types of succulents. Hardy succulents are suited to outdoor gardens and may last the year. Tropical succulents do best in a closed terrarium but as most succulents are not cold-hardy, open terrariums are better suited.
The larger the opening the terrarium has, the better the air will circulate.
Succulents only survive in terrariums when the soil can dry completely between watering. The only way to make that happen is to layer various materials.
Read on to discover the materials to use, where to place them, and how to keep them separate, which is how succulents survive in open or semi-closed enclosures.
Succulents need airflow so an open terrarium will be needed. Terrariums do not have drainage, so the first layer is gravel or sand to hold water. A substrate divider is added to keep the soil separate. A cacti soil mix is layered over the substrate divider, and then the succulents are added.
The base layer: The crucial part to get right
Inside a terrarium, condensation will accumulate. It is what keeps the humidity levels high.
The base layer is the foundations. You will need at least a 2-inch layer of drainage material. This will depend on the length of the roots of the succulents you are planting in the terrarium.
The longer the roots are, the deeper the base layer will need to be to prevent the roots from standing in water.
Suitable materials for drainage in a succulent terrarium include pebbles and gravel.
In small glass terrariums, pea gravel is ideal. In larger terrariums, use larger decorative drainage materials which can include decorative stones including river rocks in various sizes and differing textures.
Colored aquarium gravel, sand, or stones make a more interesting colorful base for the bottom of glass terrariums.
Add a filtration layer of activated charcoal or moss
Activated charcoal is not necessary, but it can be helpful as a filter as it removes toxins and helps prevent mold and mildew from building up inside the terrarium.
The cause of mold growth is overwatering, so activated charcoal will not eliminate that risk.
The main purpose of a filtration barrier between the base layer (foundations) and everything else above it is to filter water and nutrients to prevent them from lingering in the gravel base.
The filtration layer is more beneficial if you plan on watering succulents with tap water as that has contaminants in it that can cause toxins to accumulate.
Those will be trapped by activated charcoal, but it is not infinite so it will stop absorbing toxins eventually.
How long activated charcoal remains active is anyone’s guess because it depends on the amount of water passing through it.
If you decide to include a filtration layer, it only needs to be a thin layer.
Add a divider to prevent soil from falling into your drainage layer
Before adding a soil potting mix to your terrarium, a divider needs to be added to prevent the soil from mixing with the drainage layer, which will cause it to become water-logged.
Suitable divider materials include:
- Sphagnum moss
- Peat moss
- Orchid bark or fir bark
- Wood chips
You can also buy terrarium mesh sheets, which are usually just mesh netting, much like tulle (a thin netted fabric).
The purpose of substrate dividers is to prevent soil from reaching the drainage layer, so any material that will do that will work.
Consider your choice of materials because there should be about an inch depth of substrate, unless you use a mesh netting. Whatever you use, make sure it is porous because obviously, water needs to filter through it.
Some materials are slower draining than others, preferring to hold the moisture for longer.
If you do use netting, add a couple of handfuls of small pebbles or stones to weigh the material down to prevent it from folding over on itself.
Add your potting mix
The best potting soil for succulents will drain fast and provide good aeration.
If you are making a DIY potting mix, use a mix of 3 parts peat moss or coco coir, (which is a sustainable alternative to peat moss and sometimes cheaper too), with 2 parts perlite or pumice and one part wood chips or fir bark (orchid bark).
Once you have your mix ready, water it. It should crumble through your fingers when rubbed between your thumb and forefinger. It should not clump together when wet. If it does, the drainage can be improved with a 50/50 mix of sand and gravel.
Depending on the size and shape of your terrarium, the soil may need to be angled so that when your plants go in the terrarium, they are not all on a flat surface.
This is more an issue with tear-shaped glass terrariums, or large glass terrariums with the hole at an angle, rather than an open-top rectangle terrarium.
Bulking up the soil at the back of the terrarium will prevent smaller plants from being hidden. This works best if all your plants are small.
An alternative is to use different sizes of plants to create a landscape design inside the terrarium with larger plants at the back, and the smaller varieties to the front.
Plant the succulents in the terrarium
Among the best indoor cacti plants for a terrarium include the Star Cactus that grows up to 6 cm, most varieties of Hens and Chicks grow up to 4-inches tall, and the Blue Chalk Sticks plant grows up to 4-inches, too.
The Ming Thing cactus is a slow grower that can reach a height of 12-inches with a 6-inch spread, although it can be kept trimmed. This would be suited to an open-top terrarium – not a terrarium with a side opening and certainly not a closed terrarium.
The ghost plant produces leaves in the shape of a rosette and is another slow grower. This is a plant you can grow in a terrarium, remove it for propagation, replant the pups, and put the parent plant in a potted container with the same potting mix.
Many of the most popular plant varieties have dwarf types that are suited to terrariums.
As a general guideline, if the plant species require high humidity and warm dry climates, there is a good chance it will grow well in a terrarium.
As an example, among the varieties of Sansevieria, the Pinguicula would need a large terrarium (like a glass reptile enclosure) to accommodate the leaf sizes that grow up to 30cm. Whereas the Sansevieria ballyi (dwarf variety) only reaches a height of 4-inches maximum making it suitable for an open terrarium.
For a backdrop, consider the Dragons Tongue. This has leaves stretching up to 15-inches that can be kept to become new groundcover to replace decorative moss, or pruned to keep their growth in check.
As background foliage, the tongue fern (Arifolia Hemionitis) grows well in terrariums because it thrives in high humidity, suffering from curling leaves when humidity levels drop below 60%.
A range of Croton plants is also suited to growing in terrariums.
The last part is optional and it’s used to give your terrarium a ground covering to make it look like a proper mini-garden. The result is that all of the soil gets covered and it does not have to be entirely green.
For a green base, use either live moss or sheet moss. Dried reindeer moss or reindeer lichen is close to white. Live reindeer lichen is green when moist and changes color as it dries. This adds interest to the base covering in a terrarium.
To take the finishing to another level, consider adding some terrarium figurines such as miniature novelty mushrooms, mini animal kits, ornamental wildlife, or fairy garden accessories that can be anything from angel figures to ornamental ponds, wells, and mini picnic benches.
Once you have your plants inside the terrarium and the finishing touches complete, it is normal for some of the soil to be on the plants. This can be removed easily by blowing through a straw to blow the soil off the plant.
Frequently Asked Questions about planting a terrarium with succulents
Can air plants be added to a terrarium with succulents?
Air plants are epiphytes that do not need soil. The roots anchor onto the wood. To grow these in a terrarium, keep them off the soil and close to the opening to expose it to higher air movement. They can be anchored to driftwood, or sticks that are anchored into the soil.
How much space needs to be between plants?
Succulents are shallow-rooted; however, they will require at least one inch spacing between each plant to prevent the roots from crowding. Use decorative material between plants such as stones, wood, seashells, or pebbles as space fillers.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.