Birch polypore, Razorstrop bracket.
Other birch species.
Found growing at locations along the entire above-ground scaffold structure of the host tree. Abundant on dead trees, most notably.
Annual . Rubbery. Emerges from lenticel bands as an off-white mass. Mature fruiting bodies have a greyish-white to tan-brown upper surface and off-white pore surface that can tinge golden brown in post-maturity. Flesh white. Shallow tube layer 1-2mm deep. Desiccates to a mottled medium to dark grey – sometimes greenish.
Daedaleopsis confragosa (often growing on birch in similar locations – this fungus has maze-like pores and often blushed reddish brown).
Attributed to a cubical brown rot of the wood. Parasitic – at least, mildly. Exists as a vascular endophyte, prior to colonisation. Colonises when host tree becomes stressed. Presence therefore signals physiological stress and decline. Where targets exist, tree removal may be justifiable.