Soil and pots2 min read

How to make a terrarium

A tiny garden under glass, from layers to care

Open or closed

A closed terrarium recycles its own moisture: water condenses on the glass and runs back into the soil. It suits small, slow-growing tropical plants that love humidity, such as nerve plants, peperomias, pileas, spikemosses and small-leaved ferns.

An open terrarium is drier and less prone to disease. Cacti and succulents belong only in open ones, because they suffer in humid air.

Build it in layers

A terrarium has no drainage hole, so the layers do that job.

Start with a clean glass container.
Add 1–2 inches (2.5–5 cm) of washed gravel or pebbles to hold extra water away from the roots.
If you like, add a thin layer of activated charcoal to help with odors.
Add a layer of moss or fine mesh to keep soil out of the gravel.
Add at least 1.5 inches (4 cm) of potting mix, then plant.

Choose the right plants

Pick small, slow growers with small leaves that all like the same light and water. Leave out wood decorations, which can rot and grow mold. Leave room for them to fill in, and skip flowering plants in closed terrariums. No plant stays small forever, so trim or swap them as they grow.

Light

Give it bright, indirect light for at least 6 hours a day, near a north or east window. Keep it out of direct sun and away from heaters. Heat builds up fast under glass and can cook the plants.

Water and care

Water sparingly with room-temperature distilled water, and remember that a little too dry beats too wet. A closed terrarium may need water only every few months; no fog on the glass at all means it's time.

If the glass stays foggy, wipe it or leave the lid off for a while. If water pools in the gravel, draw it out with a turkey baster rather than tipping the container. Remove dead leaves right away, and don't feed for at least a year.

Sources

General guidance, not a diagnosis. Written by PlantWiz in our own words from the sources above.