Trumpet Lichen

The Trumpet Lichen forms neat, slender goblets that widen gradually from a long stalk, so the profile really does suggest a small trumpet or champagne flute rather than the squat wine-cup of the pixie cups. It is one of the most frequently encountered Cladonia species in temperate regions, turning up on rotting stumps, mossy walls, peaty banks and roadside cuttings.

As in all Cladonia, the organism is built in two parts: a primary thallus of small leafy scales lying on the substrate, and upright secondary podetia rising from them. Here the podetia are unbranched, smoothly conical, and end in a shallow cup whose rim is often finely toothed or fringed — the source of the epithet fimbriata, meaning fringed.

The defining texture is the covering of soredia: minute powdery granules, each a bundle of algal cells wrapped in fungal threads, which coat the entire podetium in what looks like a dusting of pale flour. This mealy surface, combined with the slim gradual flare, separates it from the coarser, more granular cup lichens.

Primary thallus

Squamules at the base are small, 1–4 mm, grey-green above and white below, often shallowly lobed and sometimes largely hidden among moss. They can be sparse in older colonies where the podetia dominate.

Podetia and cups

Podetia are 10–30 mm tall and slender, 1–2 mm thick at the base, unbranched, and flare gradually and evenly into a shallow, regular cup 2–5 mm across at the top. The stalk is generally longer relative to the cup width than in the pixie cups, giving an elegant wine-glass or trumpet outline. Cups are hollow and often perforated at the centre of the base.

Surface

The entire podetium, from base to cup rim and often on the inner cup surface too, is covered in fine, farinose (flour-like) soredia, giving a matt, powdery, pale grey-green appearance with no visible granules or scales. Rubbing the surface leaves powder on the finger.

Rim, apothecia and chemistry

The cup rim is entire to finely toothed, sometimes bearing short marginal projections. Apothecia, when produced, are small and pale to dark brown, sitting on short stalks at the rim — never red. Potassium hydroxide is usually negative to weakly yellow; para-phenylenediamine gives a red reaction from fumarprotocetraric acid.

This lichen colonises acidic, nutrient-poor substrates: rotting stumps and logs, old wooden fence posts, peaty and sandy soil, mossy banks, heathland, dune grassland, the mortar and tops of old walls, and the bark at the bases of trees. It tolerates moderate shade better than many cup lichens and is often found in woodland margins and hedge banks as well as open heath.

It has a very broad distribution across Europe, Asia, North America, and further afield in temperate regions of both hemispheres, and is one of the commoner lichens in many settled landscapes because it tolerates a degree of disturbance. Perennial and evergreen, it is visible in every season, with new podetia produced during the damp growing periods of spring and autumn.

The Trumpet Lichen is a partnership between a fungus, which constructs the squamules and trumpet-shaped podetia, and green algal cells housed in a layer under the surface that photosynthesise for both. It absorbs water and dissolved nutrients directly from precipitation, which is why it flourishes on rotting wood and thin acidic soils where mineral nutrients are scarce.

It is a colonist and stabiliser of degraded substrates, helping to knit loose soil on banks and to bind the surface of decaying wood, and its slow breakdown adds organic matter to the developing soil profile. Its reproductive strategy is heavily weighted toward the soredia: these tiny composite propagules, containing both partners, are washed and blown away in large numbers and can establish immediately without needing to find a compatible alga, which explains the species' abundance and its rapid appearance on new stumps and banks. Ascospores from the brown apothecia provide an additional, less frequent route.

Cladonia pyxidata, the pixie cup, has squatter, more abruptly flaring goblets and a surface of coarse granules and small scales rather than fine powder — a lens shows pebbles instead of flour. Cladonia chlorophaea is very similar in outline but its soredia are coarser and more granular, and reliable separation often needs chemical spot tests or thin-layer chromatography.

Cladonia coniocraea, the common powderhorn, shares the fine soredial coating but tapers to a blunt point and only rarely produces a narrow cup, and its podetia are usually more curved and slender. Cladonia gracilis has taller, shiny, brown-tinged smooth podetia with narrow cups and no powdery coating. Cladonia macilenta also has sorediate podetia but bears bright red apothecia and generally forms no cup at all. In every case the two things to check are whether a true open goblet forms, and whether the surface is floury, granular or smooth.