Most Christmas terrariums are built to last until Twelfth Night. Fake snow, bottle-brush trees, a string of battery lights tucked under some dried moss: pretty for a few weeks, then dusty, then in the bin. A living Christmas terrarium is a different thing. Build it with real moss and the right decorations and it is still green in January, and in March, and long after the tree has gone.
The trick is simple. The festive part of the scene has to be made of things that cannot rot, leak or poison the soil, and the living part has to be treated exactly like any other terrarium. Here is how to do both.
Can a Christmas terrarium stay alive?
Yes. Moss is one of the easiest things to keep under glass, and nothing about December changes that. What kills most festive terrariums is what goes in alongside the moss: salt-based fake snow, cut greenery and berries that turn to mush, glitter that coats every surface, and battery packs buried in damp substrate.
So think of it as two jobs. First, build a healthy moss terrarium. Second, dress it with decorations that are happy to sit in a humid jar for months. Keep anything else outside the glass.
Choosing a jar for a Christmas terrarium
Almost any clear glass container works. Each style gives a slightly different look:
- A cork-lidded jar: the classic closed terrarium. It makes a self-contained little world that needs watering only occasionally, and it is the easiest to give as a present.
- A cloche or glass dome on a base: lovely for a mantelpiece-style scene you can lift off and rearrange. Domes are usually less airtight, so expect to mist more often.
- An apothecary or sweet jar: tall and elegant, with room for a twig "tree" or a stone outcrop.
Choose clear glass rather than tinted, and a lid that lets light through. The RHS notes that opaque lids reduce light levels and metal screw-tops can rust in a humid jar (RHS: bottle gardens and terrariums). A wide mouth makes building far easier on a first attempt.
Which moss gives the best winter look?
Two mosses do most of the work in a winter woodland scene.
Feather moss as the forest floor
Feather moss is soft, branching and low, so it reads as a woodland floor at miniature scale. It is also the best "tree" moss you can get.
"The green fronds of feather moss are reminiscent of evergreen trees like spruce and fir... it sits well alongside any of your Christmas home decor," says Morgan at The Moss Fairy.
Cushion moss as snowy hills
Cushion (bun) moss grows in rounded domes. Two or three mounds of different sizes make rolling hills behind a feather moss foreground, and they give the eye somewhere to rest.
What not to put in a Christmas terrarium
This is the part most festive guides skip, because most of them are not trying to keep anything alive. If your terrarium is living, leave these out:
- Fake snow, Epsom salt or table salt. Many craft guides use salt as snow. Salt draws water out of plant roots and builds up in soil, which is why road salt damages plants (University of Wisconsin–Madison Extension). In a sealed jar it has nowhere to go.
- Glitter and flock. It sticks to wet moss and glass, cannot be picked out and blocks light from the moss beneath.
- Cut holly, ivy, fir sprigs and real berries. Cut stems and fruit start to decay in warm, humid air. The RHS advises removing dead plant material from terrariums promptly because it rots and grows mould. Put the real greenery around the outside of the jar instead.
- Battery packs and wiring inside the glass. Constant condensation is no friend to batteries or electrical contacts, and a pack buried under moss is impossible to reach.
- Painted resin, cheap plastic figures and anything glued. Paint can flake and glue can soften in permanent humidity. If you do want a figurine, check it is fully sealed, and expect to wipe it now and then.
- Too many things. A scene that fills the jar leaves no air and no room for the moss to look like a landscape.
Morgan once came across a terrarium that took the festive brief all the way. "I once saw a full-on miniature Jesus nativity terrarium with a baby manger and all. Think they sourced dolls' house sized props and figures. It looked great... if Jesus had been born in a jungle! A+ for inventiveness. F for historical accuracy," says Morgan. Inventive is good. Just make sure the props are things that can live in a jungle too.
Decorations that are safe inside a living jar
Choose materials that do not rot, leach or shed:
- Glass: a tiny glass bauble or a marble catches the light beautifully.
- Brass and other solid metal: a small solid brass frog is a quiet nod to the woodland, and in a humid jar brass slowly takes on a soft, aged patina rather than falling apart.
- Stone and pebbles: a pale stone or two makes a convincing "frosted" outcrop, and a flat one can carry a figure above the moss.
- Glazed ceramic: tiny glazed houses or animals are fine as long as the glaze is intact.
- Clean, dry twigs: a small bare twig makes a winter tree. Rinse it and pour boiling water over it before use, as our mould guide explains, to cut down the fuzz that fresh wood often grows.
Step by step: building a winter woodland terrarium
The layers are the same as any moss terrarium. If you have never built one, our beginner's guide to making a moss terrarium covers them in more detail.
