Is it edible?

That’s the No. 1 question people ask about wild mushrooms. The thing is, there is no quick answer, and for good reasons.

Some edible mushrooms grow on wood. But so do a number of poisonous mushrooms. Some edible mushrooms have a ring or collar on the stem--but so do some deadly poisonous mushrooms. For ages people tried to establish convenient rules of thumb to sort out the toxic from the toothsome, but they all failed. One-size-fits-all rules simply don’t work with edible and poisonous mushrooms.

Here’s another example: Some poisonous mushrooms will tarnish silver when a silver spoon is used to stir mushrooms in a skillet. Some people used to drop a silver coin into the mushrooms while cooking. Unfortunately, not all poisonous mushrooms will tarnish silver. The only simple fact is that mushrooms must be properly identified before looking them up to find out if they’re edible.

And identification is not to be taken lightly. To the untrained eye, wild mushrooms can be tricky to identify because the diversity of colors and shapes is staggering.  Yet, somehow, they all seem to look alike--like all trees in the forest seem to look alike.  They’re all just mushrooms.

Scientists known as mycologists at the Field Museum in Chicago and elsewhere have been busy sorting them out, assigning scientific names to fungi and documenting their habitats and characteristics. Mycology is the study of fungi.

Did you know there are more than 1,200 different species of fungi identified so far from the Chicago region alone? For comparison, the entire state of Illinois has just 127 different species of native trees, and 186 different species of native fish. Unique fungi are everywhere in Illinois.

So how does anyone tell them apart?

Mycologists identify mushroom species based on a combination of field characteristics and microscopic features. A drop of blue liquid might appear when a certain species of mushroom is cut--that’s a diagnostic trait. Or the spores under a microscope might be shaped like a torpedo in some other species. Yet even mycologists cannot determine if a particular species is edible or poisonous based on its physical characteristics alone. For instance, a beautiful, snow-white mushroom might be deadly poisonous, while a deformed, pimple-covered “lump” might be a prized edible.

But a few mushrooms are quite easy to test. Some of the species of mushrooms known as boletes (pictured at left and at the top of the page), reveal a color change when something scratches the pores beneath the cap or cuts or bruises the tissue. That damaged surface turns darker, sometimes very quickly, and the color is often black or blue.

What does that color change tell us? People who collect mushrooms to eat know the majority of boletes that produce this staining reaction should never be eaten.

Of course, true to annoying form, not all boletes that stain are poisonous. Some boletes, such as the edible Old Man of the Woods (see: The Boletes “Edible Wild Mushrooms of Illinois and Surrounding States” 2009 University of Illinois Press) stain dark salmon, changing to black, when the cap or stem is bruised or cut. And there are still other frustrating exceptions: Many toxic boletes do not change color at all when bruised or cut.

But take heart: The hundreds of different species of boletes in North America happen to be one of the most challenging groups of mushrooms to identify to a species, despite this simple test which rules out many boletes as potentially toxic. Fortunately, since boletes represent just a fraction of all mushrooms out there, and since the most prized edible bolete in the world--Boletus edulis--really doesn’t occur in Illinois, foragers can simply skip all but the easiest of boletes and move on to better pickings.

Still, how do we know what’s edible among the thousands of species of fungi? Who tested all of these mushrooms?

A certain Captain Charles McIlvaine wondered the same thing back in the late 1800s. After the Civil War, this self-taught mycologist, armed with only a cast-iron stomach, decided to test the culinary value of wild mushrooms in America by eating every different mushroom he could find--everything but the well-known killers.

He could have died in the process--and he had some sickeningly close calls more than once--but eventually he ate his way across America and lived to publish “One Thousand American Fungi” in 1900.

Throughout the ages, humans have figured out through experience which mushrooms are toxic and which ones are safe to eat. Trial and error taught us that certain great edibles are quite distinctive and that there was really nothing else out there that represented a poisonous, mirror-image look-alike. The science of mycology arose from these basic human experiences. And while mycologists haven’t yet documented every species of fungus on Earth, the trial-and-error experiences dating back thousands of years still represent a strong body of knowledge. Long before there was a science called mycology, ordinary people knew that a morel mushroom was edible, and that a deadly Amanita would kill you. Cultures around the world today still have strong, active traditions of teaching new generations how to recognize certain mushrooms that are known to be safe and also the ones that are poisonous.

At last, this idea of walking outdoors to participate in nature is finally being discovered in Illinois and all across America.

It’s a perfectly natural choice, when you think about it.

And you really should think about it.

Identification tips for