Plants that stay small and cope with life under glass

A terrarium plant needs three qualities: it must stay compact, tolerate low light, and cope with its container's humidity regime. It's this last point that rules out most candidates. Under a closed cloche, the air stays saturated and water sits right at the surface of the substrate: tropical woodland plants thrive there, while succulents rot within weeks.

For a closed terrarium

Fittonias, with their white or pink veins, are the classic starter plant: they signal a lack of water by drooping, then perk back up within hours. Spikemoss forms a dense green carpet that covers the terrarium floor. Small ferns, such as bird's nest fern or maidenhair fern, add height and delicate fronds. All are planted from 5–6 cm pots, small enough to fit through a narrow neck. The Which plant for a terrarium comparison sets out the pairings that last.

For an open container

Succulents want the opposite: plenty of light, a very free-draining mineral substrate, and moving air. Echeverias, haworthias and small cacti can be mixed together in a container that's never closed. The succulent terrarium tutorial shows the full build.

The first few weeks

Plant close together without compacting the substrate, and mist lightly at set-up rather than watering. The roots take two to three weeks to settle in: this is the period to intervene the least. Remove yellowing leaves as they appear, as they would go mouldy under glass. Mosses round off the scene and signal the humidity level better than any sensor.