Wednesday, January 25, 2012

Birch Brackets

I found two typical bracket fungi that live on silver birches this afternoon, on some trees on the banks of the river Tyne near Wylam. This is the aptly named hoof fungus Fomes fomentarius. We tend to think of toadstools as here-today-gone-tomorrow organisms that appear overnight, shed their spores over a day or two and then wither away but bracket fungi like these are perennial, adding a new layer of spore- producing tissue (the hymenium) every season until the tree that they are digesting has yielded up all its available nutrients. During their long lifetime the brackets can produce millions of spores. Each successive layer of spore-producing tissue is marked on the surface of the bracket by a ring-like indentation, rather like the annual rings of a tree but visible on the fungal outer surface. The hymenium on the underside of this specimen, formed from thousands of pores lined with spores, shows signs of damage - probably from a slug.

These two are old specimens, are probably moribund - their hyphae have exhausted the supply of nutrients they can extract from their host's wood, which by this stage has developed a crumbly texture akin to balsa wood.

 This is an old specimen of the most familiar bracket fungus growing on birch, the birch polypore Piptoporus betulinus, also known as the razor strop fungus on account of its past use for honing a keen edge on cut-throat razors. Young specimens tend to be cream-coloured but they go brown and become leathery as they age. 

Bracket fungi like these are hosts to a variety of different insects that breed inside their tissues, so this is a food chain where plant tissue is being converted into fungal tissue which in turn is being transformed into animal tissue. If you harvest one of these old bracket fungi at this time of year and keep it in a container covered in muslin (which I've just done) you can expect to see a variety of different beetles emerge in spring and early summer - and if they do I'll post pictures of them when they appear.


  1. Replies
    1. Thanks! No wonder old birches are popular nest sites for woodpeckers Bob........