Hymenochaete rubiginosa  (Dicks.) Lév. - Oak Curtain Crust

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Polyporales - Family: Hymenochaetaceae

Hymenochaete rubiginosa, Oak Curtain Crust

Nearly always associated with dead oak trees, this easily-overlooked crust fungus varies considerably in its appearance, sometimes mainly resupinate beneath fallen logs but usually in bracket form when on dead stumps..

Distribution

Widespread in southern Britain and Ireland but scarce further north, Oak Curtain Crust is also fairly common throughout most of mainland Europe at least as far south as northern Italy.

Hymenochaete rubiginosa, Gloucestershire

The Oak Curtain Crust shown above were found on oak logs in southern England.

Taxonomic history

When, in 1785, Scottish botanist-mycologist James J Dickson (1738 - 1822) described Oak Curtain Crust fungus, he gave it the name Helvella rubiginosa. (Helvella fungi are ascomycetes, but the distinction was not clear in those pioneering days of fungal taxonomy. Dickson retains credit for the basionym, but the generally-accepted scientific name for this corticioid basidiomycete fungus is now Hymenochaete rubiginosa, this name having been given to it in 1846 by French mycologist Joseph-Henri Léveillé (1796 - 1870).

Synonyms of Hymenochaete rubiginosa include Helvella rubiginosa Dicks., Auricularia ferruginea Bull., Stereum ferrugineum (Bull.) Gray, Stereum rubiginosum (Dicks.) Gray, and Hymenochaete ferruginea (Bull.) Massee.

Etymology

Hymenochaete, the genus name, comes from hymen- a prefix referring to the fertile membrane (the crust surface), and -chaete perhaps from the Greek noun chaite meaning long hair and perhaps referring to the fine hairs (settae) on the upper surfaces of fungi in this generic group.

The specific epithet rubiginosa means rusty and refers to the reddish-brown colour of the hymenial (fertile) surface of this crust fungus.

Identification guide

Hymenochaete rubiginosa, closeup of infertile surface

Upper (infertile) surface

Perennial fruitbodies are irregularly oval with wavy margins; 2-4cm across and concentrically ridged on the upper surface, which feels finely velvety (it is covered in fine pointed hairs, visible with a good hand lens). the infertile surface is dark brown, except for the growing margin which is noticeably paler.

Sometimes the fruitbodies are largely resupinate, while on occasion they can form shelf-like brackets.

Hymenochaete rubiginosa, closeup of fertile surface

Lower (fertile) surface

The fertile surface is mainly smooth but often with a few scattered warty lumps or short warty ridges. Orange-brown when young, the fertile surface eventually darkens to a greyish red-brown. (The tough flesh of Oak Curtain Crust is also greyish brown.)

 

Spores

Ellipsoidal, smooth, 4.5-6 x 2.5-3μm; inamyloid.

Spore print

White.

Odour/taste

Not distinctive.

Habitat & Ecological role

On fallen timber of dead hardwood trees, nearly always oaks and most commonly appearing at an exposed surface where a fracture has occurred or the bark has fallen or rotted away.

Season

Perennial crusts and brackets persist throughout the year, but new young fruitbodies generally appear in early to mid summer and release their spores during late summer and autumn.

Similar species

Alder Bracket Inonotus radiatus produces paler fruitbodies and weeps honey-coloured droplets; as the common name implies it is is found mainly on the basal roots and lower trunks of alder trees.

Hymenochaete rubiginosa, Cambridgeshire, England

Culinary Notes

Oak Curtain Crust Hymenochaete rubiginosa is tough and leathery, and so it can have no culinary value.

Reference Sources

Mattheck, C., and Weber, K. Manual of Wood Decays in Trees. Arboricultural Association 2003.

Pat O'Reilly, Fascinated by Fungi, 2011.

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

BMS List of English Names for Fungi

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 and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Acknowledgements

Some of the pictures on this page are shown with the kind permission of Simon Harding.

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