How to Make a Terrarium Step by Step (Open or Closed)

A terrarium is a tiny garden inside a glass container: a miniature green world that sits on a table and, once set up properly, almost takes care of itself. It's one of the prettiest projects for getting started with plants, and you need very few materials. Here's the complete guide to building yours step by step.

Open or closed terrarium: which to choose

The first decision is the type, because it determines both the plants and the care:

• Closed: a container with a lid. It recreates a humid, nearly self-sufficient environment, ideal for moss, ferns and small tropical plants. You water it very rarely.
• Open: no lid, with more airflow. Perfect for cacti, succulents and plants that hate excess humidity. It needs occasional watering.

If you're unsure, start with a closed one filled with jungle plants: they're the most spectacular and the best at holding humidity.

What you'll need

• A clear glass container (a jar, a fishbowl, a bottle).
• Gravel or expanded clay for drainage.
• Activated charcoal (keeps the water from going stale and smelling).
• Potting mix suited to your plants.
• Small plants and, if you like, moss.
• Optional decoration: stones, twigs or bark.

The ideal plants for a closed terrarium

Look for small, slow-growing, humidity-loving species:

• Fittonia: the queen of the terrarium, with its white or pink veins. To get to know it better, read our fittonia care guide.
• Dwarf ferns and moss, which carpet the floor in green.
• Ivy seedlings or small pilea.

Avoid putting succulents or cacti in a closed terrarium: the trapped humidity rots them within weeks.

Step-by-step assembly

1. Drainage layer: add 1-1.5 inches of gravel or expanded clay to the bottom. Since the container has no holes, this layer collects excess water and keeps the roots from sitting in it.
2. Charcoal layer: sprinkle a thin layer of activated charcoal over the gravel.
3. Potting mix: add a generous layer (2-3 inches) of soil, sloped slightly if you want to create visual depth.
4. Plant: scoop a hole with a spoon, set each plant in and firm the soil around the roots. Start with the biggest plants at the back.
5. Moss and decoration: cover the gaps with moss and add stones or twigs to taste.
6. First watering: mist with water until the soil is damp but not soggy. Wipe the glass with a paper towel to remove any soil splashes.

How to care for it afterward

The secret to a terrarium is not overwatering. The beauty of a closed one is that it recycles its own water: vapor condenses on the walls and falls back down.

• Watering: in a closed one, a light misting every few weeks is usually enough. In an open one, water when the soil dries out.
• Light: plenty of indirect light, never direct sun. The glass acts like a magnifying lens and would cook the plants.
• Airflow: if you see too much condensation or mold appears, take the lid off for a few hours.
• Maintenance: trim back anything that grows too much and remove dead leaves to keep the balance.

Common problems

• Walls always fogged up: too much humidity. Take the lid off for a few hours a day until it balances out.
• White or gray mold: too much water and too little airflow; remove the affected part and ventilate.
• Leggy, stretched plants: not enough light; move it closer to a bright window without direct sun.
• Yellow leaves: usually overwatering. If you're not sure what's wrong, try our AI diagnosis with a photo.

A project that lasts for years

A well-built, well-placed terrarium can live for years with minimal maintenance. It's the perfect way to bring greenery to a desk, a shelf or a bright bathroom. Start simple, watch how your little ecosystem evolves, and add details over time. You'll be amazed how little it asks for in return for how much it gives.