A small green world under glass that mostly waters itself.
A closed terrarium is one of the quietest ways to keep a plant. Water rises from the soil, gathers on the glass as soft condensation and drips back down like rain. Once the balance settles, you might only open the lid a few times a season. The work comes at the start: good layers, the right plants and a spot with gentle light. After that, your main job is to look in now and then and enjoy it.
Quick care card
- Light: Bright, indirect light. Never direct sun on the glass.
- Water: Rarely. A light mist only when the soil looks pale and the glass stays clear for days.
- Condensation: A light fog in the morning is healthy. Heavy streams all day mean it is too wet, so lift the lid for a few hours.
- Temperature: 60 to 78°F, away from heaters, vents and cold windows.
- Feeding: Almost never. Slow growth keeps the scene in proportion.
- Upkeep: Trim, tidy and wipe the glass about once a month.
Build it in layers
A lidded glass terrarium has no drainage hole, so the layers do the work a drainage hole would do. From the bottom up:
- Drainage layer: About an inch of small stones, pebbles or lava rock. Extra water collects here instead of around the roots.
- Barrier: A thin layer of sphagnum moss or a piece of mesh so soil does not sift down into the stones.
- Charcoal: A light sprinkle of horticultural charcoal helps keep the water fresh.
- Soil: Two to three inches of light, airy potting mix. A mix with some coco coir and orchid bark holds moisture without turning heavy.
- Top dressing: Moss, small stones or a piece of wood to finish the little landscape.
Water the soil lightly as you plant, just enough to make it evenly damp, then close the lid and watch the glass for a few days.
Choose small, humidity loving plants
The best terrarium plants stay small, grow slowly and enjoy steady moisture. Ferns, fittonia, mosses, baby tears and compact peperomias are classic choices. Our Peperomia Marble in a 3 inch pot and our Watermelon Peperomia in a 4 inch pot both slip through a 5.5 inch opening and stay compact under glass. Gently loosen the nursery soil and trim long roots so each plant sits low in the scene.
Small prayer plants and a 3 inch pilea also settle in well under a lid. You can browse every plant we've picked for glass gardens in our Plants for Terrariums collection.
Skip succulents and cacti in a closed terrarium. They want dry air and would soften and rot in the humidity. Fast growers like pothos also outgrow the glass quickly.
Light: bright but gentle
Glass magnifies heat, so direct sun can cook a closed terrarium in an afternoon. A spot a few feet from an east or north window, or near a bright window filtered by a sheer curtain, is ideal. A small LED grow light above the lid works well in a darker room. Turn the terrarium a quarter turn every week or two so plants grow evenly instead of leaning.
Reading the condensation
The glass tells you nearly everything. A light mist that comes in the morning and fades by afternoon means the balance is right. If the glass is streaming with water all day, leave the lid off for a few hours, or a full day, then close it again. If the glass stays completely clear for a week and the soil looks pale, add a few sprays of water and close it up.
Go slowly in both directions. A closed terrarium is much easier to dry out than to rescue from soggy roots.
Monthly upkeep
- Pinch off yellow or brown leaves before they decay.
- Trim any plant that touches the lid or presses on the glass.
- Wipe the inside glass with a soft cloth, and the outside with a damp one.
- Look for fuzzy white mold. Lift it out with a cotton swab and leave the lid off for a day.
Tiny white springtails sometimes appear in the soil. They are harmless and help by eating mold and fallen leaves.
Common questions
Why is there mold in my terrarium? Usually too much water, too little airflow or a decaying leaf. Remove the mold and anything dead, then leave the lid off for a day or two so the soil can dry a little.
Why are my plants turning brown and soggy? Too wet or too warm. Open the lid to dry it out and move the terrarium out of any direct sun.
Why are the leaf edges crispy? The terrarium is too dry, or the lid has been off for a while. Mist lightly and close it.
Do I ever need to fertilize? Rarely. Most closed terrariums grow happily for a year or more without it. If plants look pale after a long while, use a quarter strength liquid fertilizer once.
How long does a terrarium last? With light trimming, years. Plants that outgrow the glass can move to their own pots, and a new little plant can take their place.
Start your own
Our Asteridge Lidded Glass Terrarium and the taller Asteridge Terrarium both have a fitted glass lid and a 5.5 inch opening, made for a small humid world like this. Read our peperomia care guide to get to know your first resident, then settle in and watch the rain fall inside the glass.