Birch tinder (Fomitopsis betulina)
- Division: Basidiomycota (Basidiomycetes)
- Subdivision: Agaricomycotina (Agaricomycetes)
- Class: Agaricomycetes (Agaricomycetes)
- Subclass: Incertae sedis (of uncertain position)
- Order: Polyporales (Polypore)
- Family: Fomitopsidaceae (Fomitopsis)
- Genus: Fomitopsis (Fomitopsis)
- Type: Fomitopsis betulina (Trutovik birch)
- Piptoporus betulinus
- Pipptoporus birch
- birch sponge
Birch polypore, or Fomitopsis betulina, colloquially called birch sponge, is a wood-destroying fungus. Most often it grows singly or in small groups on dead, decaying birch wood, as well as on diseased and dying living birch trees. The fungus, which is located and develops inside the tree trunk, causes a rapidly developing reddish rot in the tree. Wood under the influence of tinder fungus is actively destroyed, turning into dust.
The sessile fruiting mushroom body does not have a stem and has a flattened reniform shape. Their diameter can be twenty centimeters.
The fruiting bodies of the fungus are annuals. They appear at the end of summer in the last stage of decay of the tree. During the year, overwintered dead tinder fungi can be observed on birch trees. The pulp of mushrooms has a pronounced mushroom smell.
The fungus is common in all places where a growing birch is observed. It does not occur on other trees.
Young white mushrooms become yellowish with growth and crack.
The birch tinder fungus is not suitable for consumption due to the bitter and hard pulp. There is evidence that its pulp can be consumed in a young form before acquiring stiffness.
From this type of fungus, drawing charcoal is made, and polyporenic acid, which has an anti-inflammatory medicinal effect, is also extracted. Often the pulp of the tinder fungus is used in folk medicine to treat various diseases. From young birch tinder fungi, various medicinal decoctions and tinctures are prepared with the addition of pure alcohol.