Saturday, 31 May 2014

Gyromitra esculenta and Gyromitra gigas: Two False Morels

Gyromitra esculenta contains toxin gyromitrin
Gyromitra esculenta contains large amounts of the toxin, gyromitrin.
When we first moved to east-central Ontario, old timers on our road told us they'd seen people coming out of our woods every spring with garbage bags filled with morels. Green garbage bags! So every spring we've battled black flies and mosquitoes, and poison ivy so fresh you just have to look at it to get a half-body rash, in search of this mythical motherlode, and every year we've fallen short. A few morels, yes. Garbage-bagsful, absolutely not.

What was going on? Where were these famous mushrooms? I finally figured it out when, one May day, I bumped into a stranger in the woods. A stranger with a big bag full of...not delectably edible morels, but false morels—Gyromitra esculenta, to be precise. He'd been eating them for years, he told me. 

"Maybe not for many more," I suggested, a less confrontational reply, I decided, than starting a discourse about trespassing.

Gyromitra esculenta is not hollow like morels
Unlike real morels, false morels, like Gyromitra esculenta, are not hollow.
Though we could, indeed, easily fill garbage bags with the crop of G. esculenta that pops up in our local woods every spring, we won't be eating any of them, because they, and several other Gyromitra species, contain varying amounts of gyromitrin, a toxin and probable human carcinogen that metabolizes in the body into—believe it or not—rocket fuel (monomethylhydrazine). 

Though people claim that by using specific cooking methods they can render various Gyromitra species edible ("esculenta" actually means "edible"), there may be long-term cumulative effects of the toxin, and 2 to 4 percent of all fungal fatalities are associated with them. Before anyone convinces you to try eating one, please read Tom Volk's excellent page on their toxicity.  

Though there's a fall species in my area, G. infula—that's usually saddle-shaped and grows on rotting logs—the only spring one I've found around here is G. esculenta. Last weekend, though, on a Mycological Society of Toronto foray northeast of the city, we found a different one.

Gyromitra korfii is less "brainy" than G. esculenta.
Gyromitra gigas looks less "brainy" than G. esculenta.
I have no photographs of it in place because, before I plucked one for display, it fooled me into thinking it was G. esculenta. Its fertile surface was a warm brown, and it was somewhat contorted. I didn't look at it closely until I got back to the parking lot and saw that it was less "brainy" looking than usual, had an abnormally stout stipe, and, when I cut it in half, had cottony white material in its convoluted interior. It wasn't  an abnormal G. esculenta, it was G. gigas, (often split into G. korfii in the east, and G. montana in the west).

Gyromitra korfii cross-section
Gyromitra gigas has a convoluted interior.
Interior of gyromitra korfii is cottony
Cottony interior of Gyromitra gigas
Gyromitra esculenta and G. gigas differ even more different under the microscope. The spores of G. esculenta are kind of nice in their smooth, fusiform to elliptic clarity, usually containing two oil droplets at either end, while those of G. gigas are slightly roughened and fusiform, with several small oil droplets orbiting a larger central one. Most notably, though, the spores of G. gigas have two knob-like apiculi at either end.

False morel spores
Gyromitra esculenta spores have two oil droplets.

Gyromitra gigas asci, spores, and colored paraphyses.
Gyromitra gigas asci, spores, and colored paraphyses.

Gyromitra gigas spores have knoblike apiculi on either end.
Gyromitra gigas spores have knoblike apiculi on either end.
Gyromitra gigas apparently contains much less gyromitrin than G. esculenta, and is thus generally considered to be a safe edible, but since this G. gigas appears to be a species complex that may vary considerably from place to place I think I'll wait until more study is done before eating it.  


Gyromitra gigas on Mycoquebec
Gyromitra esculenta on Tom Volk's Mushroom of the Month

Tom Volk's excellent page about Gyromitra toxicity.


  1. We have eaten 'beefsteaks' for years and one ever got sick from them...and we just fried them up in butter like the morels.

    1. Did you read this link to Tom Volk's page I know these fungi are still regularly eaten, but it seems only fair, as Tom says, that you don't feed them to guests without having them read his page about their toxicity.

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  2. this all old news, a new study revealed that frying after boiling Gyromitra esculenta removes all the toxin gyromitrin from the mushroom.

  3. Just found Gyromitra esculenta today in my woods (spruce-fir-aspen-birch). Then happened upon your site (again) while reading up on it and saw the photo of G. gigas and wondered if I had found that last year in the same woods. It's on my Flickr site under the title "Geopora or Hydnocystis?" which is what I thought and hoped it might be. Now I'm not so sure. I found it on June 22 growing on well decomposed log.

    1. Your image from last years show a Gyromitra infected by Sphaeronaemella helvellae. This ascomycete distorts its Gyromitra sp. hosts, making them difficult to identify:

    2. Thanks! If I see any fungi like this again I'll take a closer look to see if the velvet surface is really another fungus.