Workshop Guide
Closed
Closed
Terrarium Guide
Build it. Seal it. Watch it thrive.
🌿 🫙 💧 🐸 🌱
What Makes It Closed
A little world inside a bottle
A closed terrarium is a sealed glass container that creates its own self-sustaining ecosystem. The plants inside breathe, transpire, and recycle moisture — fogging the glass at night and clearing by morning. It's basically a tiny rainforest on your shelf, and once it's balanced, it barely needs you at all.
Open Terrarium
Closed Terrarium ← you're here
Succulents & cacti
Tropical & moisture-loving plants
Water every 2–3 weeks
Water every 1–3 months (or less!)
Low humidity
High humidity — sealed in
Bright indirect light
Medium indirect light — no direct sun
Open top or wide opening
Lid, cork, or tight-fitting top
💡 If you see condensation on the glass each morning that clears by midday — your terrarium is perfectly balanced. That's the water cycle in action!
Your Kit
What's on your table
Before you start, look over everything at your station. Here's what you have — and why each piece matters.
Sealed Glass Container
With a lid or cork top — traps humidity inside
Pumice or Calcined Clay
Drainage layer — keeps roots from waterlogging
Sphagnum Moss
Separates soil from drainage — acts as a filter
Tropical Soil
Rich, moisture-retaining mix for tropical plants
Tropical Plant(s)
The living stars — ferns, fittonias, mosses
Living Moss
Covers the soil — stays lush in high humidity
Décor
Figurines, pebbles, stones — your finishing touch
The Layers
How the layers stack up
Every layer has a specific job inside a closed system. The order matters — don't skip or swap them.
Cross-section view — bottom to top
6
Personal style
5
Top layer
4
The stars ⭐
3
2–3" deep
2
½" layer
1
1–2" deep
💡 The sphagnum moss layer is what makes closed terrariums different. It acts as a natural barrier that keeps your soil from mixing down into the drainage layer — keeping everything clean and healthy long-term.
Let's Build It
Step-by-step build guide
Take your time with each step. A well-built closed terrarium can thrive for months — or even years — with almost no maintenance. It's worth doing carefully.
1
Clean your container
Wipe the inside of your glass with a clean, dry cloth. Any dust, fingerprints, or residue will be sealed inside permanently — so take a minute to get it clean now. This is the one step people skip and always wish they hadn't.
💡 Hold it up to the light and rotate it slowly to catch any spots you missed.
2
Add your drainage layer — pumice or calcined clay
Pour 1–2 inches of pumice or calcined clay into the bottom of your container. This layer stores any excess water below the root zone so your plants never sit in standing moisture. In a sealed system this is critical — there's no way for water to escape, so drainage has to do all the work.
💡 Tap the sides gently to level it out. A flat, even layer is your foundation.
3
Add your sphagnum moss barrier
Take a handful of sphagnum moss and spread it in a thin, even layer — about half an inch — on top of your drainage material. Press it down lightly so it creates a continuous barrier across the entire base. This is what keeps your soil from migrating down into the drainage layer over time.
⚠️ Don't pack it too tight — the moss barrier needs to let water pass through downward, while stopping soil particles from going with it.
4
Add your tropical soil
Scoop 2–3 inches of tropical soil on top of the moss barrier. Unlike succulent mix, tropical soil is designed to hold moisture — which is exactly what you want in a closed system. Pat it down gently and create a slightly mounded or tiered landscape if you'd like some visual depth.
🌿 Slightly varying the soil height creates a more natural, interesting landscape inside the glass.
5
Plant your tropical plants
Gently remove each plant from its pot and shake off any excess soil. Create planting holes, nestle the roots in, and firm the soil around the base. Start from the back and work forward, placing taller plants behind shorter ones. Give each one a little room — they will grow.
⚠️ Make sure no leaves are pressed against the glass walls. Leaves touching glass can rot when moisture condenses there.
6
Cover with living moss
Lay sheets or clumps of living moss over the exposed soil surface, pressing it down gently so it makes good contact with the soil. The living moss will establish itself and spread over time, creating a lush carpet-like ground cover. Cover as much bare soil as possible.
💡 Tuck the moss right up to the base of your plants and into any gaps. The more contact with the soil, the faster it roots and establishes.
7
Add your décor
Place your figurines, stones, or decorative elements wherever feels right. In a closed terrarium, décor looks best nestled into the moss or perched on small pebbles — anything that looks like it belongs on a tiny forest floor. Try a few arrangements before you seal it.
💡 Less is more in a closed terrarium — the plants and moss will fill in over time, so leave a little room for growth.
8
Water lightly, then seal
Before you close the lid, give your terrarium a light misting or a few small splashes of water — enough to dampen the soil but not saturate it. Then seal the lid and place it in medium indirect light. Watch over the next few days for the condensation cycle to establish.
