Reindeer moss and reindeer lichen are the same thing under two names, and the honest one is reindeer lichen. The organism, Cladonia rangiferina and its close relatives, is a lichen, not a true moss, so there is no real contest between the two names, only a common one and a correct one. If you have wondered whether you were comparing two different things, you were not; you were looking at one organism wearing a misleading label.
Same organism, two names
The pale, springy, branching stuff sold by the bag for moss walls, floristry, wreaths and model railway scenery is the same organism whether the packet calls it reindeer moss or reindeer lichen. Botanists and lichenologists say reindeer lichen; craft shops, decorators and older field guides tend to say reindeer moss. The plant, if you can call it that, does not change; only the name does. So the useful question is not which of the two it is, but why one name is right and the other is not.
Why it is a lichen, not a moss
A lichen is not a single organism at all but a partnership, a fungus and an alga living together as one, the fungus giving structure and the alga making food from light. A true moss, by contrast, is a plant in its own right, a bryophyte with tiny leaves arranged around a stem. That difference in what they are shows plainly in what they feel like. Reindeer lichen is dry, brittle and cartilaginous, and it snaps when you bend it; a moss is soft and leafy, and it tears. The lichen is grey-white or pale silvery green; a moss is a fresher, livelier green. The general test for separating the groups is set out in moss, lichen, liverwort or algae.
Why the "moss" name stuck
The name persists because, at arm's length, the stuff behaves like a moss. It is low and soft-looking, forms springy carpets, and grows in the same cool, damp, northern places where mosses thrive. Only up close, or when you try to treat it like a moss and find it wants nothing you would give a plant, does the difference become plain. It sits alongside a whole family of everyday misnomers that hang the word "moss" on things that are not: the marimo "moss ball", which is an alga, covered in the marimo moss ball, and Spanish "moss", which is a flowering plant. The fuller story of this particular one is in reindeer moss, the lichen everyone calls moss.
How it lives in the wild
Across the tundra and on northern heaths, reindeer lichen forms vast pale carpets, springy underfoot and stretching for miles. It is a winter mainstay for reindeer and caribou, which smell it out and dig it from beneath the snow, and it gives the organism its name. It grows extraordinarily slowly, often only a few millimetres a year, so those carpets represent decades of quiet growth and recover painfully slowly once grazed or stripped. That slowness is worth holding in mind whenever a bag of it turns up cheaply on a craft shelf; the material may well be older than the person buying it.
The preserved decorative form
Almost all the reindeer moss you can buy has been preserved. Its structure is stabilised with glycerine and it is usually dyed a vivid green, so it stays soft and pliable indefinitely without water or light. In that state it is the workhorse of preserved moss walls, wreaths, terrarium dressing and model scenery, valued for a fine, springy, branching texture that no living moss quite matches. It is no longer alive and needs no care beyond keeping it out of direct sun, which fades the dye, and away from damp, which can turn it sticky. Its place in wall panels is covered in preserved moss walls.
Does the distinction matter?
For decoration, not much: the panel on your wall looks the same whichever name is on the label. It matters when you try to keep it alive or grow it, because a lichen this slow will not oblige, and it matters for conscience, since knowing the harvest comes from slow-growing wild carpets is a reason to buy the preserved form sparingly and forage, if at all, only where it is genuinely abundant. Knowing what it really is changes nothing about how well it looks, but it does explain why it will never grow for you and why it is worth treating as the finite thing it is.
Common questions
Is reindeer moss the same as reindeer lichen?
Yes. They are two names for the same organism, Cladonia rangiferina and its close relatives. Reindeer lichen is the accurate name and reindeer moss the common but misleading one, since the organism is a lichen rather than a true moss.
Why is reindeer lichen called a moss?
Because at a glance it behaves like one: it is low, pale and springy, forms carpets and grows in the same cool, damp northern places as moss. The name is old and stuck long before the difference between mosses and lichens was widely understood.
How do I tell reindeer lichen from a true moss?
Feel it and look at the colour. Reindeer lichen is dry, brittle and cartilaginous, snapping rather than tearing, and it is grey-white or pale silvery green. A true moss is soft and leafy, tears rather than snaps, and is a fresher green, made of tiny leaves around a stem.
Can you grow reindeer moss?
Not in any practical sense. It grows extraordinarily slowly, often only a few millimetres a year, and does not lend itself to cultivation, which is why the commercial supply is gathered from the wild and why the harvest raises real sustainability questions.