On a cold September night in Chapel Hill this past Fall, I shared one Chlorophyllum molybdites button and two Macrolepiota procera with three friends. It's a wonder we're still friends.
The green-spored parasol, C. molybdites (a.k.a., the "gut wrencher") is the #1 poisoner on the continent, causing more GI trouble than Abu Graihb. Reactions vary, however, and that night, only two of us got significantly ill. For better or worse, I was not one of them.
How do we explain our different reactions to one very poisonous mushroom? First of all, by the fact that not all four people ate it: one guest did not. Why then did that guest and at least one other have similar symptoms? Probably from something else we ate; namely, other mushrooms.
By my reckoning, we ate five different mushrooms that night, and it looks like at least two were problematic. Of course this made it harder to figure out what was happening, which is why you're supposed to eat only one type of wild mushroom at a given meal.
In part one, I discussed four out of the five suspects. I talked about how many mushrooms, including Boletus bicolor and the green-spored parasol, are edible to some but not all people. In this final installment, I'll cover nine ways to distinguish M. procera from its duplicitous double, C. molybdites.
The green-spored parasol is known as a "partial." It doesn't poison everybody. When I ate it, however, I wasn't hoping for favoritism; I was hoping it was something else.
C. molybdites is the spitting image (pun intended) of the parasol mushroom, Macrolepiota procera (note that C. molybdites is a parasol but not the parasol). The parasol is one of my favorite mushrooms, and I'm not alone: it's one of the most sought-after edibles in North America. That night I shared it with others, I thought I had three of them. Unfortunately, in this case two out of three is bad. How could I have told the perilous parasol apart from its comestible kin?
The classic difference between C. molybdites and M. procera is spore color: greenish vs. white, respectively. Of course, you can't just look for green around the gills (unless you want to end up that way). The prime directive for parasol safety is to take a spore print. Unfortunately, it can take days after a C. molybdites fully opens for it to form spores; some are just plain sterile. That means that a green-spored parasol spore print taken on white paper can appear white even though there's really nothing there. And that's exactly what happened in 2005– with infelicitous results– to an English professor who'd been picking mushrooms for years (and I thought my philosophy degree was useless!).1
Of course, to avoid culinary catastrophe, one can scrape the paper to see if any spores come off or just use brown paper or tin foil instead. But that won't help if your mushroom has not even opened yet. The mushroom I had was still in the button stage. I did put a piece aside just in case, and later microscopic analysis proved that there were no spores to be found.
At this point most books simply say, "if you can't get a spore print, don't eat it." Quit while it's a head. On that cool afternoon, however, not having a spore print wasn't the main problem. My main problem was that I wasn't watching out for C. molybdites in the first place.
When my friend first brought me the mushroom, I was holding two parasols also picked that day on the premises. I thought, this looks exactly like a parasol. It's definitely not an Amanita; it's not an Agaricus, either. What else could it be? At that moment, despite fifteen years of mushroom hunting and ten years of teaching, the very existence of the green-spored parasol, America's Most Unwanted (at least eight poisonings each year, and not just beginners2) completely slipped my mind.
At the time I carried half a dozen mushroom field guides in the car with me everywhere I went. Surely any one of them would have alerted me to the parasol's treacherous twin.3 And had I known of this possibility, I surely would've figured out what it was. But how many times is one going to look up a mushroom they've picked dozens of times before they decide they know it already? It's a scary thought: that as mycologists get older, they get bolder. But at 38, I'm too young to be senile!
There are two things that could have told me, look this one up. One was the fact that I hadn't picked the mushroom myself. When I asked where friend found it, he said "in the horse pasture near the gate." That's the second classic difference between C. molybdites and M. procera, namely, habitat: grass (including under trees) vs. mulch or open woods. But it just didn't sink in. Neither did the fact that when I cut it, the stem turned a weak red. That's funny, I thought, I can't recall if M. procera is supposed to bruise red. I thought it didn't, and I still think it never does, although later research showed that the books disagree on this. But I didn't look in any book to begin with because again, I completely forgot that C. molybdites existed. At least I'm admitting it now!4
As I sliced up our erstwhile treat, I told my friend, another well-known wild-foods "expert" (we were scheduled to teach a workshop organized by our host the following month) that I wasn't sure about this. He said, "I'm sure you're right." It's true that I supply wild mushrooms to more than two dozen restaurants, and I would never have sold them a questionable mushroom or served one to a class, but this was just us. Our host even made a toast before eating the dubious dish, saying something like, "if we all die from eating this mushroom, here's to the memories." I remember noticing her eating a lot more of it than I was, and deciding it better (since there wasn't much there to begin with and it's easy to scare someone into getting sick) not to say anything. Thank goodness I'm not plagued by Jewish guilt!
The third classic difference between the green-spored parasol and "the" parasol is season: Summer to Fall vs. Fall. It was late September and it was already quite cold, yet this mushroom, like a number of true parasols still coming up around the house, was still a button. That's part of what confused me. The green-spored parasol usually pops up in warm weather while the parasol prefers cooler conditions. But the fact, as I later found out, is that their fruiting times can overlap– significantly. Leon (our faithful editor) tells me that in recent years, C. molybdites has been known to come up in "downright chilly" weather (and that's coming from a Chicagoan).
