British Soldiers Lichen Identification Guide

First Impression and the Setting

You come across this one at knee height or lower, usually while looking at something else. A weathered fence rail, the flat top of a rotting stump, an old railway sleeper, a bare patch of acidic sandy soil beside a path, or a mossy boulder in an open pine or oak wood: the substrate is poor, acidic and undisturbed, and the light is reasonably good.

What catches the eye is a scatter of tiny scarlet dots, as though someone had flicked red paint across a grey-green crust. Get down to the surface and the structure resolves: a low mat of small greenish scales, and rising from it a forest of pale grey-green to yellowish stalks between about 3 and 20 millimetres tall, each finished with a lumpy red head. That combination of stalks plus red tips is the whole identification in outline; the rest is detail work that separates it from its relatives.

Remember that this is a lichen, a partnership of a fungus with a green alga, not a mushroom. Several of the field steps used on gilled fungi have no equivalent here, and the steps that replace them are set out below.

Step One: The Primary Thallus

Look first at the mat on the substrate. It is squamulose, meaning it is built of small, flattish, leaf-like scales 1 to 4 millimetres across, often with lobed or slightly notched margins and a habit of curling upward at the edges. The upper face is grey-green to yellow-green, the underside distinctly paler, whitish to pale grey.

That yellowish tinge to the green matters and is worth checking in good light: it comes from usnic acid in the cortex, and it separates this species from the several red-fruited relatives whose thallus is a colder, greyer green with no yellow in it. The squamules persist in this species rather than withering away, so a well-established colony usually shows both the mat and the stalks together.

Step Two: The Podetia

The upright stalks are called podetia. In this species they are 3 to 20 millimetres tall, roughly 0.5 to 2 millimetres thick, and irregular. Some are simple and unbranched; others fork once or several times near the top, and old ones may become distorted or slightly flattened.

The critical negative character is the absence of a cup. This species does not usually form the neat goblet or trumpet mouths seen in the pixie cups; where a hollow does open at the tip it is irregular and ragged rather than a symmetrical funnel.

Examine the podetial surface with a hand lens. It is corticate but uneven, roughened with granules and small squamules that increase towards the base, and often greenish grey with a yellowish cast. It is not powdery. Rub a stalk gently between finger and thumb: fine flour-like soredia would come away as dust in a sorediate species, whereas here the surface holds together as a granular skin.

Step Three: The Apothecia

The red heads are apothecia, the spore-producing discs of the fungal partner. In this species they are comparatively large, often 1 to 3 millimetres across, and typically confluent, several fusing into a single knobbly, brain-like or coral-like mass that caps the podetium and may be broader than the stalk carrying it.

The colour is a strong scarlet to blood red, matt rather than glossy, and it holds well even in dried herbarium material. That pigment is a fungal product rather than anything to do with the alga, and it is the feature that gives the lichen its common name.

While you have the lens out, hunt along the squamule margins and podetial tips for pycnidia, minute flask-shaped bodies that in this species contain a red gelatinous mass. Squeeze one against a slide and the red jelly is quite distinctive.

Step Four: What Replaces a Spore Print

There is no spore print to take: a lichen does not shed a visible spore mass onto paper the way a gilled mushroom does. The equivalent step is a razor section of an apothecium viewed under a microscope, showing a hymenium with asci and colourless, single-celled, ellipsoid ascospores.

In the field, the closest practical substitutes are structural and chemical. Structurally, note whether the tips are cupped or not, whether the surface is granular or floury, and whether the apothecia are large and confluent or small and separate. Chemically, spot tests can be applied with a fine brush to the podetial surface. The yellow-green cast points to usnic acid, and this species is characterised by a barbatic acid chemistry with the red pigment rhodocladonic acid in the apothecia. A K test that produces a strong immediate yellow turning red would indicate a different chemistry and therefore a different species.

Substrate, Season and Ecology

The characteristic substrates are decorticated rotting wood, old stumps, fallen logs that have lost their bark, fence posts and rails, and, less commonly, acidic mineral soil, peaty banks and mossy rock ledges. It tolerates full sun and dry, thin habitats and does well on disturbed acidic ground where competition from vascular plants is weak.

Lichens do not have a fruiting season in the fungal sense; the podetia are perennial and the apothecia persist across seasons, so the colony can be examined at any time of year. What changes is condition: after rain the thallus swells and its green deepens, while in drought the squamules shrink, curl and pale, making the red caps look even more prominent.

Ecologically it is a pioneer, colonising bare, nutrient-poor surfaces where the alga supplies carbon through photosynthesis and the fungus supplies structure, mineral capture and protection from drying. Growth is slow, and an established patch may represent many years of accumulation, which is why such colonies are worth photographing rather than collecting.

Separating the Red-Tipped Cladonias

Cladonia macilenta has slender, mostly unbranched podetia whose surface is farinose, covered in fine flour-like soredia that rub off as dust, and its apothecia are small and discrete rather than lumpy and confluent. Its thallus lacks the yellowish tone.

Cladonia floerkeana has podetia clad in granules and small squamules, but again the apothecia are typically smaller and more separate, and the overall colour is a greyer green.

Cladonia bellidiflora carries dense leafy squamules right up the podetium, so the stalks look shaggy, and it belongs to cool, montane and northern habitats.

Cladonia pleurota and Cladonia deformis both make true cups. Their podetia flare into distinct goblets with sorediate surfaces, and the red apothecia sit around the cup rim rather than capping a solid stalk.

Cladonia didyma has smoother, less granular podetia and, again, less massive apothecia.

Finally, do not confuse the red apothecia with red fruits of mosses or with red algae films. Under a lens the apothecia are firm, waxy discs continuous with the podetial tissue, not separate capsules on a translucent seta.

Compact Field Routine

Confirm a squamulose grey-green to yellow-green basal mat; confirm upright podetia without regular cups; confirm large, lumpy, confluent scarlet apothecia; check that the podetial surface is granular rather than powdery; note acidic wood or bare acidic soil as substrate. Five checks and few alternatives survive.