How to set up a glass terrarium: layers, then water
Updated: 21 October 2026
You already have the jar or the house on the table, and the question is what goes in first. A glass terrarium fails in two ordinary ways: a pond poured into a soldered frame, or succulents sealed under a lid that holds the humidity they rot in. This page is the layer order and the first watering. The containers are on the [glass terrarium comparison](/hub/houseplants/glass-terrarium). Peter F. used the Royal Horticultural Society, Kew and BBC Gardeners’ World for the method. No one here planted a test jar in a lab. A qualifying purchase can earn us a commission at no extra cost to you.
You already have the jar or the house on the table, and the question is what goes in first.
You already have the jar or the house on the table, and the question is what goes in first. A glass terrarium fails in two ordinary ways: a pond poured into a soldered frame, or succulents sealed under a lid that holds the humidity they rot in. This page is the layer order and the first watering. The containers are on the glass terrarium comparison. Peter F. used the Royal Horticultural Society, Kew and BBC Gardeners’ World for the method. No one here planted a test jar in a lab. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Closure | Stated size | Water note | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  ZOOBAYA ZOOBAYA greenhouse | Lift-off hinged top | 24.6 × 13.5 × 21.8 cm | UK reviews say it is not watertight | 7.4 | about £32.93 | View offer |
| Best value |  PYEF CRAFTS PYEF CRAFTS terrarium kit | Lid type not stated | 11 × 11 × 20 cm | Soil, moss, charcoal and stones in the kit | 7.7 | about £24.99 | View offer |
 Homtone Homtone house (23 cm) | Swing lid, can be propped | 23 × 14 × 18.5 cm | No watertight claim; slight leak in reviews | 8.1 | about £29.95 | View offer |
On this page
Clean glass, then the layers
Wash the glass with warm water and let it dry before anything organic goes in. The Royal Horticultural Society sets drainage as washed gravel or clay pebbles, then peat-free compost mixed with horticultural grit at about four parts compost to one part grit. Kew uses pebbles about 2–3 cm deep and a scatter of activated charcoal between the stones and the compost. A 5–7 cm compost bed will not fit an 11 cm house or a 1 litre kit jar. If you bought the PYEF kit, the soil, moss, charcoal, stones and tools are in the box and the plants are not. Ignore the 0.75 g weight field. When Kew and the RHS conflict, use the 4:1 peat-free blend.
Plants and the lid you will actually use
Put the largest plant in first, away from the glass. The RHS closed list is small ferns, fittonia, peperomia and moss. Succulents and cacti belong in a container you leave open. A Homtone swing lid is stated at 12 × 9 cm, so bare-root the plug before you try the door. Moss should come from your own garden, with insects shaken out, or from a shop. The Wildlife and Countryside Act 1981 restricts uprooting wild plants, and the RHS says not to take countryside moss without the landowner’s permission. Close the lid only when the plants match a humid climate. That choice is on closed or open terrarium. Succulents are on the succulent glass terrarium page.
First watering and condensation
Mist until the compost is damp, not until water sits on the gravel. Kew’s rule is plain: fog means too wet, so take the lid off for a few hours. BBC Gardeners’ World’s rule of thumb is that condensation on about a third of the glass can stay, heavier fog should be aired, and almost none means a small drink. Summer sun on the glass cooks a closed jar. A light mist in a sealed jar may mean water only a few times a year. Self-sustaining on a kit title is not a guarantee. If the compost smells sour after you have aired the jar, stop adding water. A cut from broken glass is a different call: report it through Citizens Advice in England and Wales, Advice Direct Scotland, or a Northern Ireland council.
When the house is not a vase
Soldered houses in this set draw leak complaints once people water them like bowls. Homtone reviews mention a slight leak. Both ZOOBAYA houses are described as letting water onto a shelf. LIMOR’s drain hole leaves water in the drip tray. If a bead appears at a seam, stop. Put a tray under the house and do not build a reservoir for the winter. If your hand does not fit, use bamboo tongs, a long spoon or chopsticks. The PYEF kit includes tongs. Do not force a nursery pot through a 12 × 9 cm flap.
Common questions
How deep should the gravel be in a small house?
Kew suggests about 2–3 cm of pebbles in a jar with room. That is a rule of thumb, not a standard, and it is already a lot inside LIMOR’s 12.4 cm height or a 1 litre kit jar. Use a thinner stone layer and only enough compost to cover the roots. A shop guide that wants 5–7 cm of soil plus a full gravel bed will bury the plants in an 11 cm house. Shrink both layers.
When do I close the lid?
Close it when the plants are the humid sort — small ferns, fittonia, peperomia, moss — and the compost is damp rather than flooded. Leave it open, or propped, for succulents and cacti. If you are not sure which you planted, leave the lid ajar for the first week and watch the glass. Sealing a mixed title on day one is the mistake this setup is trying to avoid.
Can I use moss from the garden?
Yes, if it is your garden. Shake out insects before it goes into a closed jar. Do not take moss from the countryside unless you have the landowner’s permission, which is the Royal Horticultural Society line, alongside the Wildlife and Countryside Act limits on uprooting wild plants. Bought moss, or the moss in a kit, avoids that problem. Protected sphagnum is not a craft harvest.
What if water comes out of the seams?
Stop pouring. Wipe the shelf, put a tray underneath, and let the compost dry back. Homtone, both ZOOBAYA houses and the LIMOR are described in UK reviews as leaking when people water generously. A soldered frame is not a vase. Later waterings should be a mist you can see disappear, not a reservoir you hope the joints will hold.
Which tools if my hand does not fit?
Use bamboo tongs, a long spoon or chopsticks, which is how narrow bottle gardens are planted. The PYEF kit includes tongs. A 12 × 9 cm swing lid, as on the Homtone, will not take a hand and a nursery pot together. Bare-root the plug before you try the door. Forcing a pot is how the glass cracks, and cracked glass is a return, not a planting technique.
Related pages
Sources
Public UK sources named below. amazon.co.uk prices, stars and review counts on these eight listings were read for this comparison. Page updated 21 October 2026.
- RHS, Terrariums and bottle gardens (retrieved 21.10.2026)
- BBC Gardeners’ World, terrarium care (retrieved 21.10.2026)
- Kew, Make your own terrarium (retrieved 21.10.2026)
- Wildlife and Countryside Act 1981, section 13 (retrieved 21.10.2026)
- Consumer Rights Act 2015, section 9 (retrieved 21.10.2026)
- Business Companion, Consumer Rights Act 2015 (retrieved 21.10.2026)
- GOV.UK, reporting product safety issues (retrieved 21.10.2026)
- Wildlife Trusts, sphagnum (retrieved 21.10.2026)