This fungus is commonly known as the birch polypore, from the growing on declining birch trees. Piptoporus betulinus is considered a parasite on living birch trees, but transitions to a saprophyte after the tree dies. Upon birch trees, you will find brown to grey spherical caps that are 10-25 cm in diameter and 2-6 cm thick at maturity (Figure 1 and 2).
Several of these caps can form on one trunk of one tree (Figure 3). The pores are densely packed with 3-4 every mm, and each pore is 1.5-5 mm deep, containing ellipsoid to cylindrical smooth 4-6 by 1.3-2 µm white spores (Figure 4). The pores release a white spore print. Generally, this fungus fruits in the late summer and early fall, but fruiting bodies can be found year round. The caps will dry down and can be used as a fire starter.
Piptoporus betulinus is a basidiomycete within the class: Agaricomycetes, order: Polyporales and family: Fomitopsidaceae. This species has many synonyms over the years since its discovery by carl Linnaeus in 1753 including Polyporus betulinus (Bull.) Fr., Boletus betulinus Bull., Boletus suberosus L., and Agarico-pulpa pseudoagaricon Paulet.
When fruiting bodies are immature or very young, they are considered edible, but are not reported to be of good taste.
In addition to being a flammable material when dried, the fruiting bodies are also known to produce piptamine an antibiotic. Interestingly, this fungus was found with a 5,000-year-old mummified body in the Alps between Austria and Italy, as a neck thong. Apparently humans have had an interest in P. betulinus for a very long time.
Capasso L. 1998. 5300 years ago, the ice man used natural laxatives and antibiotics. Lancet. 352: 1864.
O’Reilly P. 2011. Piptoporus betulinus (Bull.) P. Karst- Birch Polypore or Razor strop fungi in Fascinated by fungi http://www.first-nature.com/fungi/piptoporus-betulinus.php Access Nov 21, 2016.
Schlegel B, Luhmann U, Hartl A, Grafe U. 2000. Piptamin, a new antibiotic produced by Piptoporus betulinus Lu 9-1. Antiot 53: 973-974.12.02.16