Identifying mushrooms: There is more to it than you might realize

The best way to learn how to identify mushrooms and fungi is to join a local mycology association and get hands-on experience with experts.

Following the extended period of rainfall, mushrooms have been popping up everywhere, and along with them, emails and photos from people wanting me to identify mushrooms they have found in their lawns. With regret, I reply to them that I do not identify mushrooms or answer questions about their edibility. What we commonly refer to as a mushroom is only part of the organism, known as the fruiting body, that pops up to distribute spores. Much more of it remains hidden, growing underground, perhaps forming a mutually beneficial association with the roots of certain trees, or growing on decaying wood, or converting organic materials into humus. While there are a few mushrooms that are sufficiently distinct in appearance that they are relatively easy to identify, many more are not. The consequences of misidentifying mushrooms can result in more than an upset stomach for someone who eats them – it can be fatal – and that is one reason why I don’t identify mushrooms.

Among the diagnostic features used to identify mushrooms are the size, color and shape of the cap and stem; whether the underside of the cap has pores, gills or teeth; the absence or presence of a veil; the color of the mushroom and its flesh. Whether or not the flesh changes color after it is bruised may also provide a clue to its identity. It is important to note where the fungus grows; some fungi have mycorrhizal associations with particular tree species, others colonize rotting logs, or colonize living trees. Some fungi have a distinctive odor. Some mushrooms produce a color change when specific chemicals are applied to the surface, flesh or spores. This can include ammonia, potassium hydroxide or iron salts. Some spores produce a color change when iodine is applied.

One of the most important features used to identify mushrooms is the spores. Some fungi have distinctly colored spores, which can be seen by making a spore print. A spore print can be made as follows: Choose a mushroom that appears mature – one that is in the button stage won’t leave a print. Place the mushroom cap facing downwards on a piece of glass or Plexiglas. Cover it with a cup or glass placed upside down over the cap to prevent air currents from distributing the spores. Leave it overnight. The next day, the spore print can be checked against light or dark paper as needed to see the spore color. Spores are viewed under a microscope to check size, shape and color, and are very small, measured in microns (25,000 to an inch).

By now, you have probably realized why it is nearly impossible to identify a mushroom from a photo sent via email. If you are really interested in learning more about correctly identifying edible fungi, there are several organizations that welcome people new to mushroom identification to attend their forays and provide opportunities for them to learn from members who are well versed in mushroom identification. One such organization is the Michigan Mushroom Hunters Club.

Photographing fungi and learning to identify them can be an enjoyable hobby. If you are looking for a couple of good websites with color photos of fungi (but don’t use them for trying to identify a mushroom to eat!), visit the Mushroom Expert and the University of Wisconsin-La Crosse's Fungi websites.

Be aware that there are many different types of mycotoxins that are present in mushrooms. A good website to find out more is at the North American Mycological Association website, which includes detailed descriptions of mushroom poisoning syndromes and their symptoms.

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