Reindeer Lichen Identification Guide

What You Are Standing In When You Find It

Reindeer Lichen is a ground-layer organism of cold, open, nutrient-poor country. The classic setting is boreal forest: an open stand of pine, spruce or larch on sandy or rocky soil, with almost no herb layer and a continuous pale carpet underfoot that crunches when dry and springs back when wet. It is equally at home on arctic and alpine tundra, on sandy pine barrens far south of the boreal zone, on exposed rock ledges with a thin skin of humus, and in bogs on old hummocks.

The first impression is not of an individual but of a surface. From a distance the mat reads as a grey-white or ash-coloured haze spreading across the ground between heather, crowberry and bare rock, sometimes over many square metres. Only when you crouch does it resolve into thousands of separate miniature shrubs, each one a few centimetres tall and branched like a bleached coral.

It is worth being clear about what this organism is, because it changes how you examine it. This is a lichen — a fungus living in partnership with a photosynthetic alga — not a mushroom. There is no cap, no gills, no stalk in the mushroom sense, and, in practice, nothing to take a spore print from.

Reading The Growth Form

The upright structures are called podetia. In this species they stand 4 to 10 cm tall, occasionally more in sheltered sites, and are repeatedly branched into a bushy, open, tree-like shrub. There is no leafy basal rosette persisting at the ground — the squamules that started the colony wither away, so what you see is the branched skeleton alone.

Pick up a single podetium and hold it against a dark glove. Trace the branching. In Cladonia rangiferina the main stems divide mostly into three or four branches at each axil, giving a repeatedly forking, candelabra-like structure. Lower branches are stouter; the divisions become progressively finer toward the top, ending in slender tapering tips.

Now check the tips, which is one of the most useful characters. The ultimate branchlets typically nod or curve, and — critically — the tips across one clump tend to point predominantly in one direction, as if combed by wind. Look at the whole colony rather than one branch: the mat has a directional grain.

Tip colour matters too. The fine ends are usually darkened, brown to blackish-brown, contrasting with the pale body of the plant.

Reading Colour And Surface

Colour is the second big character. Fresh, well-lit material is pale ashy grey to whitish-grey, sometimes faintly bluish, with no yellow or green cast. Hold a branch beside a sheet of white paper in daylight: it should read as grey, not as chartreuse, straw or yellow-green.

The surface is matte and slightly downy or cottony rather than shiny — under a hand lens it looks felted, because this species lacks a smooth continuous outer skin and instead has a loose, arachnoid covering of hyphae. Wet a branch and the felting mats down; dry material feels brittle and papery.

Internal Structure

Snap a stouter lower branch cleanly and look at the break with a lens. The podetia are hollow, with a central canal running up the stem, and the wall is thin and slightly fibrous. This hollowness is shared across the reindeer lichen group and is worth confirming, because several superficially similar ground lichens are solid.

The texture test is simple and reversible. Dry material is stiff, crisp and shatters between finger and thumb; the same colony after rain or heavy dew is soft, rubbery and can be squeezed without breaking. Always assess texture and colour on material in a known moisture state, because dry lichen looks paler and greyer than wet.

Fruiting Bodies And Why There Is No Spore Print

Spore-producing structures are rarely developed in this species. When they do occur, they take the form of tiny brown apothecia — minute dark buttons perched at the very tips of the finest branchlets, often less than a millimetre across. Look for them with a lens on old, well-established colonies; most collections will not have them.

Because the fungus so seldom fruits and reproduces mainly by fragmentation, the spore-print technique used for mushrooms simply does not apply. Identification here rests on growth architecture, branching pattern, tip orientation, colour and surface texture instead. If you are documenting a specimen, record the whole clump silhouette and a close-up of a single branching axis rather than looking for a spore deposit.

Substrate, Season And Ecology

Reindeer Lichen grows on soil, humus, sand, peat, rotting wood and thin soil over rock. It is strongly associated with acidic, nitrogen-poor, well-lit ground and disappears where fertility rises or where dense vegetation shades it out. It is not a plant parasite and takes nothing from the trees it grows among.

Growth is extremely slow — on the order of a few millimetres per year — so a deep continuous mat represents decades of undisturbed conditions. That slowness makes the species a useful indicator of long-unburned, undisturbed and unpolluted ground; it is sensitive to air pollution and to trampling, and mats recover from damage over decades rather than seasons.

Unlike mushrooms, there is no fruiting season to track. The colony is perennial and present year-round, changing only in texture and apparent colour with moisture. Winter snow cover protects the mats; late-summer drought makes them brittle and easily broken by footsteps.

Separating It From Look-alikes On Morphology

Star-tipped Reindeer Lichen (Cladonia stellaris). Forms dense, rounded, cushion-like heads that look like little pompoms or cauliflowers, and the branch tips at the top of each head radiate in all directions rather than nodding one way. Colour is usually yellowish-green to pale yellow rather than pure grey. The overall silhouette is the quickest separation: rounded compact head versus open, spreading, wind-combed shrub.

Green Reindeer Lichen (Cladonia arbuscula) and C. mitis. These share the one-way nodding tips and open shrubby form, but the colour carries a distinct yellowish or greenish-yellow tint. Side-by-side against white paper the difference is obvious; alone in the field it takes practice. Branching in these species also tends more toward divisions in twos and threes rather than the consistent threes and fours seen here.

Cladonia uncialis. Branches are stouter, smoother, shinier and often flattened or angular, with a firmer outer skin and conspicuous small perforations at the axils, and the colour is a more yellowish grey-green.

Cladonia portentosa and other open reindeer lichens. Bushier and more diffusely branched, often with tips pointing in varied directions and a slight yellow cast.

Cup lichens (Cladonia species such as C. pyxidata) and pixie-cup forms. Immediately different: they produce trumpet or goblet-shaped podetia and usually retain green basal squamules at ground level.

Mosses such as Racomitrium. Grey-green and mat-forming from a distance, but under a lens they show flat leaves along a stem rather than hollow, repeatedly forking, leafless branches.

A Quick Field Sequence

1. Continuous pale mat on acidic, open, nutrient-poor ground.
2. Shrubby leafless podetia 4 to 10 cm tall, no basal squamules.
3. Branching mostly in threes and fours at each axil.
4. Fine tips brown-tipped and nodding predominantly in one direction.
5. Colour ashy grey to whitish with no yellow cast; surface felted, not shiny.
6. Branches hollow when snapped; brittle when dry, rubbery when wet.