A well-built terrarium is one of the lowest-maintenance ways to keep greenery at home — a self-contained little ecosystem in glass that needs watering every few weeks instead of every few days. It's also one of the most common questions we get from first-time plant owners: how do you actually build one, and which plants survive inside a closed jar? Here's a practical, no-fuss guide.
Open vs. Closed Terrariums
The first decision is the container itself, because it determines which plants will actually survive inside it.
- Closed terrariums (a jar or container with a lid) create a humid, self-watering micro-climate through condensation. They suit moisture-loving plants like ferns, moss, and fittonia, and can go weeks between waterings.
- Open terrariums (a bowl or open glass vessel) suit drier-loving plants like succulents and haworthia, which would rot in a closed, humid environment. They need slightly more frequent watering than closed ones, but far less than a normal potted plant.
Get this choice right and most of the ongoing care takes care of itself.
What You'll Need
- A clear glass container — a jar, fish bowl, geometric terrarium, or any vessel with reasonable depth
- A drainage layer of small stones or decorative pebbles
- A thin layer of activated charcoal (keeps the water from turning stagnant and smelly)
- A well-draining potting mix suited to your plant choice
- Small, slow-growing plants sized for the container
- Optional: moss, small figurines, or coloured stones for styling
How to Build a Terrarium, Step by Step
- Layer the base. Add roughly a 1–2 inch layer of pebbles for drainage, followed by a thin layer of activated charcoal.
- Add potting mix. A layer deep enough for your plants' root systems — usually 2–3 inches.
- Plant with care. Use a spoon or chopstick to dig small holes and place your plants, working from the back of the container forward so nothing gets crushed.
- Style it. Add moss around the base of the plants, and any decorative stones or figurines you like.
- Water lightly. Just enough to settle the soil — terrariums are very easy to overwater, especially closed ones.
Best Low-Maintenance Plants for Terrariums
For open terrariums, small succulents and haworthia are ideal — they tolerate the drier, airier environment and won't rot. For closed terrariums, look for moisture-loving, slow-growing plants like ferns, moss, and fittonia, which will happily use the humidity a sealed container creates.
Ongoing Care
- Light: Bright, indirect light. Direct sun through glass can cook the plants inside — terrariums act a little like a greenhouse.
- Watering: Closed terrariums may only need water every 3–4 weeks; open ones every 1–2 weeks. Always check the soil first — when in doubt, wait.
- Condensation: Light misting on the glass in a closed terrarium is normal and a good sign. If the glass is constantly fogged solid, crack the lid open for a day to let it breathe.
- Mould: A little white fuzz occasionally appears on soil or wood — it's usually harmless, but if it spreads, increase airflow and cut back on watering.
Frequently Asked Questions
Do terrariums need direct sunlight? No — bright, indirect light is best. Direct sun can overheat a closed terrariums glass.
How often should I water a terrarium? Far less than a regular potted plant. Closed terrariums can go 3–4 weeks; open ones need checking every week or two.
Are terrariums good gifts? Yes — they're compact, low-maintenance, and need very little instruction, which makes them one of our most popular gifting picks.
Can I add more plants later? Yes, as long as there's room and the new plant suits the same open or closed environment as the rest.
Ready to start one of your own? Browse our Terrariums collection for containers, plants, and the decorative pebbles you'll need to build it.