Coir fibre
Four parts. The skeleton of the mix — holds structure for years and refuses to compact under its own weight.
Vitrine Quarterly — Issue 12 — Sealed Systems
Everything a world needs,
stacked in eight inches of glass.
A field journal for people who build closed ecologies on windowsills. We read the vessel the way a geologist reads a cliff face: from the rim down, one seam at a time.
Layer 01 · 012 mm
Moss mat
The living lid
Nothing here is decoration. The moss mat is the terrarium's lung and its clock — the first thing to tell you the humidity has slipped, weeks before a fern will admit it.
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Cushion moss stops drinking
Day 61. Leucobryum tips pale to silver-grey by mid-afternoon and recover by dawn. Normal. Panic only if the recovery takes two nights.
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First unassisted sporophyte
Day 76. A single seta pushed up beside the driftwood. Sealed systems rarely reproduce this early; we credit the north window and total neglect.
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Springtails colonise the north slope
Day 90. Population estimated at 400. They are the cleanup crew, the mould insurance, and the only livestock that will forgive you.
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Condensation line stabilises
Day 115. Fog now clears from the glass by 10:00 daily. This is the signal that the vessel has finished arguing with itself.
Sealed
Bryophyte
North light
No misting
Layer 02 · 038 mm
Loam & leaf mould
Where the roots negotiate
Twenty-six millimetres of substrate is the whole economy. Too rich and it sours; too lean and the ferns stall. Our house mix, weighed dry, in four parts.
Leaf mould
Three parts, beech preferred, two winters old. Slow nitrogen and a native fungal culture you cannot buy.
Pumice, 3 mm
Two parts. Air pockets that survive watering. The difference between damp soil and drowned soil.
Worm cast
One part, no more. Enough to feed a sealed system for three years without inviting algae to the glass.
Layer 03 · 074 mm
Horticultural charcoal
The filter nobody sees
A black seam two centimetres thick, doing the unglamorous work of adsorbing everything the soil above releases. Twelve vessels, measured at day 400.
| Vessel | Seam | Substrate | Clarity at d400 |
|---|---|---|---|
| Ash cloche | 22 mm | Coir / mould | 98% |
| Kilner No. 4 | 18 mm | Coir / pumice | 94% |
| Wardian box | 25 mm | Leaf mould | 96% |
| Demijohn | 8 mm | Peat-free | 71% |
| Bell jar (control) | 0 mm | Coir / mould | 44% |
Clarity measured as unobstructed glass area, photographed at 10:00 under identical north light.
Layer 04 · 096 mm
Silica seam
“A terrarium is not a garden. It is an argument between water and glass that you have agreed to referee for the rest of your life.”
Layer 05 · 124 mm
Drainage course
Coarse, loose, and load-bearing
Thirty-six millimetres of washed grit — the void that decides whether the whole column survives a heavy hand with the watering can. Get letters from the layer below.