Terrarium Making: A Beginner's Guide
A terrarium is a tiny, self-contained garden under glass — and one of the lowest-commitment ways into plants, because a well-built one mostly takes care of itself. This guide covers the one decision that drives everything (closed vs open), exactly what to buy, the layers that keep it alive, and how to build your first one in an afternoon.
- There are two kinds: closed terrariums (sealed, for humidity-loving plants like ferns and moss) and open terrariums (for succulents and cacti). This one choice drives everything else.
- A closed terrarium recycles its own water and can go weeks to months between waterings; an open one needs a small drink every week or two.
- The layers matter: drainage → charcoal → barrier → substrate. Skip them and water pools at the bottom and rots the roots.
- Best first plants: fittonia, ferns, and moss for closed; haworthia, jade, and other succulents for open. Never mix the two.
- It's a cheap, fast win — a glass jar, a few handfuls of materials, and 2–3 small plants, built in an afternoon and alive for years.
What a terrarium actually is
A terrarium is a small garden grown inside a glass container — and one of the lowest-commitment ways into plants, because a well-built one mostly looks after itself.
The science is simple and a little magical. In a closed terrarium (a sealed jar or lidded bowl), the plants and soil recycle their own moisture: water evaporates, condenses on the glass, and trickles back down into the soil. It's a miniature water cycle under glass. The most famous example — David Latimer's sealed bottle garden in England — has been watered exactly once since 1960. An open terrarium has no lid and more airflow, which suits plants that would rot in all that humidity: succulents, cacti, and air plants.
Everything else in this guide follows from one decision — closed or open — so let's settle that first.
Closed or open? Decide this first
Choose a closed terrarium if you want the lowest-maintenance option and you like a lush, jungly, mossy look. Closed terrariums suit tropical, humidity-loving plants and are nearly self-watering once they find their balance. The catch: they're easy to overwater, and they cannot take direct sun.
Choose an open terrarium if you love succulents and cacti, your space gets bright light, or you'd rather not think about humidity at all. Open terrariums dry out and need occasional watering, but they're very hard to drown and they forgive beginners who like to fuss over their plants.
The single most common beginner mistake is mismatching the two — succulents sealed in a closed jar will rot within weeks, and ferns in an open dish will crisp. Match the plant to the container and most problems simply never happen.
What you need
You can build a first terrarium for well under $30. The full list:
A clear glass container. For closed, a lidded glass jar or apothecary jar; for open, a wide bowl or geometric vessel. A wide opening makes your first build dramatically easier than a narrow neck — you need to get your hands (or tools) inside. Clear glass only; colored glass starves the plants of light.
Drainage material. A 2–3 cm layer of LECA clay pebbles or pea gravel. Terrariums have no drainage hole, so this layer holds excess water away from the roots.
Horticultural charcoal. A thin layer that keeps a sealed environment fresh and fights odor and mold. Activated horticultural charcoal is cheap and a single bag lasts for many builds.
A barrier layer. A thin sheet of sphagnum moss or fine mesh, so your soil doesn't wash down into the drainage layer.
The right substrate. Standard potting mix for tropical (closed) terrariums; a gritty cactus and succulent mix for open ones.
Plants — 2–3 small ones (specific picks below).
A few tools. For narrow jars, long tweezers or a spoon and a small brush help enormously, plus a plant mister for watering without flooding.
Never place a closed terrarium in direct sunlight. The sealed glass traps heat like a greenhouse and can cook your plants in a single afternoon. Bright, indirect light only — for both types.
Building it, layer by layer
- 1
Clean the glass
Wash and dry the container thoroughly. Soap residue or dust shows through glass, and in a sealed environment any leftover grime can encourage mold.
- 2
Lay the drainage base
Add 2–3 cm of LECA or pebbles. This is the reservoir excess water drains into instead of sitting around the roots. Tilt it slightly higher at the back for a layered, scenic look.
- 3
Add charcoal and a barrier
Sprinkle a thin, even layer of horticultural charcoal over the stones. Then lay your sphagnum-moss or mesh barrier on top, so the soil above stays separate from the drainage below.
- 4
Add the substrate
Add 3–5 cm of the right soil — potting mix for tropical, gritty cactus mix for succulents — deeper at the back if you want height. Make it deep enough that roots sit comfortably below the surface.
- 5
Plant from largest to smallest
Dig a hole for your biggest plant first and work down to the smallest, firming soil around each root ball. Leave gaps — they fill in as they grow. For tight jars, lower each plant in with tweezers.
- 6
Decorate, water, and place
Add moss, stones, or a small figure. Mist a tropical setup until the soil is just damp (don't soak it); give a succulent setup a light drink. Fit the lid on a closed terrarium, leave an open one open, and set it in bright, indirect light.
The best beginner plants
For a closed terrarium (humidity lovers): fittonia (nerve plant) for a pop of color, a small button fern or maidenhair fern, moss for groundcover, baby's tears, peperomia, and pothos or creeping-fig cuttings that root happily in the damp. All of these thrive on humidity and indirect light.
For an open terrarium (dry lovers): haworthia, echeveria and other rosette succulents, jade, small cacti, and air plants (which need no soil at all). These want airflow and bright light and hate sitting wet.
Whatever you pick, buy small — 2-inch nursery plants are cheaper, easier to arrange, and grow into the space. Three small plants in a medium jar is plenty: crowding looks lush on day one and a tangled mess three months later.
Keeping it alive
Light: bright but indirect for both types. Direct sun turns a closed terrarium into an oven and scorches the leaves inside.
Watering a closed terrarium: only when the glass stops fogging and the soil looks dry — often just every few weeks to months. When in doubt, wait.
Watering an open terrarium: a small drink every 1–2 weeks, letting it dry out between. Succulents die from too much water far more often than too little.
Read the condensation. A little fog on the glass is healthy — the water cycle working. Heavy fog every day means it's too wet: take the lid off for a day to dry out.
Mould means too much moisture or too little airflow. Remove the affected bits, leave the lid off for a few days, and ease off the water. The charcoal layer is your main defense.
Skip the fertilizer. Terrariums are meant to grow slowly — feeding makes plants outgrow the glass. Prune instead to keep the scene in proportion.
Common questions
Do closed and open terrariums really need different plants?
How often do I water a terrarium?
Why is my terrarium foggy?
Do terrariums need a drainage hole?
Can I use any jar or container?
How long does a terrarium last?
Pick your type first — closed for tropical plants, open for succulents — then build the layers in order and go easy on the water. A first terrarium costs very little, takes an afternoon, and can sit happily on a shelf for years.
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