Tom Volk's Fungus of the Month for May 2001

This month's fungus is Polyporus squamosus, also known as the dryad's saddle or pheasant's back mushroom

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Polyporus squamosus top and bottom Polyporus squamosus is a rather common fungus to find during April and May, when you're out hunting morels. Unfortunately this fungus seems to be more common than morels in some areas, mostly because they're quite a bit larger, up to 2 ft across sometimes! At least they're much easier to find than morels because they stick out as shelves from the lower portion of dead tree trunks, especially elms. This fungus generally fruits in the spring in most areas, but I've also seen it in some places in the fall season. They can grow to be quite large and stick out as shelves from the sides of trees near the base. These shelves have squamules (scales) on the upper surface that give it its species name. The genus name Polyporus means "many pores." Polyporus pores under the microscopeThe pores are lined with basidia that produce basidiospores. This serves to greatly increase the surface area and thus the number of spores that can be produced. Remember that the main function of a fruiting body is to produce spores that can be disseminated over a large area, to ensure that the fungus can spread to new sites where new food sources are available.

In the "olden days" Polyporus was a catch-all genus for any hard, wood-decay mushroom that had pores (instead of gills or teeth) on the underside. Now the genus Polyporus is restricted to polypore fungi

hyphal system of fungi A= generative hyphae with clamps, B= generative hyphae with simple septa, C= skeletal hyphae D= binding hyphaeTrimitic means that there are three kinds of hyphae in the fruiting bodies, as pictured to the right. I recently wrote a paper called "Polypore Primer: An introduction to the characters used to identify poroid wood decay fungi." It was published in 2000 in McIlvainea 14 (2): 74-82. As promised, that paper is now online! The purpose of this paper is to explain why the old genus Polyporus has been split up into more than 100 genera and the kinds of characters that are used to distinguish the genera.
I am often asked this question--- Why study polypores?
Polyporus squamosus on an elm treeAnyway, back to Polyporus squamosus. Where does it fit into our scheme of usefulness above? It is an important decomposer, very commonly found (in our area, anyway) on dead elm trees. It causes a white rot, so it is able to digest lignin. It's not clear how much of the cellulose is also digested by this fungus.

This mushroom is also reported to be edible. I say "reported" because I have never been able to cook it in any way that I would consider delicious. The main problem is its very rubbery texture. It has been recommended to use only very young specimens and to slice it very thin before cooking very slowly over low heat. I've tried many times (including the recipe in Bessette, Bessette and Fischer's recipe book), but I *still* can't get this mushroom to be edible. I would not consider serving it to anyone I was trying to convince that mushrooms are a good thing to eat. If I were lost in the woods and starving I might consider it great. At least it's not known to be poisonous...

I understand this fungus can also be used for making art paper. Many polypores, especially the trimitic and dimitic ones (with those thick-walled hyphae), can be used to make very thick stiff beautiful paper, much in the same way that cellulose fibers of wood are used to make regular paper. I've never tried it myself, but I've seen some beautiful paper made by people at mushroom forays.

my sister Rosanne sits on a Dryad's saddleSo, what about the common names for this mushroom? The "pheasant's back mushroom" is quite obvious from the above pictures. Many a hunter has been startled in the woods or has stalked one of these mushrooms thinking it was a pheasant seen from the back.

a dryad from www.devoted-dryad.comDryad's Saddle is a little more complicated. You're thinking "what the heck is a dryad?" Well in Greek mythology a dryad is a tree-dwelling nymph, also known as a tree sprite. Someone with an overactive imagination decided that Polyporus squamosus looked like a saddle that one of these tree-dwelling nymphs would sit on. To the right you can see my sister, Rosanne, pretending she's a dryad and sitting on the saddle. I took this picture several years ago before she lost a lot of weight. So if you're ever with me and my camera in the woods, be careful when I ask you to do something odd so I can take a picture. You never know when that picture will show up...

I hope you enjoyed learning something about Polyporus squamosus today. When a fungus has a common name there's either something very good or something very bad or something very distinctive about it. The two common names for this fungus both lead to interesting stories about it. Be on the lookout for it in the woods this month. And if you find a delicious way to prepare it, please let me know....

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This page and other pages are © Copyright 2001 by Thomas J. Volk, University of Wisconsin-La Crosse.

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