Mushroom ID Part II

Determining unknowns

Identifying an unknown mushroom is a methodical process. The basic process is:

  1. Observe and document as many key features as possible.
  2. Use a dichotomous key, commonly called "keying out", to narrow down your possibilities.
  3. Read the descriptions of your closest matches, review the photos, and decide if your unknown is documented in your guide.

I will describe the identification process that I personally use. My method typically involves documenting key features in the field, but digging into the books after the foray is over. This method requires that you take good notes, and good photos! You will want the following materials:

  • A digital camera, preferrably with a macro function for short focal length. A small tripod is especially useful, as you often will be taking photos in low light.
  • A small notepad and pen that is easily carried
  • Some item that can provide scale and isn't obnoxious should you want to share your photos. I use a 6" metal ruler.
  • Recipe cards for sporeprints. It is best to draw a thick black line across the middle, so that white spores are also visible.
  • Your field guides. In addition, an internet connection can really help. Many great identification resources exist online.


Documenting key features

As you could guess, you won't be able to arrive at a proper ID without checking out all the key features of the mushroom in question. What you want to generate is a list of features that you can compare to the feature list of potential candidates in your field guide. These features will be essential in the "keying out" process, which is based on feature combinations.

The Identification Pt. 1 section of this website is dedicated to major key features. Each category in the Identification Pt. 1 section was specifically chosen based on the major features that are noted in field guides. Become familiar with these, and note them as you see them.

Almost every feature should be visible in the field. The only one requiring additional effort is the spore color. Sometimes, you will be fortunate and find a spore deposit on materials beneath the mushroom cap. But when you don't, you'll need to collect a sporeprint.

I prefer to keep a small notepad with me, and for each specimen, document all the key features I can on a single page. I'll label the page with a number, which will correspond with photos and a sporeprint.


Field photography

For me, photography is critical to my identification process. In the field, you are often surrounded with distraction and constriction: mosquitos, poor weather (or the promise of), limited time, and the allure of ever more interesting mushrooms to find. It is a great relief to know that your field work is separate from your academic work; you can save the book delving for the campsite / office.

When you are taking photos to support the identification process, your approach will be different from purely aesthetic photography. The basics still apply, of course, such as proper focus and lighting. But the ultimate goal is to capture as many key features as possible in the photograph. You are photographing the specimen in lieu of gathering it. This gives you the advantage of always having access to the mushroom in its fully hydrated, undamaged state. Would you expect a picked specimen to remain pristine in your basket after a day's worth of hiking the woods? This is not to say that you shouldn't hold on to your specimens. If you think your find is interesting and uncommon, you could dry it out and submit it to the Arizona Mycota Project.

Here is a list of tips for getting the most out of your field ID photos:

- A picture is worth a thousand words, but you determine the grammar.

Remember that your photos are for your reference, and if taken well, will posess all the info present in your field notes. If you use my approach, your photos will be a major source of information when you get back and try to determine the ID of your unknown mushrooms. In comparison, if you keep a physical specimen, it will probably experience some changes such as dessication, discoloration, or damage. Keep that in mind, and the rest will come naturally.

- Take photos that show the most key features possible.

Photos from directly above or from too far away are not useful. It is important that in a single photo you convey as many features of the mushroom in question as possible. The exception would be a photo that shows habitat and fruiting pattern; but even then, you often can take the photo at such an angle that a good array of characters are discernable. Equally, try to include the whole mushroom in at least one photo.

- Include more than one specimen of the species in question.

The most useful photos will include more than one specimen of the same species. Immature mixed with mature is a great combination. The best use of a second specimen is to present it in a way that will include additional key features in a single photo. For example, taking a photo of a mushroom from above and to the side, with a second specimen lying with its underside showing.

- Try to show habitat in your photos

Habitat is an important character in the identification process. So, not only should you have a photo with the whole mushroom, it should show enough of the habitat to help with your decision making.

Be sure to check out these great mushroom photography tips:

Michael Kuo's photography tips
Korak's Photography tips's top ten photography mistakes
Using your macro setting properly

Keying out unknowns

Most field guides have a step by step process of narrowing down the identity of your mushroom based on its key features. This branching selection process is called a dichotomous key, as you make yes/no choices to arrive at a possible match. Using this identification method is referred to as "keying out".

