Piptoporus betulinus - Birch Polypore or Razor Strop Fungus

Taxonomy

Phylum: Basidiomycota

Class: Agaricomycetes

Order: Polyporales

This large polypore develops from a small white spherical swelling on the side of dead or living birch trees.

Barbers used to 'strop' or sharpen their cut-throat razors on the tough, leathery surfaces of these polypores, and so they became known as the Razor Strop Fungus.

This is a very tough, bitter fungus. Although young specimens are reportedly edible they are of poor quality and are not worth collecting.

Identification Guide

	Cap This very common polypore is grey-brown at first and almost spherical, flattening and turning browner on top and white underneath as it matures. 10 to 25cm in diameter and 2 to 6cm thick, the fruiting bodies arise singly but there are often several on the same host tree.
	Tubes and Pores The small white tubes are packed together at a density of 3 or 4 per mm; they are between 1.5 and 5mm deep and terminate in white pores that turn buff as they age.
Spore print	White.
Odour/taste	Bitter tasting, these polypores have a faint but not unpleasant taste.
Habitat	Restricted to dead or dying birch trees.
Season	Although you may see these bracket fungi persisting throughout the year, they are annuals and release spores in late summer and autumn.
Occurrence	Very common.
Similar species	Although mature specimens are shaped very much like the Dryad's Saddle fungus, Polyporus squamosus, it is difficult to confuse this polypore with any other species because of its distinctive colouring and specific restriction to birch trunks.