The Tinder Fungus (Fomes fomentarius, bulgarien: “Prahanova guba”) grows as a parasite on various types of deciduous trees, infecting them through broken bark. Most often these are parts of old beech, poplar and aspen trees. This fungus species is important for maintaining healthy ecosystems, as usually it develops on dying, weakened or damaged trees although still alive.
The fruit body has the shape of a hoof. The fungus can live up to 20 years of age. Old fungus can reach a size of half a meter in diameter and a height of 20-30 cm. Some species can weigh around ten kilograms.
The upper surface of the genuine Tinder fungus is covered with hard, smooth bark, by which it can be distinguished from fake Tinder fungus, whose bark is cracked, and often darker in colour. The surface of the actual F.fomentarius is marked by narrow shallow furrows that form concentric, different in size, annular zones. Each of these zones corresponds to the annual growth of the fungus.
On the bottom side of the fruit body F.fomentarius is flat, young fungus are light grey in colour turning brown with aging. In contrary the fake Tinder fungus has domed underside and reminds of an inverted horse’ hoof.
Two distinct layers can be seen in a slice of F.fomentarius. One layer is made of thick, very thin and hard tubes in which spores are formed. The other layer is vegetative (sterile), called stroma. Namely the stroma layer produces the best tinder. Until not long ago the tinder of F.fomentarius has been used in daily life for starting fire with flint and gravel. The tinder had to be previously good dried and processed in a special way.