Here is a good example of a dichotomous key, as taken from

Key to Gilled Mushrooms

1. Mushroom small (cap 1-5 cm); cap and stem brown; growing on the ground; without a partial veil or universal veil ; odor strong, reminiscent of cucumbers or fish; spore print white, pinkish, dirty yellowish, pale brownish, or a mixture of these colors; cap, stem, and gills covered with prominent cystidia . Macrocystidia cucumis

1. Not completely as above. 2

2. Spore print pink, flesh-colored, or salmon. Gilled, Pink-Spored

2. Spore print otherwise colored. 3

3. Gills very thick, waxy, distantly spaced, yellow, running down the stem; mushroom appearing from above much like a bolete ; spore print yellowish to brownish. Phylloporus

3. Not completely as above. 4

4. Spore print orange. 5

4. Spore print not orange. 6

5. Growing on the ground; flesh somewhat crumbly. Gilled, Pale-Spored

5. Growing on wood; flesh not crumbly. Gilled, Dark-Spored

6. Spore print white, creamy, buff, yellow, lilac, or pale greenish. Gilled, Pale-Spored

6. Spore print darker than above (brown, cinnamon, rusty, purplish brown, dark gray, black, etc.). Gilled, Dark-Spored

Kuo, M. (2007, March). The gilled mushrooms ("Agaricales").
Retrieved from the MushroomExpert.Com
Web site:

In the above example, there are additional keys in the Gilled, Dark / Pale Spored categories that continue the process.

It will be useful for you to keep track of your route through the key. If you come across a decision that could go either way, write that down and come back to it if you arrive at an ID that you disagree with. Try different routes on the close call decisions, and you may find an ID that you can agree with.

Making your final determination

Once you arrive at a possible ID for your unknown, you will need to confirm wether this entry correctly describes your unknown. You need to scrutinize every key feature listed in the description, and compare it to your notes. It is not uncommon to find minor inconsistencies, but anything significant should make you reconsider your identities.

  • Take special note of locality and substrate

  • Often, you will find an entry that seems to closely match your unknown, but does not occur in your part of the country. Or, your unknown was found on wood but the closest match is only found on soil. This disagreement is no different than failing to match some other key feature, and you should take it seriously. There are many widely distributed mushrooms that have no specific locality. Equally there are plenty of versatile mushrooms that can act on a variety of substrates. But if the guide states a specific locality or substrate, you should consider it carefully.

  • Remember there are far more species than there are entries in your guide

  • It is a common mistake by beginner foragers to page through their field guide, pick the closest match, and settle on that. If you are truly interested in the identity of your mushroom, and especially if you are collecting for the table, you need to accept that your guides may simply not describe your unknown. If you go by the Arizona Mycota Project list, there have been around 1300 mushroom producing fungal species described for Arizona alone. Does your guide contain 1300 entries? As I'm sure you realize, field guides try to describe the most common, edible, and interesting species, and are far from complete.

  • Read the comments, if there are any

  • Depending on the detail your guide goes into, the entries may contain special information that can be very useful in your ID process. Typical special comments may include:
    - Lookalikes
    - Sister species that occur at different localities
    - Sister species with slightly different characters that don't merit their own entry
    It is not uncommon to find an entry for a common mushroom that comes close to your unknown, but does not occur in your area, or fails to match a particular key feature, yet in the special notes a sister species that matches your unknown is described.

  • Compare the photos, but with caution.

    We are visual creatures. You can often get a good idea of possible matches just by browsing your guide and comparing similar entries to your photos. Yet, there is inherit weakness in trusting too much in your guide's photos. The appearance of a mushroom can depend greatly on environmental conditions such as recent rain, humidity, etc. And many species are well known for their variability in color and size. Note that color and size were not included in the identification section of my website.

  • Use the internets!

    As you have certainly deduced after visiting this website, I include many links to informative websites here. There are some excellent online resorces to help with identification:

    Michael Kuo's Mushroom Expert website goes into great detail and covers a wide array of species. It is probably the most comprehensive ID website on the web.

    Michael Wood and Fred Steven's California Fungi website is a detailed, comprehensive resource, but contains many species that do not occur in Arizona, and lacks some species that do.

    The Canadian Forest Service's Matchmaker is focused on gilled mushrooms of the Pacific Northwest, but is still a great tool and is simply fun to use. Matchmaker can be useful in identifying wide ranged Western mushrooms, or those which are widely distributed across North America.

    Finally, it never hurts to simply do a google image search if you have narrowed down your unknown to its genus.

  • Use your intuition!

    As you become more familiar with the taxonomic groups of mushrooms in your area, you will be able to make educated guesses on the family, genus, and maybe even species of your unknown. If you think you recognize the group it belongs to, page through your guides and search the web. Even it you're wrong, you may find a closer match in the process, or find a lookalike described in the comments.