What You Should Know
Polyporus durus is an inedible species of fungi in the genus Basidiomycota. It is pallid gray-brown at first, then chestnut, darker at the center, very thin. Often lob-sided and lobed. Shiny and leathery, white beneath. Stem 20 to 35 x 5 to 15mm, often black at the base. The pores on the underside are barely visible to the naked eye. Grows on dead, decaying wood of deciduous trees, usually large, fallen, and very decayed trunks
It was first described by Joachim Christian Timm, and given its simple Asian name by Hanns Kreisel in 1984.
Other names: Bay Polypore.
Polyporus durus Mushroom Identification
The upper surface of the cap of this occasional polypore is smooth, not zoned, and reddish-brown with a much darker center. Ranging from 5 to 20cm across when fully developed, but often lobed and irregular rather than round, the thin caps are slightly funneled and have wavy margins at maturity.
1-5cm long (although there is no clear delineation between cap and stem) and 0.5-1.5cm in diameter, the grayish stems are sometimes almost black at the base; tapering towards the base; usually connected eccentrically to the fertile underside of the cap.
Tubes and Pores
Beneath the cap, the tiny white tubes are packed together at a density of 5-8 per mm (not clearly visible to the naked eye, and hence a magnifying glass is a very useful accessory in the field); they are between 0.5 and 2.5mm deep and terminate in whitish pores that turn yellowish from the margin as they age. The tubes are decurrent with the stem.
Cylindrical or sausage-shaped, smooth, 5-9 x 3-4µm; inamyloid.
Odor and Taste
Odor is mushroomy but not distinctive; tastes mild.
Saprobic, occasionally on living hardwood trees but mostly on dead hardwood - often fallen branches, particularly of Beech.
New fruit bodies produce spores from late spring to autumn, but in dryish locations, these tough polypores often persist throughout the year.
Polyporus durus Look-Alikes
Is paler are has larger pores but smaller spores.
Has a fringed hairy margin.
Is much paler with radiating streaks on its surface. It is also found on dead/dying deciduous wood, but not on living trees.
Is very similar in appearance.
Polyporus durus Taxonomy and Etymology
The Bay Polypore was described scientifically in 1788 by Timmermans (no biographical details for this authority are known to us), who created its basionym when he gave it the scientific binomial name Boletus durus. (Three years later, in 1801, Christiaan Hendrik Persoon described the same polypore under the scientific name Polyporus badius.)
It was German mycologist Hans Kriesel (born 1931) who in 1984 transferred this species to the genus Polyporus and established its widely-accepted scientific name three years later, in 1801, as Polyporus durus.
The generic name Polyporus means 'having many pores', and fungi in this genus do indeed have tubes terminating in pores (usually very small and a lot of them) rather than gills or any other kind of hymenial surface.
The specific epithet durus is a Latin adjective meaning hard, tough or durable. (The synonymous epithet badius also comes from Latin and means bay brown.) The fruitbodies of this tough polypore are slow to rot. As a result, you can expect to find Bay Polypores all through summer, albeit with darkened pore surfaces and no longer producing spores.
Polyporus durus Synonyms
Melanopus picipes (Fr.) Pat. 1887
Leucoporus picipes (Fr.) Quél. 1886
Polyporellus picipes (Fr.) P. Karst. 1879
Polyporus dibaphus Berk. & M.A. Curtis 1872
Polyporus trachypus Berk. & Mont. 1856
Favolus trachypus Berk. & Mont. 1856
Polyporus picipes Fr. 1838
Boletus durus Timm 1788
Boletus perennis Batsch 1783