365 Urban Species. #065: Birch Polypore

[urbpan]

photos by cottonmanifesto
Urban species #065: Birch polypore Piptoporus betulina

Twice before in this series (red tree brain and black knot) we have seen fungi that are specific about what trees they infect. Here we return to the theme with birch polypore ("polypore" refers to the many small holes that make up the spore-producing underside). Birch polypore is a mushroom produced by a fungus that only infects birch trees (one source claims that it occurs "rarely on beech"). It can infect living trees as a parasite, and when the tree sickens, whether due to the fungus or other cause, it will feed on the dead wood. Seldom will you encounter a dead birch tree without several birch polypore mushrooms on it.

The fungus is also called "razor strop," because apparently its flesh can be used to hone a blade. The dry spongy mushroom can also be used as tinder, and may have medicinal uses. The well-preserved 5000 year old corpse of a man found in the alps was found to have a couple pieces of birch polypore threaded on a cord, on his person. What value these specimens had to the man is a matter for speculation and contemplation.