Sometimes when you are out hiking, you see something that stops you in your tracks. Just off a path in the Peak District National Park, I saw a very strange symmetrical growth jutting out from the trunk of a Silver Birch (Betula pendula), that looked just like the hoof of a horse! On closer examination, it turned out to be that very strange fungus known as the Horse’s Hoof Fungus – or sometimes the Tinder Fungus (Fomes fomentarius). From prehistoric times, this fungus has been used as tinder to aid in fire starting. As you can see, this particular growth has cracked, and this has exposed a layer of the structure called amadou. After the fungus has been harvested, this layer can be stripped out, and then soaked in a solution of potassium nitrate. When dried out, and hammered flat, the amadou can be used to catch sparks struck between a flint and a piece of iron, and then used to light a fire. There exists evidence that Iron Age peoples exploited this same property by using sparks struck between flint and a piece of iron pyrites.
Amadou also has an amazing capacity to absorb water. When I was young, I used to go fishing a great deal, sometimes even fly-fishing on the River Derwent, in Derbyshire. I had been inspired by a wonderful book called, ‘Mr. Crabtree Goes Fishing: A Guide in Pictures to Fishing Round the Year’ by Bernard Venables (Mirror Features, 1950), and one of the many tips he demonstrated was the use of a piece of amadou to periodically absorb water from a dry fly (when fishing for trout) before slightly oiling it to keep it above the surface layer, like natural insects.
Horse’s Hoof Fungus is parasitic on the Silver Birch and is also sometimes seen infesting the European Beech (Fagus slyvatica). However, it is a general indicator of ill-health of the tree, whichever species it is found on. When the tree finally dies, the Horse’s Hoof will continue to feed off the now decaying wood, but will have to grow a new fungal body, parallel to the ground, so that its spores can propagate correctly. All in all, a most unusual fungus, with a couple of useful attributes!