About this fungus
Frosty Webcap is a fungus in the Cortinariaceae family. Its habitat and field characteristics are summarised below.
A small brown woodland webcap whose young cap is dusted with fine white fibres, creating the frosted appearance behind its name. The coating thins with age and weather, leaving older mushrooms much plainer and harder to recognise.
What to check
Young fruit bodies may show a cobweb-like cortina between cap and stem. Look for white woolly scales or broken bands on the stem, pale buff gills that mature brown, and a rusty-brown spore print. There is no persistent ring and no volva. The frosted cap alone is not enough for a reliable species identification.
Variation
The hygrophanous cap is darker chestnut-brown when moist and becomes paler grey-brown as it dries. White fibres are densest on young caps and can be lost almost completely. The stem may retain pale fibrous zones after the cortina disappears.
Lookalikes
Many small brown Cortinarius species share a rusty print and temporary cortina. Close identification may require spore measurements and regional specialist knowledge. The genus includes seriously poisonous species, but the checked sources do not establish orellanine or deadly poisoning for Cortinarius hemitrichus itself.
Habitat and range
Ectomycorrhizal on soil and litter in damp woodland, often reported with birch and other broad-leaved trees, and sometimes recorded on shaded woodchip where tree roots are nearby. The best-documented concept is European, so records elsewhere need regional taxonomic care.
Food safety
Inedible.
Photographs
Thomas Pruß / CC BY-SA 3.0