Build a Closed Terrarium Step‑by‑Step

• Understand what a closed terrarium is and why it’s ideal for beginners
• Learn how to choose the right glass container and humidity-loving plants
• Discover which materials are essential for drainage, moisture management, and aesthetics
• Step-by-step guidance on creating layers, arranging plants, and sealing your terrarium
• Master tips for positioning, lighting, and long-term maintenance

Introduction

A closed terrarium is a sealed glass container that houses moisture-loving plants and creates its own mini ecosystem. These low-maintenance indoor gardens recycle water, air, and nutrients within a self-contained microenvironment—making them ideal for growers of all experience levels.

Whether you want to bring a touch of greenery to your office, create a zen tabletop display, or give a thoughtful handmade gift, building a closed terrarium is a simple and rewarding project.

In this guide, we’ll walk you through every stage of the process—from selecting the perfect vessel and plants to maintaining a thriving miniature jungle. If you’re curious about the science behind these fascinating ecosystems, check out our in-depth guide to closed terrariums.

Preparing to Build: Choosing a Container and Materials

Terrarium Containers: What Works Best

A wide range of glass containers can serve as the foundation for your closed terrarium. Options include:

• Mason jars with lids
• Glass cookie jars or apothecary jars
• Repurposed candle jars or fishbowls with clear covers

The most important requirement is that the vessel be transparent and come with a tight-fitting lid or cover to trap humidity.

Ventilation Options

For beginners, we recommend starting with a completely sealed terrarium. This creates a stable humidity cycle. Semi-sealed containers require more frequent monitoring and aren’t as self-sustaining.

Best Plants for Closed Terrariums

Choose plants that thrive in high humidity and indirect light. Easy-care options include:

• Ferns (maidenhair, Boston)
• Fittonia (nerve plant)
• Mosses (sheet, cushion, mood moss)
• Peperomia varieties

Materials Checklist

Item	Purpose
Glass container with lid	Houses your terrarium and traps humidity
Pebbles or LECA	Creates drainage and prevents root rot
Activated charcoal	Filters air and water to reduce mold
Terrarium soil or coco coir	Supports plant roots and retains moisture
Humidity-loving plants	Survive well in a closed, moist environment
Decorative elements (rocks, bark, figurines)	Add personality and structure
Tweezers or chopsticks	Assist in placing plants and décor
Spray bottle	Evenly mists water without over-saturating

Cleaning the Vessel and Assembling Supplies

Start with a sterile container to prevent the growth of mold, algae, or bacteria.

How to Clean Your Glass Container

• Wash the container with warm, soapy water
• Rinse thoroughly with white vinegar to neutralize soap residue
• Dry completely using a clean, lint-free cloth

Set Up Your Workspace

Lay out all materials in the order you’ll use them—starting with pebbles and ending with plants and décor. This minimizes mess and allows you to work quickly once you start layering.

Layering: Drainage, Charcoal, and Substrate in Order

Step 1: Create a Drainage Layer

Add 1–2 inches of pebbles or LECA balls to the bottom of your container. This allows excess moisture to drain away from plant roots, preventing rot.

Step 2: Add Activated Charcoal

Sprinkle a thin layer of activated charcoal over the drainage base. This layer helps absorb odors and keeps the terrarium free from bacteria and toxins.

Step 3: Add Substrate

Carefully spoon in your terrarium-specific soil or a blend of coco coir and perlite. Aim for about 2–3 inches of depth. Slightly slope the substrate from back to front to create visual dimension and natural water channels.

Arranging Hardscape and Placing Plants Thoughtfully

Place Hardscape Before Plants

Install any large rocks, wood pieces, or background décor before you plant. Doing so avoids dislodging roots once placed.

Strategic Plant Placement

• Position taller plants toward the back or center
• Place lower, spreading mosses or groundcovers in front
• Use tweezers or chopsticks to gently firm soil around roots

Arrange plants in staggered heights to mimic a naturalistic setting and ensure good light distribution.

Adding Moss and Decorative Touches for Humidity Retention

Use Moss as a Living Mulch

Moss not only beautifies your terrarium, it also retains surface moisture. Cushion or sheet moss work best to cover any exposed soil.

Decorate with Intention

Add small stones, bark chips, or tiny figurines to reflect your personal style. Keep scale and balance in mind to avoid overcrowding.

Watering Carefully and Closing the Lid to Start the Cycle

Watering Tips

• Use a spray bottle to lightly mist the substrate after planting
• The medium should feel moist, not soggy
• Avoid standing water at the bottom layer

Seal the Environment

Close the lid tightly to begin the self-regulating water cycle. Over time, you’ll observe evaporated moisture forming on the glass, then condensing back into the soil—just like a miniature rain cycle.

Positioning the Terrarium in Appropriate Light Conditions

Lighting Needs

Closed terrariums thrive in bright, indirect light. Avoid direct sunlight, which can heat the container like a greenhouse and damage plants.

Best Locations

• Near east or north-facing windows
• On bookshelves or desks that get ambient daylight
• Under grow lights if no natural light is available

Ongoing Maintenance: Pruning, Airing Out, and Monitoring Moisture

What to Check Regularly

• Foggy glass: indicates high moisture—may need airing
• Dry soil: time to mist lightly
• Mold or foul odor: remove affected material and sanitize

Pruning and Airing

Trim overgrown plants with sterilized scissors. If excessive condensation builds up, briefly open the lid to let moisture escape, then reseal.

Monthly Maintenance Checklist

• Wipe down inner glass if heavily fogged
• Prune or remove dead leaves
• Mist lightly if soil appears dry
• Check for root rot or fungal growth

Conclusion: Enjoy Your Self-Contained Ecosystem

You’ve just created a thriving mini jungle in a jar—a beautiful and functional living decoration that largely takes care of itself. With the right setup and a watchful eye, a closed terrarium can last for years with minimal upkeep.

Terrariums are perfect for beginners due to their forgiving nature and stunning impact. Keep experimenting with plant combos, container types, or even layering techniques to take your terrarium game to the next level.

Feeling inspired? Explore our full guide to learn more about the science and art behind these joyful ecosystems: Read our in-depth terrarium guide.