A terrarium is a garden inside clear glass. The first decision is whether it has a lid, because that determines which plants will live in it:

  • Closed terrarium (lidded jar or narrow-mouthed container): humid inside, with its own “rain cycle” as water condenses and runs back into the soil. For tropical and woodland plants.
  • Open terrarium (wide bowl, no lid) or dish garden: drier, with more airflow. For succulents and cacti, and any plant that dislikes constant humidity.

Penn State and Mississippi State Extension both say succulents and cacti do not belong in a closed terrarium. Mississippi State notes they would quickly rot.

Best plants for a closed terrarium

Choose plants that are naturally small and slow-growing, or that can be pruned to stay small, and that share the same light and moisture needs (University of Vermont Extension).

PlantWhy it worksSource
Nerve plant (Fittonia albivenis)Low and spreading, 8–20 cm (3–8 in); dwarf forms are suited to terrariumsNC State; Mississippi State
Spikemoss (Selaginella kraussiana)Needs high humidity and indirect light; listed as a terrarium plantNC State; Mississippi State
Creeping fig (Ficus pumila ‘Minima’ or ‘Quercifolia’)Slow, mat-forming miniature forms used in terrariumsNC State; Mississippi State
Miniature ferns: maidenhair (Adiantum), button fern (Pellaea rotundifolia)Love humidity; NC State says Delta maidenhair does well in terrariumsUVM; NC State
String of turtles (Peperomia prostrata)Small trailing peperomia; NC State lists it for terrariumsNC State
Pilea (aluminum plant, emerald ripple pilea)Small, colourful; Missouri Extension calls pileas excellent for terrariumsMissouri; Mississippi State
Polka dot plant (Hypoestes phyllostachya)Colourful leaves; used in terrariumsNC State; UVM
Miniature African violetFlowers in a terrarium; needs bright, indirect lightUVM; Mississippi State
Earth star (Cryptanthus bivittatus)Small, slow, humidity tolerant; tagged for terrariumsNC State
MossesA groundcover in large terrariums or the main feature of a small oneUVM; Penn State
Parlor palm (Chamaedorea elegans, neanthe bella)A small palm used in Mississippi State’s closed-terrarium projectMississippi State
Velvet anthuriums (miniature varieties)Many growers keep anthuriums in terraria for humidityNC State; Mississippi State

Use with care: baby’s tears (Soleirolia soleirolii) grows in terrariums, but NC State warns it will eventually crowd out the other plants.

Mississippi State Extension also lists these as suitable for open or closed terrariums: artillery fern, bead plant, flame violet, lipstick plant, rex begonia, strawberry begonia, rabbit’s foot fern, plumosa fern, small peperomias, small philodendrons and pothos, and miniature Phalaenopsis orchids.

Best plants for an open terrarium

Mississippi State Extension lists these cacti and succulents for open-system terrariums:

  • Aloe vera.
  • Burro’s tail.
  • Cacti.
  • Crown of thorns.
  • Devil’s backbone.
  • Echeveria.
  • Flaming Katy (kalanchoe).
  • Hens and chicks.
  • Jade plant.
  • Panda plant.
  • Pencil plant.
  • Aeonium.

Zebra haworthia is a good small choice. NC State notes it can be used in terrariums or small spaces such as a windowsill or desktop.

Succulents and cacti need high light (University of Missouri Extension), so give an open terrarium the brightest spot you have.

How to build a closed terrarium

Combined from Penn State, Mississippi State and University of Vermont Extension:

  1. Container: clear glass or plastic. Coloured or cloudy glass cuts the light. Wash it with soap and hot water; if you use glass cleaner, leave the lid off for a few days before planting.
  2. Base layer (optional): University of Vermont uses 2.5–5 cm (1–2 in) of coarse gravel, and Mississippi State 2.5 cm (1 in), then a thin layer of charcoal. Penn State (2026) says a rock layer is no longer thought to improve drainage and mixes a handful or two of charcoal into the potting mix instead.
  3. Soil: sterile, soilless potting mix with relatively low fertility, about 5 cm (2 in) deep or as deep as the largest root ball. Never garden soil, which is too heavy.
  4. Planting: smallest plants first. Taller plants go in the centre if viewed from all sides, or at the back if viewed from the front. Leave room near the glass. Mississippi State warns leaves resting on the glass trap moisture and invite disease.
  5. Watering in: mist lightly. Water can be added later but not easily removed.
  6. Balancing: Mississippi State suggests leaving the lid off for 24 hours, then on for 24 hours, repeating until little condensation forms. Penn State aims for condensation like “a light fog”; anything heavier means the lid should come off for a while.

Clean hands, a long spoon and a cork on a chopstick are enough tools. Penn State stresses keeping pests and pathogens out, because the humid enclosure is a perfect breeding ground.

Where to put it

  • Never in direct sun. Penn State says a closed terrarium in direct sun “will cook”. Mississippi State warns that heat builds up inside the glass.
  • Bright, indirect light. Mississippi State suggests an east-facing room with morning sun, or a west-facing one if afternoon heat is avoided. Penn State’s rule: choose terrarium plants with the same or brighter light needs as houseplants already thriving in that room.
  • Don’t keep moving it, because changes in light harm the plants (Mississippi State).

Maintenance

  • Water: only when condensation stops, plants droop or the soil feels dry (Penn State). With a tight lid, that may be every four to six months.
  • Air: Penn State notes some growers lift the lid for up to 15 minutes once a week, particularly with very tight lids.
  • Fertilizer: none for a closed system, according to Mississippi State. Slow growth is the goal.
  • Pruning: remove yellowed leaves, and trim plants that touch the glass or lid.
  • Refreshing: Mississippi State gives a typical display life of one or two years before plants outgrow the container. Penn State reports well-kept terrariums lasting nearly a decade with occasional replanting.

For other small plants, see our small indoor plants guide and peperomia varieties.

References