Table of Contents

What Is Terrariums?

A terrarium is a miniature garden enclosed (or partially enclosed) in a transparent container — typically glass — that creates a small, self-sustaining ecosystem. Plants grow inside, moisture cycles through evaporation and condensation, and the result is a little world under glass that requires minimal care.

The concept is beautifully simple: take a glass container, add drainage material, soil, and plants, and you’ve got a living decoration that practically takes care of itself. The most famous terrarium in the world — David Latimer’s sealed bottle garden — was last watered in 1972 and is still growing just fine.

Two Types

Closed Terrariums

Fully sealed or nearly sealed containers that create their own water cycle. Water evaporates from soil and plant surfaces, condenses on the glass, and drips back down — recycling indefinitely. Closed terrariums are essentially tiny tropical rainforests: warm, humid, and self-regulating.

Best for: tropical plants, ferns, mosses, fittonias, and other humidity-loving species.

Open Terrariums

Containers without lids or with wide openings that allow air circulation. Moisture escapes, so these need occasional watering. Open terrariums work well for plants that prefer drier conditions.

Best for: succulents, cacti, air plants, and other drought-tolerant species.

How to Build One

Materials Needed

• A glass container (jar, bowl, bottle, or purpose-built terrarium)
• Small stones or pebbles for drainage
• Activated charcoal (absorbs odors and prevents bacterial growth)
• Potting soil appropriate for your plant choices
• Plants
• Optional: decorative elements (stones, figures, driftwood)

The Process

1. Drainage layer — Add 1-2 inches of pebbles or gravel at the bottom. There’s no drainage hole, so this layer prevents roots from sitting in standing water.

2. Charcoal layer — A thin layer of activated charcoal on top of the drainage material. This keeps the ecosystem fresh by filtering the water.

3. Soil — Add 2-3 inches of potting mix. Use soil appropriate for your plants — standard potting mix for tropical plants, cactus/succulent mix for open terrariums.

4. Plants — Dig small holes, place your plants, and press soil gently around the roots. Start with larger plants first, then fill in with smaller ones and ground cover like moss.

5. Decoration — Add stones, driftwood, or small figurines for visual interest.

6. Water — Mist lightly (don’t soak) and seal the lid for closed terrariums. For open ones, water sparingly as needed.

The Science

A closed terrarium is a miniature demonstration of the water cycle and carbon cycle in action:

Water cycle — Water evaporates from soil and transpires from plant leaves, condenses on the glass, and returns to the soil. The system recycles the same water indefinitely.

Carbon cycle — Plants photosynthesize during the day (absorbing CO2, releasing oxygen) and respire at night (absorbing oxygen, releasing CO2). Decomposing organic matter releases nutrients back into the soil. The system reaches a rough equilibrium.

Energy input — The only thing a closed terrarium needs from the outside world is light. Sunlight powers photosynthesis, which drives everything else. (Direct sunlight will overheat a sealed container, though — bright indirect light is ideal.)

A Brief History

The terrarium was invented accidentally in 1842 by Dr. Nathaniel Bagshaw Ward, a London physician and amateur botanist. He’d placed a moth chrysalis in a sealed glass jar with soil. Before the moth emerged, he noticed ferns and grass sprouting in the jar — thriving in the enclosed environment despite London’s polluted air.

Ward realized that sealed glass containers could protect plants from air pollution and maintain consistent humidity. His “Wardian cases” (as they became known) revolutionized the transport of live plants across oceans. Previously, most plants died during long sea voyages. Wardian cases enabled the mass transport of tea plants to India, rubber plants to Malaysia, and countless botanical specimens to gardens worldwide. They changed global agriculture.

Why People Love Them

Terrariums have experienced a major resurgence in popularity:

• Low maintenance — Closed terrariums need almost no care. Perfect for people who kill houseplants.
• Small space friendly — A terrarium fits on a desk, windowsill, or shelf.
• Creative expression — Building a terrarium is a genuinely enjoyable craft project. The design possibilities are endless.
• Connection to nature — A tiny green world on your desk provides a surprising amount of psychological comfort.
• Educational — Terrariums demonstrate ecological principles in a visible, tangible way. They’re excellent teaching tools for children.

The hobby has a vibrant online community. Social media platforms are full of terrarium builds, time-lapses of plant growth, and creative container choices — everything from old light bulbs to vintage apothecary jars to elaborate custom-built display cases. The barrier to entry is low (your first terrarium can cost under $20) and the satisfaction of watching a tiny ecosystem thrive is genuinely rewarding.

Frequently Asked Questions

How often do you need to water a closed terrarium?

Rarely — that's the beauty of it. A properly sealed closed terrarium creates its own water cycle. Water evaporates from the soil and plants, condenses on the glass, and drips back down. Many closed terrariums only need watering every few months, or even less. If you see heavy condensation, open the lid briefly to let excess moisture escape.

What plants work best in terrariums?

For closed terrariums: ferns (maidenhair, button fern), mosses, fittonias (nerve plants), peperomias, and small tropical plants that love humidity. For open terrariums: succulents, air plants, cacti, and other plants that prefer drier conditions. The key is matching plants to the terrarium type — humidity-loving plants in closed, drought-tolerant in open.

How long can a terrarium last?

Indefinitely, if maintained. David Latimer's closed bottle terrarium, planted in 1960, is still thriving after 60+ years — it was last watered in 1972. The self-sustaining water and nutrient cycles can keep a closed terrarium going for decades. Open terrariums require more attention but can also last for years with basic care.

Further Reading

• Terrariums - Smithsonian Gardens
• Indoor Gardening - University of Missouri Extension
• Plant Science - Royal Horticultural Society