Terrarium Open Or Closed: Your Ultimate Guide To Choosing The Perfect

Written ByHoward Parker

So, you’re standing there with a beautiful glass jar, a bag of soil, and a collection of tiny, adorable plants. You’re ready to create your own miniature green world, but one big question is stopping you in your tracks: should you build a terrarium open or closed?

It’s a classic dilemma, and the choice you make will define everything about your new ecosystem, from the plants you can grow to the care it needs. Don’t worry—you’ve come to the right place. As someone who has built (and occasionally failed with) dozens of these little worlds, I’m here to be your guide.

I promise that by the end of this article, you’ll not only understand the fundamental differences but also feel confident in choosing the perfect setup for your home and lifestyle.

We’ll dive deep into the unique benefits of each type, explore the best plants for both open and closed environments, and even troubleshoot some common problems. Let’s get started and build something beautiful together!

Understanding the Core Difference: The Lid is Everything

At its heart, the decision between a terrarium open or closed comes down to one simple thing: a lid. This single component completely changes the environment inside your glass container, creating two distinctly different types of ecosystems.

Think of it like this: a closed terrarium is a tiny, self-contained rainforest, while an open terrarium is more like a miniature arid garden. The presence or absence of a lid dictates airflow, humidity, and water retention, which in turn determines which plants will thrive.

What is a Closed Terrarium?

A closed terrarium has a lid or a seal that traps moisture inside. As water evaporates from the soil and plants (a process called transpiration), it condenses on the glass walls and drips back down, creating a self-watering cycle. This results in a high-humidity environment that requires very little outside intervention.

What is an Open Terrarium?

An open terrarium, as the name suggests, has no lid. This allows for constant airflow and lets moisture escape freely. The environment inside is much drier and closer to the ambient conditions of your room, making it ideal for plants that prefer arid, desert-like conditions.

The Case for Closed Terrariums: A Self-Sustaining Miniature World

There’s something magical about a closed terrarium. It’s a nearly self-sufficient ecosystem you can set on a shelf and watch flourish with minimal effort. Here’s a closer look at the benefits of terrarium open or closed systems, focusing on the sealed variety.

Key Benefits of a Closed Terrarium:

  • Low Maintenance: Once established, a balanced closed terrarium can go for weeks or even months without watering. It creates its own rain cycle! This is perfect for busy plant parents or those who tend to forget watering day.
  • Thriving Humidity-Lovers: Tropical plants that crave high humidity, like ferns, mosses, and Fittonia, absolutely adore the steamy conditions inside a sealed jar. They’ll grow more lush and vibrant than they ever could on an open windowsill.
  • A Fascinating Ecosystem: Watching the water cycle in action—condensation on the glass, “rain” dripping down—is a captivating and educational experience. It’s a living science experiment right in your home.

The Ideal Plants for a Closed System:

To succeed, you need plants that love moisture and humidity. Dry-loving succulents are a definite no-go here!

  1. Ferns: Maidenhair Fern, Bird’s Nest Fern, and Button Fern are fantastic choices.
  2. Mosses: Cushion Moss, Sheet Moss, and Mood Moss create a lush, green carpet.
  3. Nerve Plants (Fittonia): Their colorful, veined leaves add a stunning pop of color.
  4. Baby Tears (Soleirolia soleirolii): A delicate, fast-spreading ground cover.
  5. Creeping Fig (Ficus pumila): A lovely vining plant that will happily climb the walls of your terrarium.

Embracing the Open Terrarium: A Breath of Fresh Air for Your Plants

If you’re drawn to the stark beauty of succulents, cacti, and air plants, then an open terrarium is your perfect match. These systems are all about excellent airflow and dry conditions, preventing the root rot that plagues these plants in humid environments.

Key Benefits of an Open Terrarium:

  • Perfect for Arid Plants: This is the only way to successfully keep succulents, cacti, and other desert dwellers in a terrarium. A closed system would be a death sentence for them.
  • Zero Risk of Mold: The constant airflow means you won’t have to worry about mold or mildew, a common issue in overly wet closed terrariums.
  • More Design Flexibility: You can create stunning, desert-inspired landscapes using different colored sands, rocks, and sculptural plants that wouldn’t survive in a humid, sealed jar.

The Ideal Plants for an Open System:

Think dry, sunny, and airy. These plants hate having “wet feet” and need their soil to dry out between waterings.

  1. Succulents: Echeveria, Haworthia, Gasteria, and Sedum varieties are all great candidates.
  2. Cacti: Small species like Thimble Cactus or Star Cactus work well, but be mindful of their spines!
  3. Air Plants (Tillandsia): These don’t even need soil! You can simply nestle them on top of sand or amongst rocks. Just be sure to take them out for a soak every week or two.
  4. String of Pearls/Turtles/Hearts: These trailing succulents look incredible spilling over the edge of an open bowl.

Your Terrarium Open or Closed Guide: Matching Plants to a System

This is where many beginners go wrong. You can’t just put any plant in any jar. The most critical part of this terrarium open or closed guide is understanding that you must choose your system based on the plants you want to grow, or vice-versa.

