betulina (Birch Polypore, Razor Strop Fungus) — Species | WeMush Taxonomy

betulina

Birch Polypore, Razor Strop Fungus

Fomitopsis betulina, formerly known as Piptoporus betulinus, is a common annual polypore fungus that grows almost exclusively on species of birch (Betula). It is a necrotrophic parasite, meaning it infects living trees—often causing stem breakage—and continues to degrade the wood as a saprotroph after the tree dies. The fungus causes a brown rot, degrading cellulose and hemicellulose while leaving the lignin structurally altered but intact, resulting in a cubical cracking pattern in the wood. The fruit bodies are bracket-like, kidney-shaped to semicircular, and broadly attached to the substrate. Young specimens are rubbery and firm, becoming corky and light in weight as they mature and dry. The upper surface is covered by a smooth, thin, paper-like skin (pellicle) that ranges from pale grayish-brown to tan and often peels away in age. The pore surface is initially white, turning yellowish or brownish with age. Historically significant, this species was found carried by 'Ötzi the Iceman' (3300 BCE), suggesting thousands of years of human medicinal use.

Edibility: Medicinal only. The flesh is tough, corky, and rubbery, rendering it inedible in a culinary sense. It has a distinctly bitter and acidic taste. It is primarily used for medicinal preparations, such as teas, tinctures, or dried powders. Historically, the flesh was also used as a styptic to stop bleeding and as a strop for sharpening razors (hence the name 'Razor Strop Fungus'). Safety: While non-toxic, the tough texture presents a choking hazard if consumed whole. As with all medicinal mushrooms, extracts should be used with caution by those on medication, particularly blood thinners, due to potential anticoagulant properties.

Habitat: Temperate hardwood forests, heathlands, and boreal forests where birch trees are present. It is strictly associated with birch stands.. Substrates: Betula pendula (Silver Birch), Betula pubescens (Downy Birch), Betula papyrifera (Paper Birch), Dead or dying standing trunks, Fallen birch branches. Conditions: Thrives in cool, temperate climates with high humidity. It is a brown-rot fungus that requires the specific hemicellulose composition of birch wood.. Season: Fruit bodies typically emerge in late summer to autumn (August to November) but are tough and persistent, often remaining on the tree through winter and into the following spring.

Difficulty: INTERMEDIATE

Growth: moderate

Contam Risk: medium

Cultivation Suitability

Preferred Substrates

Birch sawdust fortified with bran

Birch logs (plug spawn)

Birch dowels

Distribution

Native: North America (Northern US and Canada), Europe (Widespread), Asia (Siberia, Northern China, Japan). Introduced: Rarely introduced outside native birch ranges. Circumboreal; very common and widespread throughout the Northern Hemisphere wherever Betula species occur.

Known Strains (0)

No strains cataloged yet for this species.

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