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Foraging Diaries - Birch Polypore Fungus - Fomitopsis betulina

There a sometimes-killing-

but also useful - fungi

sprouts from a rot-set silver bough

I tell you - 'it is also known as

razor strop fungus -

due to its rough edges -

many lost uses - like fire carrying'

-Mike Bell

Family: Fomitopsidaceae

Botanical Description

Average Height: 6cm

Average Cap Width: 30cm

Season: August - November (UK)

Fruiting Body: Starts out globe like, as it emerges from the tree trunk then forming a hoof shape and eventually an enlarged flat bracket. White then turning grey/brown with age. The underneath pores are very fine and white in colour, turning buff with age. The flesh is white and firm. The spore print is white. They grow singly, but there are often several on the same host tree, so from a distance they look like a series of steps

Habitat: Found growing on dead or damaged birch trees

Harvest time: From September onward until January, as soon as the fruiting body is fully grown (Harvest sustainably and leave enough to distribute spores for growth the following year)

Flavour: Bitter, mushroomy taste

Also known as Razor Strop Fungus and Birch Bracket, the Birch Polypore is a parasite to Birch Trees slowly and then living on dead trees for many years until the Birch has rotted away.

When it comes to foraging a good rule of thumb to abide by:

If in doubt, leave it out

Birch Polypore is the Swiss Army Knife of fungi, it has many different uses and a long tradition of being applied in folk medicine, humans have been using Birch Polypore for a long time, the earliest evidence of their use dates back to over 5,000 years ago.

The ancient body of a herder buried in ice, high in the Tyrol region of the Austrian Alps was unearthed in 1991, a 5300 year old mummy that they named Otzi, with all his possessions perfectly preserved. He was carrying Birch Polypore on a leather lace around his neck, they found he had a parasitic internal worm for which one of the cures was polyporenic acid, one of the chemicals present in Birch Polypore.

The name Razor Strop Fungus comes from the ability to use the fungus to sharpen razors or knives on its tough leathery flesh. It has also been used to carry fire, by transporting embers from one place to another. Once it has begun to smolder, it is relatively difficult to extinguish and will burn for a long time if kept from getting wet.

Birch Polypore has many medicinal properties, and continues to be studied by scientists. Cancer is one of the UK's most common diseases - and biggest killer. Birch Polypore has been shown to support cancer treatment in several ways:

- The betulinic acid found in Birch Polypore selectively causes the death of cancer cells without appearing to harm healthy cells

- Birch Polypore hinders the formation of new blood cells which occur in tumor growth and also slows cancer cell proliferation

- If individuals are undergoing treatment for cancer, such as chemotherapy which can leave their immune systems shattered, Birch Polypore's immune stimulating action helps to counter these effects.

Pharmacological studies have shown Birch Polypore to be anti-parasitic, anti-bacterial, anti-viral, anti-inflammatory, anti-cancer, neuroprotective and immune-boosting. Those properties combined with its spongy texture make it an excellent field bandage, a DIY plaster can be made from the underside of the mushroom, a strip needs to be cut and carefully removed from the pore membrane. This provides a microporus, anti fungal, antiseptic and self sticking plaster. A corn or blister plaster can be easily fashioned from the flesh of the mushroom by cutting some flesh into a doughnut shape of the right size and applying to the corn or blister.


Growing exclusively on Birch, it is difficult to confuse with any other fungus if know how to identify a Birch Tree. As with any new food you are introducing to your diet, try a little at first to make sure there is no adverse reaction.

Birch Polypore Preparations

To take full advantage of the numerous medicinal health benefits, Birch Polypore can be dehyrated/dried and made into a decoction otherwise known as a simmered herbal tea. It has a rather bitter taste but can be sweetened with peppermint or honey, I quite like it as it is, slightly mushroomy but a little bitter. Due to the leathery texture and somewhat bitter flavour it is less than ideal to eat fresh.

Preparation Time

Around 6-8 hours, mainly consisting of dehydrating time.


1 Large Birch Polypore

Method The Birch Polypore is quite leathery, you will need to have a sharp knife to cut it and it can be difficult. You really want to prepare it no later than two days after harvesting, as it will become to tough to process.

Remove the dirt with a mushroom brush or vegetable scrubber

Cut the Birch Polypore into long thin slices, or small chunks. At this point, you can use the mushrooms right away or dry them for later use.

To dry, lay out on baking parchment on an oven tray, or use a dehydrator. I used the dehydrate setting on my air-fryer

Oven dry on the lowest setting, or put in the dehydrator. They can also be left on a warm window ledge to dry for a few days

They are ready when they lose their pliability and snap easily when bent

After letting them air out a bit to remove any possibility for condensation build-up, store the dehydrated mushroom slices in glass jars or another airtight container.Dehydrated mushrooms can be stored almost indefinitely

Making mushroom tea is a good way to extract the flavour and nutrients from tough, woody or rubbery mushrooms like Birch Polypore

Once they have been cleaned and prepared, you’ll want to simmer them in hot water to release the medicinal properties. This can be done with either fresh or dried Birch Polypore. Bring water to a boil and then reduce to a very slow simmer before adding your Birch Polypore.

Let the mushroom slow simmer for at least an hour, you don't want to boil as this will reduce the medicinal properties

Drink your Birch Polypore tea right away or save it for later use

Birch Polypore tea can be kept in the fridge for a few days or frozen into ice cubes. Add the liquid or ice cubes to soup or stews to enhance the medicinal value of your meals while masking the bitter flavour.

You can also use a Pestle and Morter to crush down the dried Birch Polypore, and then put it through a grinder to create a fine powder, which can also be added to food.

On a final note for fans of The Moomins, has anyone ever noticed The Groke has a nose which I am convinced is a Birch Polypore? Just me..?


Sinclair, L & Holohan, C (2021) Scotlands Wild Medicine Accessed 25/01/2023

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