Birch Polypore – Fomitopsis betulina

Fungi of the Week

10th April 2020 | Info

Common name: Birch Polypore/ Razor Strop Fungus  

Scientific name: Fomitopsis betulina (previously known as Piptoporus betulinus 

Introduction: The Birch Polypore (Fomitopsis betulina) is an annually forming, large polypore bracket fungus that is native to the UK. They are relatively short-lived but can be both parasitic and saprobic.  


Cap: When young, the caps of the fruiting body of the birch polypore are typically spherical to subglobose in shape and a grey-brown colour. As they then begin to mature, they develop into more of a hoof-like form, before ultimately flattening out to an enlarged bracket which is brown on top and has a white underside. Younger caps are also typically smoother due to the fungus cracking as it matures. 

Tubes/Pores: Birch Polypores have densely packed small white tubes that end in very fine white pores. As the fungus matures, these white pores then turn buff.   

Spores: Cylindrical to Ellipsoidal in shape, the spores of a Birch Polypore have a white spore print.   

Flesh: The Flesh of a Birch Polypore is white has a soft texture which then becomes corky and firm as the fruiting body matures. 


Nearly always, the Birch Polypore forms on dead or dying Birch trees. They typically form as singular fruiting bodies, but you will often find that there are several fruiting bodies on one tree.  

Impact on Trees

Typically, the Birch polypore mainly affects principal branches and main stems on host trees. They are parasitic while the host tree is leaving and turn saprobic once the host tree has died and completely rots away. In the instance that a Birch tree has been previously damaged or is unhealthy, then the Birch polypore can rapidly cause brown rot decay to form, which ultimately leads to stems snapping. The fungus is also commonly associated with wounds or certain dieback that has been created by other factors.    

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