Friday Fungus: a useful mushroom?

OK so the birch polypore (Piptoporus betulinus) is a parasite and kills birch trees which I suppose isn't all that friendly. But there's plenty of birches to go round and mostly it colonises older trees with bad hearts.

It is however a useful fungus - here, for example, is how to make a plaster from it. You can also dry the mushrooms and use them as firelighters and even to sharpen knives.

However, it isn't good eating (by which I mean you can eat it but it doesn't taste nice and is as tough as old boots).

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