What makes a houseplant suitable for a terrarium
A terrarium is a small, enclosed or semi-enclosed container, usually glass, where humidity stays higher than in the rest of the room. The plants that tend to do well share a few traits:
- Small or slow-growing. A plant that quickly fills the container will need constant trimming or replacing.
- Comfortable with humidity. Many tropical understory plants, which grow in the shade of larger plants in the wild, fit this description.
- Tolerant of low to medium indirect light. Glass can magnify direct sun and overheat the container.
- Shallow roots. Terrarium soil is usually only a few centimeters deep.
Match the plants to each other as well. Mixing a moisture-loving fern with a plant that wants to dry out between waterings usually means one of them struggles.
Open vs closed terrariums
Closed terrariums have a lid or a narrow opening that holds moisture in. Water evaporates, condenses on the glass, and drips back down, so they often need very little watering. They suit moisture-loving plants such as ferns, nerve plant, moss and Selaginella.
Open terrariums are bowls, vases or containers without a lid. Air moves freely and the soil dries more quickly, so they need more regular watering and suit plants that like a little more airflow, such as many peperomias and some small bromeliads.
If you are unsure, start with a container you can open. A closed container that stays foggy all day, or grows mold, can be vented for a few hours.
Good terrarium plants
Availability and exact varieties differ by seller, so use these as starting points rather than a fixed list.
- Nerve plant (Fittonia). Small leaves with pink, white or red veining. It likes humidity and moist soil and is commonly recommended for beginners. It tends to wilt dramatically when dry and often recovers after watering.
- Peperomia. Many peperomias stay compact and slow-growing. Because their leaves are semi-succulent, they usually prefer less moisture than ferns, so they often suit open containers better than tightly sealed ones.
- Small ferns. Button fern and rabbit’s foot fern are often mentioned, as are other compact types. Ferns like even moisture and humidity. For larger fern species, see our guides to autumn fern care indoors and lady fern plant care; both are too big for most jars.
- Moss. Cushion moss and sheet moss make a living carpet that helps hold moisture and covers bare soil.
- Selaginella (spike moss or club moss). A fine-textured, moss-like plant that likes humidity and dislikes drying out.
- Creeping fig (Ficus pumila). A fine-leaved creeper that clings to rocks and glass. It can grow quickly, so expect to trim it.
- Small bromeliads and earth stars. Cryptanthus are low, rosette-shaped bromeliads with patterned leaves, often grown in terrariums. See our pink star plant care guide for more on these.
- Small Pilea and baby tears. Compact, humidity-friendly plants sometimes used as ground cover. Check each one’s expected size before buying.
Can string of pearls be grown in a terrarium?
Usually not in a closed one. String of pearls (Senecio rowleyanus) is a succulent that prefers bright light and soil that dries out. The trapped, humid air in a closed terrarium tends to cause rot in succulents and cacti. Some growers keep succulents in a very open, dry container with gritty soil and plenty of light, but that is a different setup from a humid tropical terrarium, and the two should not be mixed in one container. String of pearls is also generally listed as toxic to pets and people if eaten, so keep it out of reach.
What not to put in a terrarium
- Succulents and cacti in a closed container. They tend to rot in constant humidity.
- Large, fast-growing houseplants. Monstera, large philodendrons and full-size pothos often outgrow a small container quickly. Young cuttings may look fine at first but need regular pruning.
- Plants with very different needs. A plant that wants dry soil and one that wants constant moisture should not share a container.
- Plants collected from the wild or from other people’s gardens. They can bring in pests, mold or fungal problems. Use healthy nursery plants and check the leaves and soil.
- Cut flowers and decaying material. Rotting plant matter encourages mold and gnats.
The four layers of a terrarium
Descriptions vary, but a typical build has four layers from the bottom up:
- Drainage layer. A few centimeters of small stones, gravel or expanded clay to hold excess water away from the roots.
- Barrier layer. A thin layer of mesh, or sometimes moss, to keep soil from filling the gaps in the drainage layer.
- Charcoal (optional). Many builders add a thin layer of horticultural charcoal to help keep the container fresher. It is not strictly required.
- Substrate and plants. A peat-light or well-draining potting mix suited to the plants, topped with moss or decorative stones.
Containers without a drain hole are easy to overwater, so keep the drainage layer proportionate to the container and go lightly with water.
Light, watering and airflow
- Light: Bright, indirect light is a safe starting point. Avoid placing a closed terrarium in direct sun; the glass can heat up and scorch leaves.
- Watering: Add water in small amounts. In a closed container, a few sprays or a small pour may last weeks. If the soil is waterlogged or the glass is permanently fogged, you have added too much.
- Airflow: Open the lid for a while now and then to reduce mold and freshen the air, especially if condensation never clears.
Pruning and maintenance
Trim leggy growth and any leaves that touch the glass, as they tend to rot. Remove dead leaves promptly. A pair of long tweezers or small scissors makes this easier in a narrow container. Fertilizer is rarely needed and can cause fast, weak growth; if you feed at all, use a very dilute solution.
Troubleshooting
- White fuzzy mold: Remove the affected parts, reduce moisture and vent the lid.
- Constant condensation: The container is too wet or too warm; open it for a while.
- Leggy plants leaning toward light: Rotate the container or increase indirect light.
- Mushy stems or leaves: Usually overwatering or too much humidity for that plant. Remove rotting parts and replace the plant if needed.
- Tiny flying insects: Often fungus gnats from wet soil. Let the soil dry out and avoid overwatering.
Pet and child safety
Many plants used in terrariums are not safe to eat, and children and pets can knock over or open glass containers. Keep terrariums out of reach.
- Do not assume a plant is safe because it is small. Pothos, string of pearls, creeping fig and begonias, for example, are commonly listed as toxic to pets if chewed or eaten. Peperomia, Fittonia and many ferns are often listed as non-toxic, but listings differ by species and source.
- Check each plant’s name against a reliable pet-safety source such as the ASPCA plant list before you buy, and contact a veterinarian or poison control service if a pet or child eats a plant.
- If you keep reptiles or amphibians, see our guide to the best plants for vivariums, because animal enclosures have different requirements.