This time last year I was visiting my parents back in the UK, after not seeing them for a year and a half due to the pandemic. How time flies! They are very lucky to live near the beautifully sprawling Sherwood Forest in Nottinghamshire, lots of different areas, it’s a mine of experiences, biodiversity and incredible to see. We visited the historical Major Oak trail near Edwinstowe on one occasion and it was abundant in Birch polypores – Piptoporus betulina or Polyporus betulina or Fomitopsis betulina, the latter, apparently being the most accepted scientific name since 2016 according to the trusty website First Nature. Enough about confusing names as I look through my ID books and realise I should get some updated ones.
The birch polypore, is fascinating, ball-like when young, emerging from birch trees, it is a parasitical fungus. Many specimens I saw on this trip were young, I kept hoping that they Reticularia lycoperdon (aka Moon Poo), a slime mould, even though it’s not the season, I just really wanted to see some. It remains on my wish list. I kept prodding each one to check, but they were all too firm and indicated birch polypore.
After its globular growth, it then flattens and grows commonly into a kidney shape, retaining a narrow point of attachment to its poor host tree. The top side turns brown-ish or grey with some rings and often has a cracked appearance, there is a white margin that turns under when mature. The underside is said to have small white pores that mature grey. They fruit all year round, so a good one to keep an eye out for in all seasons, on living trees and dead wood.
I learned, after being surrounded by them, that birch polypore are said to be medicinal, used in folk medicine and was even found with a 5300 year old mummy in Austria. A scientific study from 2018, showed that it had particular immune system enhancing properties. One of its common names – Razorstrop fungus – belies another of its uses, that of a tool for sharpening razors on this hard fungus. It’s also known to be used to start campfires too.
This parasite is a brown rot, instead of white rots that break down lignin, brown rot attacks carbohydrates and demethylates the lignin, not being able to fully decompose it like white rot fungi.
A prolific fungus with a strong sociological and medicinal history which continues to evolve, birch polypore is now one of my favourites to look out for.
Basic Profile
Scientific name: Fomitopsis betulina formerly Polyporus betulina / Piptoporus betulina
Common English names: Birch polypore; Razorstrop fungus
Size of fruiting body: 8-30cm across , 2-6cm thick
Spores: 5-7 x 1.5- 2 µm
Gills: Pores, creamy white, angular, aging grey/brown
Edibility: Bitter taste, inedible unless processed
Lookalikes: Fomes fomentarius also on birch but much thicker and darker, like a horse’s hoof
On the Red Data List (extinct/critically endangered/endangered/vulnerable/near threatened):
References:
Brown Rot Fungi, Science Direct
Cate2 Database, managed and maintained by The Fungus Conservation Trust
Collins Complete Guide to British Mushrooms & Toadstools, Paul Sterry & Barry Hughes, 2009
National Biodiversity Data Centre
http://iucn.ekoo.se/, The Global Fungal Red List Initiative
Mushrooms and Toadstools of Britain and Europe, Edmund Garnweidner, 1994
Mushrooms, Patrick Hardy, 2013
Red Data List, British Mycological Society
The Encyclopedia of Fungi of Britain and Europe, Michael Jordan, 2004
Mushroomination 