Pixie Cup Lichen

The Pixie Cup is the archetypal cup lichen: a squat, grey-green stalk that opens abruptly into a broad goblet, as if a tiny wine glass had been set down among the moss. Whole colonies of these cups grow together on banks, rock ledges and mossy soil, and their neat geometry makes them one of the first lichens most people learn to notice.

Cladonia pyxidata belongs to Cladonia, a genus with a two-storey construction: a primary thallus of small leafy squamules pressed to the ground, and secondary upright structures — here the cups — rising from it. The cups are not solid; they are hollow, open-topped and continuous with the hollow stalk beneath.

What distinguishes this species within a confusing group is the surface of the podetium. Rather than being smooth or coated in flour-like soredia, it is covered with coarse granules and small scales, giving a pebbled or gritty texture inside and outside the cup. That texture, combined with wide, shallow, abruptly flaring goblets on short stalks, is the working field character.

Primary thallus

The base is a mat of squamules 2–6 mm long, grey-green to olive above, white underneath, with rounded or shallowly lobed and often slightly upturned margins. These leafy scales persist and are usually easy to see between the cups.

Podetia and cups

Podetia are short and stout, typically 5–25 mm tall, expanding fairly abruptly into a broad cup 3–10 mm wide — usually as wide as or wider than the stalk is tall, giving a squat trumpet or goblet profile. The cups are regular, shallow to moderately deep, and hollow; the base of the cup is often perforated in the centre. Cups may occasionally proliferate, with a second small cup growing from the rim of the first.

Surface texture

The whole podetium, inside the cup and out, is covered with coarse granules (corticate granules) and small squamules, producing a distinctly pebbled, gritty look. It is not powdery-floury, and this is the key separator from several close relatives.

Apothecia and chemistry

Brown apothecia, when present, sit on short stalks around the cup rim, sometimes clustered. Colour is dull to dark brown, never red. The species usually reacts red with para-phenylenediamine (fumarprotocetraric acid) and negative to faintly yellow with potassium hydroxide.

Pixie Cups grow on thin acidic soil, mossy banks, ledges and crevices on rock outcrops, gravelly roadside cuts, old walls, sand dunes, peaty heath and well-rotted wood such as stumps and fallen logs. They tolerate a wide range of light levels but are commonest in open to lightly shaded, nutrient-poor sites where competing vegetation is sparse.

The species is very widely distributed across the northern hemisphere — throughout Europe, northern and temperate Asia, and North America from the arctic south into montane and lowland regions — with records much further afield. It is perennial and evergreen, present in all seasons, and grows slowly, with colonies persisting for many years on stable substrates. New cups form during moist periods in spring and autumn.

This lichen is a symbiosis in which the fungal partner builds the squamules, stalks and cups, and green algal cells beneath the surface supply carbohydrates through photosynthesis. Water and mineral nutrients are absorbed straight from rain and dew over the whole surface, allowing colonisation of bare mineral soil, rock crevices and decaying wood too poor for most plants.

As a pioneer it stabilises loose soil on banks and dune slacks, traps windblown dust and organic particles, and slowly builds a substrate for mosses and small vascular plants. Its acids weather mineral grains at a very slow rate. The cup itself functions as a splash-cup: raindrops striking the goblet fling out granules and soredia-like propagules, carrying both fungal and algal partners together to new ground, which is a more common route to new colonies than ascospores from the brown apothecia.

Cladonia fimbriata, the trumpet lichen, is the closest confusion: its cups flare more gradually from a longer, more slender stalk, and crucially its entire surface is coated in fine flour-like soredia rather than coarse granules, giving a smooth mealy appearance rather than a pebbled one. Cladonia chlorophaea is intermediate and granular-sorediate, and separating it from Cladonia pyxidata often needs chemical tests; as a rule pyxidata has coarser corticate granules and squamules on the podetium.

Cladonia coniocraea, the common powderhorn, tapers to a point and rarely forms a proper cup at all. Cladonia gracilis has tall, smooth, shiny brown-green podetia with narrow cups, quite unlike the squat grey-green goblets here. Cladonia cervicornis has cups that proliferate in tiers, one from the centre of another, forming a stack. Red-tipped relatives such as British Soldiers are excluded immediately by the scarlet apothecia; the Pixie Cup's fruiting bodies are always brown.