Moss keeps very well before planting: a clear closed box, a damp sheet of kitchen paper underneath, indirect light, and it holds for several weeks. The two mistakes that kill it are always the same — leaving it in its sealed dark packaging, or standing it in water.

Why it keeps so well

Moss has neither roots nor vessels: it does not depend on a substrate. It takes up water across its whole surface and withstands spells of drying out that would kill an ordinary plant.

Many species enter a dormant state when they dry: they look dead, then start again as soon as the moisture returns. That is why moss that arrives dry and dull is not necessarily lost.

What it cannot take is being submerged or kept in the dark.

The method that works

A clear container with a lid. A food box, a jar, a salad tub. Clear is the important part: moss needs light even while it waits.

A damp base, no standing water. A sheet of kitchen paper wetted and wrung out, or a thin layer of damp sphagnum. The moss sits on top of it, it does not soak in it.

Indirect light. Near a window, never in the sun — a closed box in full sun turns into an oven.

A lid resting on top, not locked down. A little air passes through and the condensation does not run away with itself.

One inspection a week. Remove anything going white or mouldy, and re-dampen if the base has dried out.

Under these conditions, allow three to six weeks with no noticeable loss. Past a month the moss is still alive but picks up less vigorously once planted.

In the fridge

For longer storage, cold slows everything down. Same box, same moisture, in the salad drawer.

Two precautions: do not use a perfectly airtight box, and bring the moss out gradually — a few hours at room temperature before handling it. Going straight from the cold into a warm terrarium marks it.

Reviving moss that arrives dry

This happens after transport, and it is usually not serious.

1. Lay it in the box on a damp base.
2. Mist it lightly, without soaking it.
3. Close the box and put it in indirect light.
4. Wait two to three weeks.

If green appears at the tips, it is coming back. The parts that stay brown will not turn green again, but they will be covered by new growth once the moss is in place — see Moss turning brown.

The mistakes that kill it

Leaving it in its sealed, opaque packaging. This is the first cause of loss. With no light and no air, it goes white and then mouldy within a week or two. Open the parcel the day it arrives.

Standing it in water. Moss left submerged for more than a few minutes suffocates. Damp, yes; underwater, no.

Laying it on sodden compost. Same problem, more slowly.

Full sun. A closed box in the sun heats up very quickly.

Very hard water. It leaves a whitish deposit that smothers the moss. Rainwater or deionised water is better.

Before laying it

A quick rinse under clean water, without rubbing, removes dust and debris. Use tongs to take out twigs, dead leaves and any visible insects — in a closed setting, everything left behind decays.

Then lay it using the method in How to lay moss in a terrarium: damp substrate, cut to shape with scissors, firm contact, misting.

And if the terrarium is not ready

That is exactly the situation. There is no rush: moss in a box will happily wait until you have the container, the substrate and the plants. Better to keep it waiting for three weeks than to rush a build in order to use it quickly.

Choosing species for the effect you want is covered in Mosses for terrariums, and our selection is in the mosses section.

Sources

• Creating a Closed Terrarium — Penn State Extension
• How to Design a Closed-System Terrarium — Mississippi State University Extension