Trumpet Lichen Identification Guide

First impression and where you are kneeling

Trumpet Lichen is a get down on your knees species. You find it on the flat top of a rotting conifer stump, along a weathered fence rail, on a peaty bank at the edge of heathland, on mortar of an old wall, on sandy disturbed soil, or around the mossy base of a birch. What catches the eye is a scatter of small pale grey green goblets, 5 to 25 mm tall, standing up out of a crust of tiny scales like a set of doll sized wine glasses.

The genus is easy. Cladonia lichens have a two part construction that no other common group repeats in quite the same way, and once you have the two parts in view you are three quarters of the way to a name. The species then hinges on a texture question that must be answered with a hand lens, not with the naked eye.

The two part structure

The first part is the primary thallus: a mat of small basal squamules, individual scales 2 to 5 mm long, greyish green above and chalky white beneath, often with crenate or shallowly lobed edges and frequently curling up at the tips to show the white underside. In this species those squamules usually persist and form a continuous crust around the stalks, although in shaded or crowded colonies they can be sparse.

The second part is the podetium: a hollow, upright stalk that grows from the primary thallus and, in this species, flares smoothly at the top into a regular cup or scyphus. Look at the profile. The stalk is slender and comparatively long, and it widens gradually into the cup so that the whole silhouette is a narrow trumpet or a champagne flute rather than a squat goblet. Cup mouths are commonly 2 to 5 mm across, and the rim is even and entire.

The texture that decides the species

Here is the character that matters most. Run a lens over the outside of the stalk and the inside and outside of the cup. In Trumpet Lichen the entire podetium is uniformly clothed in farinose soredia, that is, extremely fine, flour like granules, so even and so minute that the surface looks dusted rather than granular. Brush it with a fingertip and powder comes away. There should be no obvious patches of smooth green corticate surface except sometimes at the very base of the stalk.

Compare that with the coarsely granular soredia of the closely related cup lichens, where individual granules are large enough to see as separate grains and give the surface a rough, sugary, almost warty feel. That distinction, fine flour versus coarse sugar, is the working separation in the field, and it is why a hand lens of at least ten times magnification is essential for this group.

Cups, apothecia and reproduction

The cups themselves are regular and symmetrical, opening cleanly and rarely proliferating. Occasionally a second tier of small cups grows from the rim of the first, but tiered proliferation from the centre of the cup floor is not the normal habit here.

On the cup margins you may find tiny dark brown pycnidia, flask shaped structures that release asexual spores, and rather less often small dark brown apothecia on short outgrowths from the rim. Both are worth looking for but neither is needed for identification, because the species reproduces overwhelmingly by soredia. Each of those flour like grains contains fungal threads wrapped around algal cells and can begin a new thallus wherever it lands.

There is no spore print to take. Lichens release their ascospores gradually from apothecia rather than dropping a visible deposit, so the mushroom technique has no equivalent here. If apothecia are present and you want to go further, a thin razor section mounted in water will show colourless, simple, ellipsoid spores in eight spored asci. In practice the field identification rests entirely on growth form and surface texture.

Chemistry as a supporting test

Spot tests help place the species in a group even though they do not finish the job. The medulla of Trumpet Lichen contains fumarprotocetraric acid, so a drop of para phenylenediamine solution on the podetium turns red, while potassium hydroxide gives no reaction and the thallus does not fluoresce under ultraviolet light. That result is shared with several relatives in the same complex, so treat it as confirmation of the group rather than proof of the species, and go back to the fineness of the soredia and the slenderness of the stalk for the final call.

Substrate, conditions and season

This is a lichen of acid, nutrient poor, often disturbed substrates. Rotting stumps and fallen logs in the late stages of decay are classic, along with old fence posts and rails, the mossy bases of trees, peat and sandy heath soil, banks cut by paths, and the tops of old walls where a skin of moss and grit has built up. It is a pioneer, arriving early on newly exposed acid ground and then being crowded out as vegetation closes in.

Being perennial and slow growing it is present all year, though the podetia look freshest and greenest after rain and can bleach almost white during prolonged drought. It tolerates moderate levels of air pollution better than many lichens, so it persists in suburban and semi industrial settings where showier species have gone.

Separating the closest look-alikes

The Cladonia chlorophaea group is the main confusion. Those cups are usually broader, shorter stalked and flare more abruptly, and crucially their surface is covered in coarse granular soredia that a lens resolves into separate grains rather than an even dusting.

Cladonia pyxidata has broad, squat cups whose surfaces bear green corticate granules and small squamules rather than true soredia, giving a warty rather than powdery finish, and it favours soil and mossy rock.

Cladonia coniocraea grows in exactly the same places on rotting stumps and is also farinose sorediate, but its podetia taper to a point or open at most into a tiny rudimentary cup. Ask a simple question of each stalk: is there a genuine flared cup with a rim, or just a narrow tip? That single question separates them.

Cladonia ochrochlora resembles coniocraea but retains patches of smooth green cortex over the lower part of the podetium, with soredia confined to the upper section, and its cups when formed are narrow and irregular.

Cladonia cervicornis subsp. verticillata builds tiers of cups growing one out of the centre of another, giving a stacked, candelabra like structure, and its podetia carry squamules rather than fine powder.

Cladonia carneola has a paler, faintly yellowish tinge, sorediate cups, and fluoresces under ultraviolet light.

Cladonia gracilis is taller, brown tinged and largely corticate, with a smooth or scaly rather than powdery surface, so it feels quite different under the lens.

Finally, Cladonia polydactyla forms cups that are irregularly toothed and often bear red pycnidia and apothecia on the rim, a splash of colour that Trumpet Lichen never shows.