Polyporus umbellatus (Pers.) Fr. - Umbrella Polypore

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

Polyporus umbellatus

Much less common than the related species Grifola frondosa, which is known as Hen of the Woods, the fruitbodies of the Umbrella Polypore Polyporus umbellatus are fairly short-lived; they occur as fungal rosettes at the bases or on large underground roots of deciduous hardwood trees, and most often on oaks.

This fungus is parasitic and attacks living trees, causing a white rot. Trees can live for several years with this fungal infection, and so fruitbodies may recur for a number of seasons.

The Umbrella Polypore shown above was found in Bedfordshire, England.

Distribution

Rare in Britain, where it is mainly confined to southern England, this large and distinctive polypore occurs also in parts of mainland Europe and in many regions of North America.

Taxonomic history

In 1801 Christiaan Hendrik Persoon described this massive polypore, giving it the binomial scientific name Boletus umbellatus. In his Systema Mycologicum of 1821 the great Swedish mycologist Elias Magnus Fries transferred this species to the genus Polyporus, thereby establishing its currently-accepted scientific name Polyporus umbellatus.

Synonyms of Polyporus umbellatus include Boletus umbellatus Pers.Sclerotium giganteum Rostr., Grifola umbellata (Pers.) Pilát, and Dendropolyporus umbellatus (Pers.) Jülich

Etymology

The specific epithet umbellatus may be interpreted as 'having umbrellas', but another slightly different interpretation that more closely matches the shape of the branch tips is 'having a central depression - an umbilicus, like a navel'.

Identification guide

Fertile surface of Grifola umbellata

Fruitbody

The whole fruitbody can be up to 50cm in diameter; it comprises a thick fleshy basal stem that branches repeatedly with terminal branches ending in shallowly-funnelled caps with thin, wavy margins.

Caps

The individual caps are initially greyish brown covered in fine fibrils or small fibrous scales. The caps, which have white flesh when young, turn ochre and then brown as they age.

Pores of Grifola umbellata

Tubes and Pores

The fertile undersurface of the cap comprises shallow tubes typically 1 to 1.5mm deep and usually rounded; they terminate in pale cream angular pores spaced at typically 1 per mm and decurrent to the stem.

 

Spores

Cylindrical, smooth, 7.5-10 x 3-3.5μm; inamyloid.

Spore print

White.

Odour/taste

Pleasant sweet odour when young; less so when decaying. The taste is initially sweet, ultimately becoming acrid when the fruitbody is fully grown and begins to decay.

Habitat & Ecological role

Parasitic, at the bases of oak trees and other hardwoods. This fungus may also feed for some time as a saprobe after its host tree has died.

Season

Summer and autumn. The fruitbodies decay rapidly and do not persist through the winter.

Similar species

Grifola frondosa, Hen of the Woods, is more common; its fruitbody has terminal branches that end in fan-shaped or leaf-like fronds rather than rounded umbels.

The Umbrella Polypore could possibly also be confused with the much paler Wood Cauliflower Sparasis crispa, but that species grows only at the bases of conifers and most frequently Scots Pines.

Meripilus giganteus often forms rosettes at tree bases or from underground roots, but its fronds are much thicker and its main host is Beech.

Culinary Notes

Although it is an edible fungus, this polypore it is so rare that it should not be collected for eating.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

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

Acknowledgements

This page includes pictures kindly contributed by Hugh Purvis.

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