Cortinarius hemitrichus (Pers.) Fr. - Frosty Webcap

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Cortinariaceae

Cortinarius hemitrichus - Frosty Webcap

Cortinarius hemitrichus is one of the first webcaps to appear. From April through to November you can find this webcap fungus under deciduous trees and occasionally in damp areas on wood-chip paths. Unfortunately this is not one of the most common of webcaps, but its attractive 'frosted' appearance makes it very distinctive; once you have seen one you will immediately remember its name as the Frosty Webcap when you see others. Its lookalike, Cortinarius flexipes is distinguished by a strong odour of pelargonium.

Cortinarius hemitrichus - Frosty Webcap, mature specimens


An occasional species in Britain and Ireland, the Frosty Webcap is found throughout much of mainland Europe and in parts of North America.

Cortinarius hemitrichus - Frosty Webcap, young specimens

Taxonomic history

When in 1801 Christiaan Hendrik Persoon desdcribed this webcap he gave it the scientific name Agaricus hemitrichus. (Vast numbers of gilled fungi were dumped into the Agaricus genus in the early days of fungal taxonomy; most have since been moved to other genera leaving in the present-day Agaricus genus a much smaller number of gilled mushrooms that are sometimes referred to as the 'true mushrooms'.)

It was the great Swedish mycologist Elias Magnus Fries who, in 1838, transferred this species to the genus Cortinarius, whereupon it assumed its currently-accepted scientific name Cortinarius hemitrichus.

Agaricus hemitrichus Pers., is a synonym of Cortinarius hemitrichus.

Cortinarius hemitrichus - Frosty Webcap, Devon UK


The generic name Cortinarius is a reference to the partial veil or cortina (meaning a curtain) that covers the gills when caps are immature. In the genus Cortinarius most species produce partial veils in the form of a fine web of radial fibres connecting the stem to the rim of the cap rather than a solid membrane.

The specific epithet hemitrichus may come from the prefix hemi- meaning half and -trichus meaning hairy (or fibrous). If you believe that this is an incorrect interpretation we would appreciate your help to correct it.


This mushroom is generally regarded as inedible and it should not be gathered for eating. Some Cortinarius species contain the toxin orellanine, which if eaten destroys human kidneys and liver.

Identification guide

Cap of Cortinarius hemitrichus


Young caps are bell shaped and fawn, and they are liberally covered with white fibrils.

Mature caps, which often have distinctly pointed tops, are much paler and are typically 2 to 5cm in diameter. The white flaky fibrils soon fall off if handled.

Gills of Cortinarius hemitrichus


Initially pale buff and turning brown as the spores mature, the gills are adnate and crowded.

Stem of Cortinarius hemitrichus


Scurfy, brown-grey with white fibrous scales forming paler zones; often (as seen on the left) there is a distinct white woolly ring; 3 to 5mm diameter and up to 7cm tall. The base is slightly bulbous.

Spores, Cortinarius hemitrichus


Ellipsoidal, 7-9 x 4-5µm, with warty ornamentation.

Show larger image

Spore print

Rusty brown.


Not distinctive.

Habitat & Ecological role

Mycorrhizal, in deciduous woodland; also on well-shaded and damp wood chip paths under trees.


May to November in Britain and Ireland.

Similar Species

Cortinarius flexipes, the Pelargonium Waxcap, is similar but is distinguished by its strong odour of pelargoniums (house plant 'geraniums'!)

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

Fungi of Switzerland Agarics, part 3: Cortinariaceae, Breitenbach, J., Kränzlin, F.

British Mycological Society, English Names for Fungi.

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.

Cortinarius hemitrichus - Frosty Webcap, mature specimen, southern England


This page includes pictures kindly contributed by Simon Harding.

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