When I went back to the meadow where the mushroom had been picked, I found a cluster of ten or so parasols, already long gone. They were too old to identify based on their looks, but the fact that there were several points strongly to C. molybdites. That's difference #4, growth pattern: in groups vs. singly. It's unusual for C. molybdites to fruit alone, yet this is quite typical of M. procera.
The next morning, I called the mycology lab at Duke to see about settling the matter scientifically. Greg Bonito, a grad student I'd met at a fungus fair two weeks before, offered to help. So I packed my sample piece along with a genuine M. procera we had in the fridge and set off for Durham. On my way out, I picked up an old parasol from the horse pasture. Then, driving through town, I spotted a patch of fresh C. molybdites. With one of these in hand (I'm sure the homeowner won't miss it), I had a full set of samples for comparison.
In the lab room, Bonito put one sample after another under the microscope, subjecting them to chemical testing as well. After two hours, the results were inconclusive, but given their respective staining reactions, the look of the cheilocystidia (i.e., the edge of the gills), and the fact that it was freezing in there, Greg was satisfied that we had indeed collected C. molybdites.
Later I wondered what I could have gleaned about my mystery mushroom without a microscope or spore print. I found that besides habitat, season, and growth pattern, there are actually several differences in appearance between the parasol mushroom and its wishyou- were-dead-ringer, C. molybdites. Hopefully these can help you avoid untoward unpleasantries. Keep in mind, however, that like all mushrooms, parasols can be quite variable; M. procera, in fact, may soon be split into several species.5
The main morphological difference between M. procera and C. molybdites, one which is surprisingly underrated in the books, is that the parasol mushroom has a snakeskin pattern on the stem. It doesn't always cover the entire stem or even most of it, but this is something C. molybdites never has any of. Difference #5, then, is stem decoration: plain white or brownish vs. snake skin.
There are two other, albeit less obvious, differences in the stem as well. The first is stem thickness: 1/3 vs. 1/8 the button cap width. Although their overall size is the same, the stem of the green-spored parasol is at least 50% thicker than that of the edible parasol. You can see this if you look through the pictures in several books.
Next is the shape of the base: weakly vs. abruptly bulbous. C. molybdites' base is clavate: it widens less and more gradually than that of M. procera, which widens abruptly into a ball. Of course you can't use this feature if you break off the base and leave it in the field, as my friend unfortunately did. Even then, a third noticeable difference already mentioned between C. molybdites and M. procera is flesh staining: weakly– though not always– turning red vs. not at all.
The final difference, I regret to announce, is in the taste: C. molybdites has a decent meaty flavor when cooked, but lacks the distinctive "roast beef and walnuts" taste of M. procera. I remember thinking when the sliced mushroom started to stain: well, I'll be able to tell from the taste. But then, the flavor of M. procera– like Lepiota americana, another mulch-sucking parasol– is quite variable, depending on what it's eating. Plus, by that point, inertia was working against me (and you know the rest).
So these are my lessons learned. I certainly haven't stopped eating wild mushrooms, and that workshop went on as planned– without incident. Even my host was ready to eat parasols again a week later. For, like I said in part one, the benefits of wild food are well worth the risks. Stick to store-bought and restaurant food and you have Salmonella, Staph, and Hepatitis and E. coli to contend with– not to mention trans fats, GMOs, irradiation, and countless other miracles of modern manufacturing, all leading to cancer and other degenerative diseases. Even so-called "organic" food can be unhealthy.6
Mistakes are a part of life; we might as well laugh about and learn from them. I remember the time I almost ate C. molybdites ten years ago: it was literally in the pan when I noticed the green gills. Things almost went to pot that time. But I was just a foolish amateur then. Look at me now!
1 Dave Miller, "How to Get (Really) Sick from Eating Wild Mushrooms," The Mushroom Log, Newsletter of the Ohio Mycological Society, Nov/Dec 2005, http://www.ohiomushroom.org/oldoms/novdec/NovDec05.htm.
2 Beug, Shaw, and Cochran, "Thirty plus Years of Mushroom Poisoning: Summary of the Approximately 2,000 Reports in the NAMA Case Registry," text available (charts on request) at http://www.blogcharm.com/mycos/, and http://www.mushroomexpert.com/chlorophyllum_molybdites.html.
3 While writing this article I attended a party where the host brought me all three mushroom field guides in his possession. I don't go to parties to read field guides, but in order to look appreciative I decided to look up M. procera. It was listed as edible and choice in all three books; however, C. molybdites was not even mentioned in any of them. I suspect that these are all books from Europe, where C. molybdites is virtually unknown.
4 Note that many books list the shaggy parasol, Macrolepiota rachodes– which does stain strongly red, at least when young and fresh– as the look-alike to C. molybdites. In fact, as of 2002, M. rachodes is now Chlorophyllum rachodes! In the east, however, M. procera is far more common and in my opinion, more similar to C. molybdites than Macrolep– I mean Chlorophyllum– rachodes.
5 this may solve M. procera's apparent partiality: according to Leon, the mushrooms responsible for the two reported "proceroid" poisonings were both smaller and thinner than procera usually is and are probably a different species (MTJ, Summer 2006, p 42). It sure would be nice if the poisonous ones could be distinguished this way.
6 see Sandor Katz, The Revolution will not be Microwaved (Chelsea Green, 2006) and/or Michael Pollan, The Omnivores Dilemma (Penguin, 2006).