TERRAGLASS
Little worlds under glass — terrariums, moss, and miniature gardens.
From layering the substrate and sizing a jar to counting plants, tracking humidity, covering the floor in moss, and sizing the drainage layer, TerraGlass pairs free hands-on calculators with practical guides and a richly illustrated museum. Build a little world under glass, one layer at a time.
Terrarium Tools & Calculators
Free tools for building and maintaining a glass garden — substrate layer ratio, jar & vessel volume, plant count, humidity guide, moss coverage, and drainage layer calculators.
Substrate Layer Ratio Calculator
Get the drainage, charcoal, substrate, and top-dressing depths for a planted terrarium from your container's height and open/closed type
Jar & Vessel Volume Calculator
Find the total volume of a cylinder jar, glass globe, bell jar, or rectangular tank, plus a realistic usable-substrate estimate
Plant Count Calculator
See how many plants of a given mature spread fit your container's floor area at a sparse, moderate, or full planting density
Terrarium Humidity Guide
Get a target humidity range and a suggested misting cadence for moss & ferns or air plants, based on vessel type and room humidity
Moss Coverage Calculator
Work out how many moss pads or fragments you need to cover a floor, and how long a sparser fragmented planting takes to fill in
Drainage Layer Calculator
Work out how much LECA, gravel, or lava rock to buy for a terrarium's drainage layer, from floor area and substrate depth
Museum of Glass Gardens
Wander an illustrated collection — terrariums and bottle gardens, moss and ferns, air plants and epiphytes, and the vivariums and glasshouses that shaped the wider history of gardening under glass, each in its own gallery. Every entry, image, and fact is drawn from Wikipedia and Wikimedia Commons.
Tour the museum →From the Journal
Practical guides on layering a terrarium, choosing moss and ferns, keeping air plants happy, and picking the right jar — reading to pair with the calculators above.
How to Layer a Terrarium: Drainage, Substrate, and Moss
A practical walkthrough of the four-layer stack that makes a planted terrarium work — drainage, charcoal, substrate, and top dressing — and why the order matters.
Open vs Closed Terrariums: Which One Should You Build?
The practical differences between an open and a closed terrarium — humidity, watering, plant choice, and maintenance — and how to decide which suits your space.
Choosing the Right Moss for Your Terrarium
A guide to the mosses commonly used in terrariums — cushion moss, sheet moss, and java moss — and how their growth habits should shape your choice.
Ferns for Terrariums: The Best Varieties for Beginners
A rundown of beginner-friendly terrarium ferns — Boston fern, maidenhair fern, bird's nest fern, and table fern — and what makes each one suited to life under glass.
Air Plants 101: Caring for Tillandsia Without Soil
How Tillandsia air plants actually get their water and light without soil, and the watering, placement, and terrarium habits that keep them healthy.
How Much to Water a Closed Terrarium (and How Often)
Reading the signs of a well-balanced closed terrarium — condensation patterns, substrate moisture, and how to correct a jar that's too wet or too dry.
Keep Learning
Plain-language reference on the building blocks of a glass garden — terrarium basics, mosses and ferns, air plants and epiphytes, and the vivarium and glasshouse history behind it all.
Visit the Learn hub →