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The Amateur Mycologist #9 - Boletus edulis - The Porcini

The Amateur Mycologist #9 - Boletus edulis - The Porcini

These posts are not for foraging. They are intended for entertainment and educational purposes only. These posts are not a field guide nor comprehensive in any way - their accuracy is not assured in any way. Do not eat wild mushrooms unless you are a professional or have a wealth of personal experience with a specific species. Do not make any foraging decisions based on these posts.

These Posts Contains No Information Regarding Edibility Or Toxicity


Today we discuss what many consider the king of all mushrooms: Boletus edulis, most commonly known as the Porcini.


Take a look at that mushroom. Few specimens are as exciting and visually satisfying to find as a mature, undeteriorated Porcini, or one of its close cousins. B.edulis and B.edulis-like mushrooms grow all over the world. You can find these mushrooms from China, through Russia, across Europe and North Africa, and all the way across the ocean in North America and parts of Mexico. As long as you're in the northern hemisphere, you can find some variation of this mushroom in a forest near you from June through November.

Why do I say "nearly identical" and "B.edulis-like?" As with so much of mycology since the advent of DNA analysis, the old paradigms of B.edulis identification have changed. It used to be mycologists were satisfied referring to B.edulis as roughly one widespread species of the Boletus genus. However in the last decade, DNA analysis has again shown that what was once considered a single overarching species is actually a humongous diversity of genetically unique mushrooms.

As a result, if we're being technical, true B.Edulis species probably only grows in Europe, whereas the rest of the world has B.edulis lookalikes. Luckily, this distinction is mostly academic. For forest traipsing bolete hunters around the world it changes almost nothing. You might end up with a Boletus rex-veris, pictured below, instead of a B.Edulis, but you'll still be satisfied.


If you're hunting in North America and interested in discerning the exact species of a B.edulis type mushroom, you can use Michael Kuo's key to B.Edulis, or buy an identification book exclusively for boletes. However, for those of you less inclined to extreme detail, there are certain macro characteristics which can clarify if you're within the broad range of B.edulis-like species and variants.


First, as with every species of Boletus, the spore surface is porous.

If you cut the cap in half, you can see in the cross-section that the pores are in fact thin tubules meshed together to make a cohesive whole.

This pore surface starts out white, then becomes yellow with age, eventually turning olive brown. If you bruise the pores with your finger, they should not change color.

The cap of the mushroom is usually plump, convex when young and then flattening out in the older specimens, with the edges sometimes turning up to reveal the pore surface a bit. The cap can grow to nearly a foot in diameter, although most specimens will be less wide. The cap color of the true B.edulis is reddish brown and gets darker as the mushroom gets older. But several close relatives can be lighter in color.

The stem of B.edulis has as much character as the cap. Often wider at the bottom and tapering toward the top, it should have a consistent white flesh throughout when young. The height varies widely as well, from 3 inches up to 10 inches. Young mushrooms should be undifferentiated white flesh and firm, rather than spongy. When you cut the flesh it might discolor to brown or red.

One thing to look for in judging the quality of the mushroom is to bifurcate the stem and look for the bore holes of insects inside. Ideally the flesh should be white through and through - but often it will be cut through with insect tunnels.



Macroscopic Features:

  • Cap = Convex at first, then flattens as it gets older, ranging in size from 2.8 to 11.8in (7-30cm). Gets darker as it matures, generally reddish brown and lighter around the edges. A bit sticky to the touch, especially if wet.

  • Spore surface = fairly deep, whitish pores when younger, yellowing with age until finally ending almost light olive. The pores don't change color when damaged or pressed with a finger,

  • Flesh = White. Sometimes a bit of brown near the base of the stem. Firm when young, becoming spongy when older. Mixed reports about whether damage changes color of the flesh - wikipedia says possibly light brown or light red change. Boletales says no change. No distinct taste

  • Stem ("stipe") = 3.1 - 9.8in (8-25 cm) high and up to 2.8in (7cm) thick. Often club like, cylindrical but sometimes with a taper, sometimes bulbous or swollen looking. Reticulation on the exterior of the stem is well defined, fading near the bottom of the stem. White pattern on darker background. Bifurcation should show an undifferentiated white flesh through the stem.

  • Spore Print = Olive Brown

  • Ecology ("How it grows.") = Mycorrhizal (In a mutually beneficial symbiotic relationship) with certain trees - primarily conifers (sprice, fir and pines) as well as some deciduous tree - (beech and birch). Therefore will often be found by these trees.

  • Distribution = The genetically true B. Edulis may only really be in Europe. However, B.Edulis like mushrooms span the globe.


Disclaimer 2

The only 100% way to avoid being hurt by a wild mushroom is not to eat a wild mushroom. These posts are not field guides - they are intended for the mycology enthusiast, not the forager. If you want to forage mushrooms there are professional resources available to that end online as well as local mycological societies all over the world which you should connect to for guidance.


For The Online Mycokey program look Here

For a Glossary Of Relevant Mycological Terms, Micheal Kuo's Website Provides


Information Sources:

http://www.mushroomexpert.com/boletus_edulis.html https://en.wikipedia.org/wiki/Boletus_edulis http://www.mykoweb.com/CAF/species/Boletus_edulis.html https://en.wikipedia.org/wiki/Rubroboletus_satanas https://en.wikipedia.org/wiki/Tylopilus_felleus http://boletales.com/genera/boletus/b-edulis/

Photo Sources:

1 2, via Wikimedia Commons) 3, via Wikimedia Commons) 4 via Wikimedia Commons) 5 GFDL 6, vie Wikicommons) 7, via Wikimedia Commons)

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