The Closed Terrarium Care Journal
Botanical Boys
The Care Journal
A closed terrarium is a world of its own
Once settled it needs very little. The secret is simple — observe often, and act in small changes before anything gets worse.
Start here
The essentials
01
Lighting & Temperature
Every home is different. Terrariums do best in a bright room with plenty of natural light — but keep them out of direct sun on the glass. Direct sunlight overheats the inside, causes heavy condensation, and stresses the plants. A normal room temperature of around 19–21°C is ideal.
02
Condensation
Your terrarium recycles its own moisture: the mosses and substrate hold water and release it through a natural humidity cycle, which is why we don’t add extra water when we build them. A little condensation on the glass is normal and healthy. If it’s so foggy you can’t see the plants, there’s slightly too much moisture — lift the lid for a couple of hours, then close it again. Aim for a faint mist, never soaking wet. In a very dry home, air it far less often.
03
Watering
A terrarium has no fixed schedule like a potted houseplant — it’s all about observation. The free-draining soil should never be wet. If leaves start to wilt and the moss turns pale, open the lid and feel the soil; if it’s dry, give a small drink. Use a spray jet, pipette or syringe and water at the base of the plant, avoiding the leaves. Replace the lid and watch over the next few days. Most of our terrariums need watering only a couple of times a year.
If something looks off
Troubleshooting
Tap any symptom to see what to do.
White mould or fungus on the soil +
Usually harmless saprophytic fungi — a natural part of a humid ecosystem that breaks down organic matter.
Air the terrarium a few hours a day for a few days, scoop out the white patches with tweezers or a spoon, and check you aren’t overwatering. A light sprinkle of ground cinnamon is a natural antifungal if it persists. Add springtails to naturally reduce mould and recycle organic matter
Fungus gnats (small flies) +
Tiny eggs that hatch deep in the soil — common in houseplants.
Sprinkle organic gnat powder just under the top layer of soil, and use sticky traps to bring the population down.
White fluff on the leaves +
Mould from airborne spores or too much humidity.
Open the lid and wipe the mould off early. Prune any leaf that’s already damaged so it doesn’t rot. Then leave the lid off a couple of hours for air to circulate — but not so long the plants dry out.
Mushrooms growing inside +
A sign of rich soil and a healthy, thriving ecosystem.
Leave them be — they naturally die off within a couple of weeks. No action needed as long as your plants look healthy.
Plants growing too tall +
Healthy growth reaching for more space.
Open the lid and prune the stem just below a node (where a leaf joins the stem), a couple of leaves down, to encourage fuller growth.
White spots on a bonsai trunk +
Small specks of surface mould.
Open the lid for a few hours to air out, and wipe the spots off the trunk with a clean cloth.
Plants look weepy, dry & pale +
The terrarium needs a drink — more often if the lid seal is loose.
Test the soil with your finger. If it’s dry, water the base with about 2–3 tablespoons of filtered water (tap is fine, but may leave scale marks on the glass over time).
Freshly built & settling in +
A new terrarium needs time to find its balance.
Be patient through the first few weeks — observe daily and make small adjustments. Not every terrarium is guaranteed, but most settle into a self-sustaining cycle.
The cast
Plant directory
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Fittonia
“Nerve Plant”
Colourful, nerve-like veined leaves. Loves dappled shade and moisture — but never wet.
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Bun Moss
Cushion moss
Hill-shaped cushions of true green. Keep moist — its moisture feeds the whole terrarium. Trim any brown bits.
Chamaedorea
“ground gift” · Parlour Palm
A tropical look and feel. Enjoys high humidity but not soaking wet; prune occasionally as it grows tall.
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Ficus Ginseng
Ginseng fig tree
A little tree that loves humidity and rarely needs water. Snip bushy stems to shape — a milky latex seals the cut.
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Polyscias
“many shade”
A woodland-feel tree that tolerates shade well. Likes humidity, needs little water; prune back if it gets too tall.
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Pilea
“Friendship Plant”
Tropical, humidity-loving and easy-going. If it trails too far, simply prune it back.
Plant photographs sourced from Wikimedia Commons (CC BY / CC BY-SA). Swap in your own product photos any time.
Once a year
Annual care
- ✓Clear out any dead leaves and give it a general tidy.
- ✓Replace any plants or mosses that haven’t made it — though good daily observation should keep this rare.
- ✓Clean larger decorative stones if green algae appears.
Need a hand?
Terrarium A&E
Our plant-care and design service. After your 30-day guarantee we can replace a single plant or completely redesign your terrarium.
Email help@botanicalboys.comEvery purchase includes a 30-day guarantee with free replacement plants if needed. Botanical Boys cannot guarantee plant lifespan and is not responsible for a terrarium once it leaves our store; this guide reflects our own experience and research. Enjoy your beautiful terrarium garden. Plant photographs sourced from Wikimedia Commons (CC BY / CC BY-SA). Swap in your own product photos any time.
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