Terrarium at Home: Open vs Closed Jars and Plants That Survive
A terrarium works when the jar and the plants want the same air: a closed jar for humidity lovers like ferns and fittonia, an open bowl for succulents and cacti. Mix the two and the succulents rot within weeks. Get that match right and the rest is layers, light and patience.
The short version
- Closed jar: ferns, fittonia (nerve plant), small pothos cuttings, moss, baby tears, peperomia.
- Open bowl: succulents, small cacti, haworthia, air plants.
- Jar size: 2 litres minimum for a first try; a 3 to 5 litre jar or old sweet jar is easier.
- Light: bright indirect light, never direct sun through glass.
- Water: closed jars, rarely; open bowls, a little every 1 to 3 weeks.
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Open or closed terrarium: which should you make?
A closed terrarium is a small water cycle. Water evaporates from soil and leaves, beads on the glass and runs back down. That suits plants from shady, damp forest floors. A succulent in the same jar sits in wet air day and night, and Mississippi State extension’s terrarium guide says plainly that succulents and cacti rot in closed systems.
An open terrarium is really a glass pot. Air moves, soil dries, and succulents are happy. It needs more watering, but it forgives a sunny windowsill better.
| Choice | Good for | Main risk |
|---|---|---|
| Closed jar | Ferns, fittonia, moss | Mould, overheating in sun |
| Open bowl | Succulents, cacti | Overwatering, no drainage hole |
For Pakistan and North India, a closed jar is the more reliable indoor project in summer, because indoor air in Multan or Delhi in May is so dry. Karachi’s humid air makes open bowls slightly trickier: succulents dry slowly there, so water even less.
What layers go into a terrarium?
There’s no drainage hole, so the layers make a small reservoir and keep roots out of standing water.
- Wash the jar with soap and hot water, then dry it. Any slime left behind feeds mould later.
- Drainage layer: about 2 to 3 cm (1 inch) of washed gravel, bajri or small pebbles.
- Charcoal (optional): a thin sprinkle of horticultural charcoal, about half a centimetre. It helps keep the water from smelling stale in closed jars. Skip it in an open bowl.
- Barrier (optional): a piece of dry moss or mesh so soil does not wash into the gravel.
- Soil: about 5 cm (2 inches). For closed jars use regular potting mix lightened with a little sand. For succulents use half potting mix, half coarse sand or grit.
- Plant: make holes with a spoon handle, drop small plants in, firm gently. Keep leaves off the glass.
- Water: mist the glass and the root balls. It is easy to add water and almost impossible to take it out.
The first week trick for closed jars
Leave the lid off for an hour each day for the first week, or alternate a day closed and a day open, until the glass shows only a light mist in the morning and clears by afternoon. That’s the jar telling you the moisture is balanced. Heavy drops running down all day mean too wet: open it for a few hours.
Which plants survive in a jar?
Closed jar
- Fittonia (nerve plant): the classic. Wilts dramatically when dry, recovers within hours.
- Small ferns: button fern, maidenhair. Maidenhair hates drying out, so a closed jar is ideal.
- Moss: collect a small patch from a damp, shaded wall after the monsoon. Rinse off insects.
- Pothos or money plant cuttings: grow fast; trim them often or they fill the jar. Money plant is toxic if chewed, so keep the jar away from toddlers.
Open bowl
- Haworthia, echeveria, small aloe, sedum, small cacti, jade cuttings.
- They want 3 to 4 hours of bright light; a terrarium on a dim shelf turns succulents pale and stretched.
Need more low light ideas? Our windowsill herbs for low light guide shows how much light a typical window really gives.
Why is there mould in my terrarium, and how do I fix it?
White fuzz on soil or a grey coat on a dying leaf means too much water and too little air. Fixes, in order:
- Remove dead or yellow leaves with long tweezers right away.
- Scrape off the fuzzy patch with a spoon.
- Leave the lid off for 1 to 2 days.
- If it comes back, add a pinch of springtails (tiny soil insects sold by terrarium shops) or rebuild with fresh soil.
Some white threads on new wood or bark in the first fortnight are harmless fungus and fade on their own. A sour smell is not harmless; that is rot, and the jar needs drying.
Where should a terrarium go?
Bright, no direct sun. Glass traps heat fast, and a closed jar on a south windowsill in April can cook its plants in one afternoon. An east window or a bright room a metre from a window is ideal. In winter, don’t put jars on a cold sill in Islamabad or Lahore at night; condensation turns to cold wet soil and roots sulk. Turn the jar a quarter turn every week so plants grow straight.
How often should you water a terrarium?
- Closed: almost never once balanced. If the glass stays clear for several days and soil looks lighter, mist 5 to 10 sprays.
- Open succulent bowl: water only when the soil is dry right through, usually every 1 to 3 weeks. Use a spoon or syringe at the base, not over the leaves.
Fertiliser is mostly unnecessary. You want slow growth in a jar. A quarter-strength liquid feed once in spring is plenty for an open bowl.
Glass jars break; keep large ones off edges where children play. Money plant, dieffenbachia and some ferns sold for jars are irritant or toxic if chewed by kids or pets; check our poisonous plants list before choosing. Wash hands after handling moss collected outdoors. If a child eats soil or plants and has vomiting, mouth swelling or drowsiness, call a doctor straight away.
Terrarium questions, answered
How do you make a terrarium step by step?
Wash a glass jar, add gravel, an optional thin charcoal layer, then 5 cm of soil, plant small humidity or dry loving plants to match the jar, and mist lightly. Balance moisture in the first week.
What plants are best for a closed terrarium?
Fittonia, small ferns, moss, peperomia and baby tears. They like steady humidity and low to medium light, which a closed jar gives them.
Can you put succulents in a closed terrarium?
No. Constant humidity rots succulents and cacti. Put them in an open bowl with gritty soil and good light.
Do I need activated charcoal in a terrarium?
It’s optional. A thin layer helps closed jars stay fresh smelling. Open succulent bowls don’t need it at all.
How long does a closed terrarium last?
Many last a year or two with occasional trimming. Some go much longer. Plants that outgrow the jar can be trimmed or swapped.
Why is my terrarium foggy all the time?
There is too much water. Open the lid for a few hours a day until the glass clears by afternoon.
What jar can I use for a terrarium?
Any clear glass with a wide enough mouth for your hand or tools: a big sweet jar, a pickle jar, a fish bowl. Avoid tinted glass, which cuts light.
Do terrariums need sunlight?
They need bright light but not direct sun. Direct sun through glass overheats the inside within hours.
Are there bugs in terrariums?
Sometimes fungus gnats or springtails appear. Springtails are helpful and eat mould. Gnats mean the soil is too wet.
More indoor ideas sit in our Phool aur Paudhe section, and the potting mix guide covers soil blends for every pot.