Fomes excavatus

February 27, 2023

Good evening, friends,
This week’s mushroom goes by a variety of common names: the tinder conk, the hoof fungus, and the ice man fungus to name just a few. This mushroom also has a couple different latin names as well – it used to be all classified under Fomes fomentarius but now the North American species is increasingly recognized as Fomes excavatus. I found this species last week in New Hampshire, but it’s one of if not the most common winter polypores. Getting to know this conspicuous mushroom will be useful for not only just winter hikes, but potential fire starting scenarios and quite possibly the future of plastic. Let’s dig in.

Fun Facts
This mushroom is the second of two mushrooms (the other the birch polypore) that was found on Ötzi the ice man – the oldest known natural mummy found frozen in the Alps and clocking in at approx. 5,300 years old. It is suspected that he was using the tinder conk for, you guessed it, tinder while he used the birch polypore as a topical antibiotic for his arrow wound or a purgative for his intestinal worms. The fibrous, brown, and spongy inner layer of the tinder conk – referred to as amadou – has long been used for tinder but can also be used for making hats, fly fishing ties, and other practical outdoor equipment.

It appears as if we’ve just scratched the rough, chitinous surface of the practicality of this common winter polypore. Just this past Wednesday, a study was published in Science Advances that highlighted the potential for F. fomentarius to be used to create “high-performance ultralightweight materials” (aka an alternative to plastic). The image below details the different structural components of the mushroom and shows how the “synergistic interplay” of the fungus’s mycelium creates three structurally and chemically distinct layers. It’s invigorating to see modern science trying to learn from and apply the traditional knowledge of amadou to a modern, practical application.

The etymology is pretty straight forward; where Fomes (from latin) means “tinder”, and Fomentarius means “used for tinder”. From what I’ve gathered, excatavatus means “cavity”. The tinder conk also has medicinal properties as a different study (Reference 4) that when the amadou was milled it had potent antioxidants and could even be used for cosmetic and agricultural applications. While lacking psychoactive compounds, this certainly is a mushroom packed with magic and it’s exciting to see scientists exploring all of its potential.

The tinder conk (F. excavatus F. fomentarius) is saprobic and grows on hardwoods – particularly birches. As mentioned, like last week’s Fomitopsis, this mushroom also comprises a “species complex” with several genetically distinct but physically identical mushrooms growing throughout the northern hemisphere. That’s the reason for the distinction between the Eurasian F. fomentarius and the North American F. excavatus, even though this particular species distinction isn’t widely embraced. The mushroom will grow alone or in a cluster with several running up and down whichever tree the fungus is digesting.

Another interesting feature is that you can age the mushroom by counting the rings that develop as the mushroom grows downward. The conk will stay on the tree and produce another layer of tubes each spring (from which the spores are released) which creates a horse hoof-like appearance. I’ve noticed a lot of tinder conks just produce one year of growth and then begin to decay. As the mushroom decays, both the external shell and pore surface discolor from white to brown/black which can make people confuse it with chaga – another desirable fungal growath. Below is a comparison of an old tinder conk and (young) chaga.

Old tinder hoof, hanging off the birch, with some Stemonitis growing from the bark to the right:

Chaga (it will slowly mound and grow in black, knotted chunks as it serves as a reserve of nutrients for the fungus):

I’ve been snowmobiling up in Maine, which is new to me, and while exhilarating it doesn’t allow for as much mushroom time as I would’ve hoped. Oh well, might have to dip back into the fall fungus archive for next week’s mushroom. Until then,


1) Kuo, M. (2010, February). Fomes fomentarius. Retrieved from the MushroomExpert.Com Web site:
2) – I couldn’t get the proper citation for the life of me.