Pearly Webcap

The Pearly Webcap is one of the pale lilac webcaps, a handsome mushroom whose dry, silky cap has a distinctly pearly sheen and a faint violet wash that fades to buff as the fruitbody dries. It sits in the group of webcaps sometimes gathered as Sericeocybe, defined by dry, silky-fibrillose, non-hygrophanous caps and a well-developed silky outer veil that sheathes the stipe.

Within Cortinarius, violet-tinted species are numerous and notoriously difficult, but this one is among the more tractable, being a broadleaf-woodland species with a whitish-violet rather than deep violet colouring, a club-shaped stipe and no strong smell. The violet tones are strongest in young buttons and in the gills and the apex of the stipe.

It is a common autumn fungus of oak, beech and birch woodland across the temperate northern hemisphere, and its pale silvery form is easy to pick out against dark leaf litter.

Cap

4-8 cm across, at first hemispherical, then convex and finally flattened with a broad low umbo. The surface is dry and silky-fibrillose with a soft pearly or silvery sheen, coloured pale silvery-violet to whitish-lilac, ageing and drying to pale buff or ochre-cream, especially at the disc. The margin is often incurved for a long time and may carry fine whitish veil fibres.

Gills

Adnate to slightly emarginate, moderately crowded and fairly broad, pale greyish-violet to lavender when young, then clay-brown and finally rusty brown as spores mature. The edges remain paler and slightly uneven.

Stipe

5-9 cm long, firm, distinctly club-shaped or swollen toward the base, whitish with a violet flush that is strongest at the apex. A silky white outer veil sheathes the lower stipe and often ends in a vague ring-like zone or one or two faint bands, above which the cobwebby cortina leaves rust-dusted fibres.

Flesh & spore print

Flesh is firm and whitish, tinged pale violet in the cap and stipe apex, unchanging when cut, and the smell is faint and unremarkable. The spore print is rusty brown; spores are almond-shaped and warted.

This webcap grows in broadleaved and mixed woodland, forming its partnerships mainly with oak, beech, birch and hazel, on acid to neutral soils. It fruits singly, scattered or in small groups in leaf litter, and is common on woodland banks and in the dappled shade of mature stands. It occasionally appears in mixed woods where conifers are present, but the pure conifer habitat belongs to its lilac relatives.

The season runs from late summer through autumn. It is widespread and frequent across Britain, Ireland and continental Europe, and is recorded across temperate North America in comparable broadleaf woodland.

Cortinarius alboviolaceus is ectomycorrhizal. Its mycelium colonises the short roots of oak, beech and birch, forming a fungal mantle and an inward-growing Hartig net that mediates the exchange of soil nutrients for tree sugars. In return for carbohydrates, the fungus supplies nitrogen and phosphorus captured from leaf litter and mineral soil across a far greater volume than the roots alone could reach.

The fungal network is perennial and can be extensive under a single mature tree, linking roots of several individuals. Fruiting is seasonal and moisture-driven, concentrated in the cool wet weeks of autumn, and the fruitbodies release rusty spores that drift into the litter to found new colonies on receptive rootlets.

Cortinarius traganus is a similar lilac colour but is a conifer species with a stouter bulbous stipe, ochre-saffron marbled flesh and a strong penetrating smell. Cortinarius camphoratus, also of conifer woods, has bluish-lilac young gills, whitish-lilac flesh and a strong smell.

Cortinarius malachius is another conifer species, with a more scaly-fibrillose cap and a less pearly sheen. Cortinarius anomalus overlaps in broadleaf habitat but has a browner, greyer cap and distinct ochre-yellow veil bands on a more slender stipe rather than the silky whitish sheath seen here.