Not everything called "moss" is actually a moss.
Irish moss, Spanish moss, club moss and reindeer moss are all popular, all widely sold, and none of them are true mosses — they're a seaweed, a bromeliad, a completely different plant lineage, and a lichen, respectively. Feather moss, cushion moss, sphagnum, carpet moss and sheet moss genuinely are mosses in the strict botanical sense: no roots, no flowers, no seeds, just quiet, ancient plants absorbing water directly through their surface.
This guide sorts out which is which, and which ones actually make sense for a terrarium or mossarium.
What makes a plant a "true" moss?
A true moss is a bryophyte: a plant with no roots, no vascular system for moving water internally, no flowers and no seeds. It absorbs water and nutrients directly across its surface, anchors itself with simple thread-like rhizoids, and reproduces using spores rather than flowers.
That single structural fact explains almost everything about how moss behaves in a terrarium — why it thrives in humidity, why it can't be watered like a houseplant, and why it recovers so readily from being pressed and shipped. It's also exactly what separates a true moss from the moss-in-name-only plants further down this guide.
True mosses
What is feather moss?
Feather moss is a UK woodland moss — commonly species from the genera Hypnum and Kindbergia — with loose, finely branching growth that spreads into soft, irregular ground cover, like a miniature forest floor.
In a terrarium it creates a naturalistic, spreading look and fills a base layer readily. It dries a little faster than cushion moss, since more of its surface is exposed to air, so it wants slightly more frequent misting in an open container. Read our full guide to feather moss for the specific species involved.
What is cushion moss (bun moss)?
Cushion moss — often sold as bun moss, usually Leucobryum glaucum — is a true moss that grows in dense, rounded mounds rather than spreading flat, each piece behaving like a self-contained little hill.
It's the better choice when you want a sculptural focal point rather than ground cover, and it holds moisture in its dense structure for longer than feather moss — more forgiving if you're prone to under-watering.
What is sphagnum moss?
Sphagnum is a genus of true moss best known for forming peat bogs and for its extraordinary capacity to hold water, often many times its own dry weight.
It's less commonly used as the visible, decorative moss in a terrarium and more often used functionally — packed around roots to retain moisture, or layered between drainage material and substrate. If your terrarium has distinct layers, a thin band of sphagnum is likely doing quiet, unglamorous work in there already.
What is carpet moss?
Carpet moss isn't one species so much as a description — a common name for various low, flat-growing true mosses (often Hypnum or Thuidium species) that form a dense, even mat rather than individual clumps.
It's feather moss's tidier cousin: a similar spreading habit, but a smoother, more uniform finish, good for full even ground coverage in a larger terrarium or vivarium base.
What is sheet moss?
Sheet moss is moss harvested and sold in large, intact mats rather than loose pieces — grown as a connected sheet and lifted largely whole.
It's popular in floristry and larger terrarium or vivarium builds where you want to line a wide surface in one go. Botanically it's usually one of the same flat-growing woodland species as carpet or feather moss; "sheet" describes the harvest and form, not a different plant.
Moss impostors: popular "mosses" that aren't moss at all
Worth knowing, if only so a plant label doesn't send you down the wrong path when shopping for a terrarium.
Is Irish moss actually a moss?
No — and "Irish moss" is a genuinely confusing case because it refers to two unrelated things. In food and brewing, it's Chondrus crispus, a red seaweed harvested from Atlantic coastlines. In gardening, "Irish moss" almost always means Sagina subulata, a low flowering groundcover in the carnation family. Neither is a true moss, and neither suits a terrarium the way feather or cushion moss does.
Is Spanish moss a true moss?
No. Spanish moss (Tillandsia usneoides) is the pale, trailing, beard-like plant draped over oak trees in the American South — but despite the name, it's an epiphytic bromeliad, a relative of the pineapple, with no roots. It absorbs water and nutrients through tiny scales on its surface, and it wants open-air ventilation rather than the enclosed humidity a mossarium provides.
Is club moss a true moss?
No. Club moss (Lycopodium and related genera) looks like an upright, architectural moss, but it belongs to an older, separate lineage called lycophytes — technically closer to ferns than to true moss, despite the shared spore-based reproduction.
Is reindeer moss a type of moss?
No — reindeer moss isn't a plant at all. It's a lichen, a composite organism formed from a fungus and an algae living together, popular in model-making and dried floral displays. It doesn't respond to misting the way living moss does, and most commercially sold reindeer moss has been dyed and preserved rather than kept alive.
Which moss should you actually use for a terrarium?
For a live, closed or semi-closed mossarium, the true mosses above are the ones worth building with — they're adapted to exactly the humid, low-light conditions a terrarium provides.
- Want a natural, woodland-floor look? Feather moss or carpet moss.
- Want a sculptural focal point? Cushion (bun) moss.
- Lining a large surface in one go? Sheet moss.
- Need a functional moisture-holding layer, not a visible one? Sphagnum.
For a full side-by-side comparison of the two most commonly used types, read Cushion Moss vs Feather Moss: Which Is Best for Your Terrarium? Once you've picked a type, our live moss care guide covers watering, light and ventilation in detail, and What Is a Mossarium? is the place to start if you haven't built one yet.
Browse our full live moss collection to see feather and cushion moss available now.
Frequently asked questions
Is all moss safe to use in a terrarium?
True mosses generally are, since they're adapted to the humid, enclosed conditions a terrarium creates. The "impostor" plants above — Irish moss, Spanish moss, club moss and reindeer moss — either need different conditions entirely or, in reindeer moss's case, usually aren't alive to begin with.
Why do so many unrelated plants get called "moss"?
Mostly because of appearance rather than botany. Anything low-growing, textured and green — or, in Spanish moss's case, silvery-grey and trailing — tends to pick up "moss" as a common name regardless of what it's actually related to. Common names describe how a plant looks; only the scientific name reliably tells you what it is.
Can you mix different types of true moss in one terrarium?
Yes — feather and cushion moss are often combined for contrast between spreading ground cover and a rounded focal point. They can dry at slightly different rates, so keep an eye on both rather than assuming one misting schedule suits everything in the container.
Is sphagnum moss the same as peat moss?
Related but not identical. Peat moss is decomposed, compressed sphagnum harvested from bogs, usually sold dried as a soil additive. Living sphagnum, as used in a terrarium, is the actively growing plant itself.