- Clean the jar. Hot water, a good rinse and a dry cloth.
- Add a drainage layer. A couple of centimetres of clay pebbles or gravel, so excess water has somewhere to go.
- Add a thin layer of activated charcoal to help keep a closed jar fresh.
- Add substrate. A few centimetres of light terrarium substrate, sloped higher at the back. That slope does a lot of work in a small landscape.
- Place the hills first. Set cushion moss mounds at the back and sides, pressing each one firmly into the substrate. The New York Botanical Garden notes that moss does not do well with an air gap between it and the soil (NYBG Plant Information).
- Lay the forest floor. Tuck feather moss across the front and between the hills, again pressed down well.
- Add the festive pieces. A twig tree, a pale stone, one small metal or glass figure. Use tweezers or a chopstick, and stop before you think you are finished.
- Water lightly. A few sprays from a mister, run down the inside of the glass, is plenty. The moss should be damp, not sitting in water.
- Close the lid and watch the glass over the next few days. A little condensation that comes and goes means the balance is right.
If you would rather have everything in one box, a kit takes the guesswork out. Asked which kit to hand to a first-timer for a festive build on a December evening, Morgan's answer was: "A cork lid feather kit. There's something quite satisfying about building up something from its base components, then watering it and sealing it with the big chunky cork lid. It delivers a satisfying sense of accomplishment." That's our Live Feather Moss Terrarium Kit. If you already have a jar or cloche you love, the DIY Terrarium Starter Kit has every layer except the glass.
How to add fairy lights to a terrarium (without killing it)
Lights are what make a Christmas terrarium glow, but they belong on the outside. Coil a string of warm-white LED fairy lights around the base of the jar, or drape them behind it, and the glass will catch and scatter the light just as well as if they were inside. LEDs also stay cool, which matters for something sitting right next to living moss.
It keeps the batteries dry, keeps wires out of the substrate, and means the lights can come off on Twelfth Night while the terrarium stays exactly as it is.
Where to put a Christmas terrarium in a heated house
Not on the mantelpiece above a lit fire, and not on a shelf over a radiator. The RHS advises keeping terrariums away from heat sources and out of direct summer sun, in bright, indirect light for at least six hours a day. In winter a south- or west-facing window is fine, because the sun is weak.
A sideboard or windowsill in a cooler room is ideal. If you want it as a table centrepiece for Christmas Day, move it there for the meal and back afterwards.
Giving a Christmas terrarium as a present
Build it a week or two ahead. A new terrarium often needs a little adjusting while it settles, and it is better for that to happen at your house than under the recipient's tree. Wipe the glass, check there is light condensation but no puddles, and add a note with the two rules that matter: bright indirect light, and a light mist only when the glass stays dry.
If you can't be there to hand it over, send the making instead. A kit is easier to post than a planted jar, gives the recipient their own December-evening project and arrives with everything they need. We deliver free across the UK and ship internationally, and we can gift wrap it if it's going straight to them. For more on why a terrarium makes such a good present, read why a moss terrarium is the perfect gift.
After Christmas: keep the terrarium
When the decorations come down, lift the festive pieces out with tweezers, leave the moss and stones, and you have an everyday terrarium. The moss doesn't mind what season it is.
Frequently asked questions
Can terrariums survive winter?
Indoors, easily. Moss is happy in a cool room, and lower winter light is fine as long as the terrarium is near a window. The real winter risks are heat and dry air: keep it off radiators and away from fires, and check the glass for condensation now and then.
What should you not put in a terrarium?
Salt or salt-based fake snow, glitter, cut greenery, fresh berries, batteries, and anything painted or glued that could break down in constant humidity. Garden soil is also best avoided, because it compacts and brings in mould spores.
How do you make a homemade mini terrarium?
Use a small clear jar with a lid, a thin drainage layer, a little substrate and a few pieces of live moss pressed firmly down. Mist lightly, close it and keep it in bright, indirect light. Small jars dry out and overheat faster than big ones, so check them a little more often.
Can you put fairy lights inside a terrarium?
You can for a short-lived display, but in a living terrarium it is better to keep them outside the glass. The humidity is hard on batteries and contacts, and wrapping the lights around the jar gives much the same glow.
How long will a Christmas terrarium last?
A living moss terrarium built with the decorations above can last for years, long after Christmas is over. A scene made with fake snow, cut greenery and craft moss will usually look tired within a few weeks.
Ready to start? Our Cork Lid Mini Terrarium Kit and Feather Moss Terrarium Kit come with fresh live moss and every layer in the right order, ready for a quiet December evening.