💡 You'll know you've added the right amount of water when you see light condensation in the morning that clears by midday. Heavy fog all day = too wet, crack the lid. No condensation = too dry, add a small splash.
Care Guide
Keeping your terrarium thriving
Here's the beautiful thing about a well-built closed terrarium — it mostly takes care of itself. Once it finds its balance, your main job is just to watch it grow.
Watering
Every 1–3 months — or possibly never! Watch the condensation cycle. Only add water if the soil looks dry and you see no morning condensation.
Light
Medium indirect light only. Never place in direct sun — the sealed glass amplifies heat and will cook your plants. A few feet from a bright window is ideal.
Temperature
Comfortable between 60–80°F. Keep away from heating vents and cold drafts. Avoid windowsills in winter — cold glass causes condensation overload.
Pruning
Trim yellowing leaves or plants that grow too large with small scissors. Remove dead material promptly — in a sealed system, decay spreads quickly.
Quick reference by common tropical plant
| Plant | Light | Humidity Need | Growth |
|---|---|---|---|
| Fittonia | Low–medium indirect | High | Moderate, spreading |
| Fern (various) | Medium indirect | High | Moderate to fast |
| Peperomia | Low–medium indirect | Medium | Slow, compact |
| Selaginella | Low–medium indirect | High | Fast, spreading |
| Mini Pilea | Medium indirect | Medium | Slow to moderate |
| Baby Tears | Medium indirect | High | Fast, ground cover |
💡 When choosing plants, pick ones with similar humidity and light needs. A closed terrarium is a shared environment — one plant that hates humidity will struggle while the others thrive.
Reading Your Terrarium
What the condensation is telling you
The foggy glass isn't a problem — it's your terrarium communicating. Here's how to read it.
Light condensation in morning, clear by midday
Perfect balance. Do nothing.
Heavy fog all day, water droplets streaming
Too much moisture. Crack the lid for 24–48 hours, then reseal.
Completely clear glass, dry soil visible
Too dry. Add a small amount of water — a tablespoon or a gentle misting is enough.
What You Learned
The bigger picture
You didn't just build a terrarium — you built a functioning miniature ecosystem. Here's the science behind what you made.
01
The water cycle in a jar
Your closed terrarium replicates Earth's water cycle in miniature. Water evaporates from the soil, condenses on the glass, and runs back down — endlessly recycling the same water without waste.
02
Layering creates a living system
Each layer has a specific ecological role. Drainage stores runoff. The sphagnum barrier filters. The soil feeds. The plants photosynthesize. The moss regulates humidity. Remove any layer and the system breaks down.
03
Plants breathe and so does your terrarium
During the day, your plants absorb CO₂ and release oxygen. At night, they release CO₂. In a sealed system this exchange is balanced — the plants create the air they need to survive.
04
Humidity is a resource, not a problem
In an open terrarium, moisture escapes and must be replaced. In a closed system, it's captured and reused. The plants that thrive here evolved in rainforests — places where humidity never leaves.
05
Balance over intervention
A well-built closed terrarium needs almost nothing from you once it's balanced. This is a lesson in designing systems that sustain themselves — rather than constantly patching problems from the outside.
06
Observation is a skill
Reading your terrarium's condensation teaches you to notice subtle changes. Is it foggier than yesterday? Clearer? This kind of attentive, unhurried observation is rare — and surprisingly calming to practice.
Troubleshooting
When something looks off
| What you're seeing | Likely cause | What to do |
|---|---|---|
| Heavy condensation all day, won't clear | Overwatered at the start | Crack the lid for 24–48 hrs until it balances, then reseal. |
| Yellowing or mushy leaves | Too much moisture / rot beginning | Remove affected leaves immediately. Crack lid to reduce humidity for a few days. |
| Leaves pressing against glass turning brown | Condensation contact rot | Trim those leaves. Reposition plants away from glass walls. |
| Soil looks dusty dry, no condensation | Not enough water at setup | Add a small amount of water — 1–2 tablespoons. Monitor over 24 hrs. |
| Plants stretching toward light | Not enough light | Move closer to a bright window — but never in direct sun. |
| Mold or white fuzz on soil | Too much moisture + poor airflow | Remove mold with a cotton swab. Crack lid for a few days. Reduce moisture level. |
| Plants growing too large, crowding | Happy plants! Just overgrown | Trim with small scissors. Remove one plant if needed to give others space. |
Seal it. Watch it. Let it grow.
You just built a self-sustaining world in a glass jar.
Give it time, give it light, and trust the process.
Medium indirect light · No direct sun · Read the condensation · Trim when needed
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