Caesar's Mushroom

First off: wow! Busy summer. It was busy in a very positive way, but that did lead to two things 1) fewer outdoor excursions and 2) less time to post about them. But I have not abandoned this blog (for entirely selfish reasons; it's a lot of fun and strokes the old ego a bit). Luckily for me, it rained a lot in August/September and thus the mushrooming improved quite a bit. As such, I've accumulated a backlog of images and information to share here.

Astute observers with epic memory will note the absence of a "species feature" title and tag to this post, and there's a good reason for that. What reason? The mushrooms I'm talking about might not even be Caesar's mushrooms (Amanita caesarea) at all. The problem is, A. caesarea is notoriously difficult to distinguish from varieties of A. muscaria in this part of the world - specifically var. formosa and var flavivolvata. It's one of nature's cruelest traps - those varieties are both more similar to Caesar's mushroom and more dangerous than their European counterparts. On either side of the pond, A. caesarea is a choice edible. European varieties of A. muscaria, better known as fly agaric, reportedly cause hallucinations, and are sought after for this purpose. However, the U.S. version will just get you violently ill. It's like a ripped off BBC show that way. Michael Kuo (splitter!) has the North American version of Caear's mushroom as A. Jacksonii, a distinction that further confuses things. Kuo is probably technically correct, but for simplicity's sake I will be discussing the species as Amanita caesarea.

This is the nicest specimen of the alleged A. caesarea I have found. It was a lonely giant of its kind in Rock Creek Park earlier this month.

Before proceeding, I must include another mushroom-eating disclaimer. Don't use my blog as your primary resource. Don't eat mushrooms based on my advice. If you use my blog as inspiration to go learn enough to eat wild mushrooms safely, more power to you.

Now for some good news. I believe the similarities between A. caesarea and A. muscaria var. formosa (I can't speak directly to var. flavivolvata, because I've found no specimens of this) are overblown. Mushroom writers are rightly concerned about an amateur making a mistake based upon their descriptions and getting sick or worse. Some of the differences are in superficial or non-persistent characteristics, which are not usually the best aid to getting an accurate mushroom ID. They are both members of the genus that includes species with such common names as "death cap," "destroying angel" and "fool's mushroom." Amanitas account for 95% of mushroom-related fatalities (thanks Wikipedia). All of this leads to understandable caution. (For more on this general topic, see this entry from a fellow local mushroom blogger.) Fortunately for mycophagists, the deadly ones are much, much easier to distinguish from our hero. This leaves a knowledgeable field mycologist with only the risk of illness - and not much risk of that with enough experience.

Amanita muscaria var. formosa, as found in Watkins Regional Park some time ago. Pictures are not the most reliable way to distinguish mushroom species, but taking a close look at these first two photos is a good start.

How these two species are alike:

Both of these mushrooms exhibit classic Amanita features: the spore print is white, they have both universal and partial veils which persist as volvae (please don't confuse this with vulvae) and rings on mature specimens, their gills are free from the stem.  They are also similar in size, habitat, and season. Both are mycorrhizal with hardwoods and with pines. Both have yellow-to-orange coloring on their caps and white flesh. A key to successful mycology, however, is to learn which things are different and isolate them. Of course, one doesn't want to do so to the exclusion of these basic features, but with experience noting the Amanita characteristics will become second nature, and allow one to focus on some other details.

How these two species are different (the key features):

I think the simplest difference to detect is that A. caesarea has yellow gills while A. muscaria has white gills. This isn't a perfect test, because yellow gills can be so pale as to appear white, and white gills can appear yellow beneath a yellow cap in poor lighting. Another helpful difference can be found around their respective volvae. A. caesarea has a much larger, more persistent volva. A. muscaria tends to have shaggy "skin" near the base of the stem where it meets the volva. Caesar's mushroom has a yellowish stem while fly agaric has a white stem (again, the yellow can fade). Finally, A. muscaria not only has, but is famous for, white warts on top of its cap.  A. caesarea lacks these warts. Any one of the four preceding features is not a sure bet - but all four? Solid. I suppose it is remotely possible to find a specimen of A. muscaria whose warts have fallen off, that has an abnormally large volva and lacks a shaggy stem base, and which appears yellowish in the gills and stem. But doesn't that seem like a long shot to you?

Here's a closeup of the volva of Caesar's mushroom.

This shot was meant to demonstrate the yellow stem and gills - but it also inadvertently
demonstrates how it can be hard to tell if the gills are yellow in the field.

 

Luckily I have this old photo - here you can see A. muscaria var. formosa's  white gills, white stem, and smaller volva. You might be able to pick out the shaggy bits at the stembase as well.

Additional apparent differences:

These are why I think the chance of mistaking one of these mushrooms for the other is slim for careful and experienced mycologists. I will admit the possibility that I'm just not experienced enough. Maybe I'm misidentifying everything, and the range of variability within each species is broader than I think. This is why I've yet to eat any Caesar's mushrooms.

The bulk of these differences are in the caps. Look at the photos of the two species.  Don't they seem quite different? A. caesarea is distinctly orange*, shiny, very striated at the margin, lacking in warts, and possessed of a distinct umbo (that's the bump in the middle). by contrast, A. muscaria var. formosa is pale yellow with slight striations at most, many warts, and no umbo. Using these features for IDing a mushroom is a lot like performing a physical task with bad form - positive results are possible, but you're not putting yourself in the best position for achievement. All of those features are variable within each species and can be changed by the environment, given time. And yet, every time I have collected a specimen of either of these species, it has gone this way: I have noted at first glance that it superficially resembles one species or the other. I have taken notes, brought the specimen home, and obtained a white spore print. Upon examining the four key features above I have corroborated my field guess. This has held true for four or five ocurrences of each species. So what I'm saying is that in theory this group of features is not to be used as a definitive identifier, but experimentally they hold up as a reasonable predictor and starting point.

*since these mushrooms are named for a certain Caesar who purportedly had a taste for them, have I discovered the origins of the name "Orange Julius"?



In addition to the links above (mushroomexpert.com, wikipedia, roger's mushrooms, and the free dictionary) I used the following texts as sources: The National Audubon Society's Field Guide to Mushrooms: North America, Simon and Schuster's Guide to Mushrooms, 100 Edible Mushrooms (Michael Kuo), and Field Guid to Wild Mushrooms of Pennsylvania and the Mid-Atlantic (Bill Russell).