The Golden Rule of Terrarium Building:

Never mix plant types! Don’t put a moisture-loving fern next to a desert-loving succulent. One of them will inevitably suffer and die. Your terrarium should be a community of plants with similar light, water, and humidity needs.

Here’s a simple cheat sheet to help you decide:

Choose a CLOSED terrarium if you love:

  • Lush, green, jungle-like aesthetics.
  • The idea of a low-maintenance, self-watering system.
  • Plants like ferns, mosses, fittonia, and peperomia.

Choose an OPEN terrarium if you love:

  • Minimalist, desert-inspired designs.
  • Hands-on watering and care routines.
  • Plants like succulents, cacti, and air plants.

Common Problems with Terrarium Open or Closed Setups (And How to Fix Them!)

Even with the best intentions, things can sometimes go sideways. Don’t be discouraged! Here are some common problems with terrarium open or closed systems and some pro tips on how to fix them.

For Closed Terrariums:

  • Problem: Mold or Fungus. This is almost always caused by too much water. The air is stagnant and overly damp.

    Solution: Take the lid off for a few hours each day to let it air out. You can also introduce springtails, tiny insects that are a natural cleanup crew and will eat mold for breakfast.
  • Problem: Foggy Glass All the Time. A little condensation is normal, but if you can never see your plants, it’s too wet.

    Solution: Same as above—remove the lid to allow some moisture to escape. A healthy cycle involves condensation in the morning/evening that clears up during the day.
  • Problem: Leggy, Stretched-Out Plants. This means your terrarium isn’t getting enough light.

    Solution: Move it to a spot with brighter, indirect sunlight. Direct sun can cook the plants inside a sealed glass jar!

For Open Terrariums:

  • Problem: Mushy, Rotting Plants. You’re overwatering! Remember, these are arid plants.

    Solution: Water less frequently and more precisely. Use a squirt bottle or pipette to direct water at the base of the plants, avoiding the leaves. Ensure your soil is very well-draining.
  • Problem: Shriveling or Crispy Leaves. This is a sign of underwatering.

    Solution: While they like to be dry, they don’t want to be bone-dry forever. Give them a good drink, letting the soil dry out completely before watering again.
  • Problem: Pests like Mealybugs or Gnats.

    Solution: Isolate the terrarium immediately. You can dab mealybugs with a cotton swab dipped in rubbing alcohol. For gnats, let the soil dry out more between waterings, as they lay eggs in damp soil.

Building a Sustainable Terrarium: Eco-Friendly Best Practices

One of the best parts of building a terrarium is creating a slice of nature. You can enhance this by making it an eco-friendly terrarium open or closed project from the start.

A truly sustainable terrarium open or closed system is about mindful sourcing and long-term health.

  • Upcycle Your Container: You don’t need a fancy, store-bought vessel. Old pickle jars, coffee pots, or glass vases make fantastic and unique terrariums.
  • Forage Responsibly: If you collect moss or stones from the outdoors, do so sustainably. Never take more than a small amount from any single area, and be sure you have permission.
  • Use Peat-Free Soil: Peat moss harvesting is damaging to fragile bog ecosystems. Look for coconut coir-based potting mixes as a more sustainable alternative.
  • Create a Bioactive Setup: For closed terrariums, introduce beneficial microfauna like springtails and isopods. They act as a natural cleanup crew, breaking down waste and preventing mold, creating a truly self-sustaining ecosystem.

Frequently Asked Questions About Terrarium Open or Closed Systems

Do open terrariums need drainage?

Yes, absolutely! This is one of the most important terrarium open or closed best practices. Since there’s no drainage hole, you must create a false drainage layer at the bottom using gravel, LECA, or pebbles. This gives excess water a place to go so it doesn’t rot your plants’ roots.

How often do you water a closed terrarium?

Very rarely! A well-balanced closed terrarium might only need a light misting every few months, if at all. The key is to watch for condensation. If you see a light fog on the glass in the morning that clears by afternoon, it’s perfect. If it’s always dry, add a few spritzes of water. If it’s always foggy, air it out.

Can I put a lid on my succulent terrarium?

Please don’t! This is a recipe for disaster. Succulents and cacti need dry air and low humidity. Trapping them in a sealed container will lead to fast and fatal root rot. Always keep succulent arrangements in open containers.

What is the best light for a terrarium?

Bright, indirect light is the sweet spot for almost all terrariums. A spot near an east-facing window is often perfect. Direct southern or western sun can get too hot, especially for closed terrariums, effectively turning them into a greenhouse oven.

Your Terrarium Journey Begins Now

The debate over a terrarium open or closed isn’t about which one is “better”—it’s about which one is better for you and the plants you dream of growing. Both offer a unique and rewarding way to bring a touch of nature indoors.

By understanding the fundamental needs of your chosen plants and matching them to the right environment, you’re setting yourself up for success. Remember the golden rule: humidity-lovers go in a closed world, and desert-dwellers get a breath of fresh air in an open one.

So, take another look at that glass jar and those tiny plants. You now have the knowledge and confidence to make the right choice. Go forth, get your hands dirty, and create a beautiful, thriving miniature world. Happy building!

Howard Parker
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