Pelargonium Webcap

Pelargonium Webcap (Cortinarius flexipes) is a small Telamonia webcap best known for its smell: crushed or freshly gathered fruitbodies release a sharp, green, unmistakable pelargonium-leaf odour, the same scent given off by bedding geraniums. In a genus where hundreds of small brown species look nearly identical, an odour that distinctive is a genuine gift.

Visually it is a dainty mushroom with a dark conical cap dusted in white veil fibrils, violaceous young gills and a slim, often slightly bent stem hooped with pale girdles. The violet fades quickly as rusty spores ripen, so a mixed-age troop shows the full colour sequence at once.

The species is treated broadly, with several varieties recognised — including plants once separated as C. paleaceus — and modern work shows the complex contains more than one taxon. In the field the working concept remains the same: a small frosted webcap of mossy northern woodland that smells strongly of geranium leaves.

Cap

Small, 1.5–4 cm across, conical or bell-shaped when young and expanding to convex with a sharp persistent umbo. The ground colour is dark chestnut- to date-brown when moist, drying pale ochre-brown, and the whole surface is coated with fine white to silvery fibrils and small appressed scales that are densest towards the margin.

Gills

Rather widely spaced, adnate, distinctly violaceous or lilac-grey in young fruitbodies before turning clay-brown and then rusty brown with maturity. The edges are minutely fringed and paler. A white cortina covers them in the button stage and leaves a rusty zone on the stem.

Stipe

Slender, 3–8 cm tall and only 2–6 mm thick, cylindrical and often noticeably flexuous or bent — the source of the epithet flexipes. It is violaceous at the apex when fresh, brownish below, and marked with one or several irregular whitish veil girdles. White mycelial threads bind the base to moss.

Flesh & spore print

The flesh is thin, brownish and hygrophanous, with a strong and persistent pelargonium-leaf smell that is the single most reliable field character. The spore print is rusty brown, and the spores are ellipsoid and warted.

Cortinarius flexipes occurs in damp, mossy woodland with birch, willow, spruce or pine, and is a frequent species of Sphagnum bogs, birch carr, damp heath and conifer plantation edges. It fruits directly from moss cushions and deep litter, usually in scattered troops rather than clumps, and favours acid, humus-rich soils.

The season runs from late summer through autumn. It is common and widespread across northern and central Europe, with a strongly boreal distribution, and comparable populations occur across northern North America in birch and spruce forest.

Like other webcaps it is an ectomycorrhizal symbiont, forming root sheaths on birch, willow and conifers. In the acid, waterlogged, nutrient-poor peaty soils where it is most at home, that partnership is central to tree nutrition, since much of the available nitrogen is locked in organic matter that the fungal hyphae, rather than the roots themselves, can access.

The volatile compounds responsible for the pelargonium smell are produced in the fruitbody tissue and may act in deterring or attracting invertebrates; whatever their function, they are stable enough to serve as a taxonomic character. The perennial mycelium persists in moss and peat layers and forms part of the dense underground fungal fabric of northern bog woodland.

Cortinarius hemitrichus is the closest visual match, sharing the small size, frosted dark cap and girdled stem, but its young gills are pale clay-brown rather than violaceous and it lacks the geranium odour. Cortinarius paleaceus is part of the same complex and differs in finer, more scurfy veil scales and a duller cap.

Cortinarius obtusus has a smoother, more strongly hygrophanous cap with a sharp umbo and no white frosting, while small Inocybe species can look similar but are radially fibrillose or splitting, produce a clay- to snuff-brown spore print, and never show violet gills. Galerina species in the same moss have smooth caps and often a membranous ring instead of a cortina.