Sphagnum moss holds water and works in the substrate; cushion moss is live decorative greenery on top. Here is how to tell them apart and when to use each.
Sphagnum moss and the fresh green moss you place on top of a terrarium are not the same thing. Sphagnum is a water-retaining moss that works mainly in and under the soil, while decorative moss such as cushion moss is live greenery meant to be seen. Use sphagnum for moisture management and cushion moss for the finishing touch.
Walk into a garden centre and almost everything soft and green gets called "moss". In a terrarium or bottle garden, though, it pays to separate two roles: moss that works out of sight, and moss that works as decoration. Mixing them up is one of the most common reasons a moss layer turns brown or slimy.
Sphagnum is known for how much water it can hold compared to its own weight. That makes it useful as a moisture buffer, for example as a thin layer between drainage and soil or around the roots of a plant. Regular decorative moss, by contrast, is chosen for its look: dense, bright green, and neat enough to form small hills or a miniature meadow.
Sphagnum is a group of mosses that grow in wet, boggy places. Garden and plant suppliers usually sell it dried or as fibre. Once it is moistened it soaks up water like a sponge and releases it slowly. In a closed terrarium that behaviour can help keep the lower layers evenly moist, but it also means you can easily overdo it: a sphagnum layer that is soaked all the way through keeps the soil wet for a long time.
When people say regular moss for a terrarium, they usually mean live moss that is sold for decoration. Cushion moss, also called bun moss or pillow moss (Leucobryum glaucum), is a well-known example. It forms rounded, pillow-like mounds in a fresh green shade and is ideal for making small hills, covering bare spots in the soil or softening the edges of a landscape in glass.
Cushion moss is a surface plant. It sits on top of the substrate, on pebbles, gravel or sand, as long as there is good drainage and some humidity. It does not need to be buried, and it looks best when you can actually see it.
Good news: using live cushion moss is simple. The pieces are ready to use. If a piece carries loose debris, clean it gently with your hand or a soft brush first. Our live cushion moss comes as three pieces per bag, roughly 8 to 15 cm across, and chosen at random depending on availability. A piece that is too big is easy to resize: simply break it into smaller mounds.
Create small hills, build a mini grass field or hide a tricky bare patch. Because the moss grows straight on the surface, you do not need to plant it into the soil.
Yes, and many people do. Use a thin layer of sphagnum beneath the soil if you want an extra moisture buffer, and finish the top with cushion moss for colour and texture. The key is restraint. Keep the sphagnum layer thin and always make sure the drainage layer underneath can do its job, so the roots never sit in standing water.
Cushion moss belongs on the surface. Covering it with soil blocks the light and humidity it needs and it will turn brown.
Wet moss is fine, dripping moss is not. In a closed terrarium, water has nowhere to go, so mist lightly rather than pouring.
A moss that looks perfect in a photo may not do the job you need. Decide first whether you want to manage moisture or add decoration, then pick the moss that fits.
No. Sphagnum is a water-retaining moss that is mostly used inside the substrate, while cushion moss is a live decorative moss that sits on top and is meant to be seen.
Yes. Cushion moss does well directly on the soil surface, pebbles, gravel or sand, provided drainage is good and the moss gets some humidity, for example from occasional misting.
Cushion moss is easy to resize. Gently break the piece into smaller mounds and place them where you need them.
No. Many terrariums look great with only cushion moss on top. Sphagnum is an optional extra for moisture control.
Ready to give your glass landscape a soft green finish? Browse more terrarium supplies, or read our guide to using sphagnum moss in your terrarium.
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