Open vs Closed Terrariums: Which is Right for You?

What is the difference between open and closed terrariums? Closed terrariums are sealed glass containers that create self-sustaining humid environments for tropical plants like ferns and moss. Open terrariums have no lid, suit succulents and cacti that prefer dry conditions, and require regular watering.

Choosing between an open and closed terrarium isn't just aesthetic—it determines which plants you can grow, how much maintenance you'll do, and what kind of ecosystem you'll create. Understanding the fundamental differences helps you pick the right type for your space, lifestyle, and the plants you love.

The Fundamental Difference: Humidity

The presence or absence of a lid creates entirely different environments. A closed terrarium traps moisture, creating 70-90% humidity—similar to a tropical forest floor. An open terrarium has ambient room humidity, typically 30-50% in most homes.

This single factor—humidity—determines everything else about your terrarium:

Closed Terrariums: Self-Sustaining Ecosystems

A sealed terrarium creates its own water cycle. Plants transpire moisture, it condenses on the glass, and droplets return to the soil. This cycle can continue indefinitely without you adding water.

Best plants for closed terrariums:

• Fittonia (nerve plant)—colorful, forgiving, loves humidity
• Moss—multiple varieties, indicates moisture levels
• Miniature ferns—Maidenhair, Button fern
• Selaginella—native to India, feathery texture
• Peperomia—compact varieties, interesting foliage
• Pilea—aluminum plant, easy care

The main challenge with closed terrariums is achieving initial balance. Too much water leads to mold; too little and plants dry out. But once balanced, they're remarkably self-sufficient.

Open Terrariums: Desert in Glass

Without a lid, moisture evaporates freely. This suits plants adapted to arid conditions—succulents, cacti, and air plants that would rot in the humidity of a closed system.

Best plants for open terrariums:

• Echeveria—rosette succulents, many colors
• Haworthia—compact, low light tolerant
• Sedum—trailing varieties, interesting textures
• Small cacti—avoid fast-growing species
• Air plants (Tillandsia)—no soil needed
• Lithops—"living stones," conversation pieces

Open terrariums require regular attention. You'll water weekly (or as soil dries), monitor for pests, and occasionally rotate for even light exposure. They're more work but offer different creative possibilities.

Which Type Suits Your Lifestyle?

Consider your habits honestly:

Choose closed if you:

• Travel frequently or work long hours
• Tend to forget watering
• Want a "set and forget" living decoration
• Love ferns, moss, and tropical aesthetics
• Have lower light conditions

Choose open if you:

• Enjoy regular plant care as a ritual
• Have bright, direct sunlight available
• Prefer succulents and desert aesthetics
• Want to easily rearrange and modify
• Live in a very dry climate (closed terrariums can struggle)

Common Mistakes to Avoid

The biggest error is putting wrong plants in the wrong environment:

"Succulents in closed terrariums are the most common mistake we see. They rot within weeks. The humidity that ferns love is lethal to desert plants."

Other mistakes:

• Mixing plant types: Don't combine succulents and tropical plants—their needs are incompatible
• Overcrowding: Plants grow; leave room for expansion
• Wrong container: Closed terrariums need airtight seals; open terrariums need good drainage
• Direct sunlight on closed: Glass magnifies heat, cooking plants

Making Your Choice

There's no objectively better option—only what's better for you. If you're new to terrariums and want forgiveness, closed systems are more tolerant of neglect. If you want variety and don't mind regular care, open terrariums offer more plant options.

Many enthusiasts eventually have both types, appreciating the different rhythms each brings. A closed terrarium on your desk at work, thriving while you focus elsewhere. An open terrarium at home, a weekly ritual of watering and attention.

The best terrarium is the one that matches your life and brings you joy to observe.