How to Use the Bolete Filter – A “Synoptic Key”

Tradition creates some kind of “dichotomous” key to identify particular mushrooms. For example, you might start with a particular type of stem feature, and then branch off from there by asking various on-off questions about subsequent features. The problem is, what do you do when the stem has been damaged or it isn’t clear what category it belongs to? Once you lose your place in a dichotomous key it is impossible to go any further.

This approach uses a “synoptic” key, which allows you to limit the number of possibilities by applying whatever features seem to be clear. If the stem features aren’t clear, start with things like the cap color, flesh color, region, and staining characteristics. It’s extremely hard to create a synoptic key on paper because you need to start with a grid listing every possible answer, and then create a transparency for every characteristic you want to use as a filter. I started this project by doing exactly that for the boletes in the greater Pittsburgh area, so you can believe me when I say the costs and the bulk can add up quickly.

Computers make that easy. Hence this site.

The Goal: We’ve built this system to be triage – a preliminary diagnosis – not as a full-fledged identifier. Consult the books and professional websites if you want to get your I.D. down from a few results to a particular species. References are included in each full-description page.

How It Works – Filters Only Remove What’s Impossible: Look at the mushroom in your hand and then go down the list of filters. Click each one that clearly applies. The Filter will remove all mushrooms for which that result is impossible. For example:

Bicolor Boletes typically have a very red cap, occasionally with yellow bits, but can also be brown when age, sun, lack of air intervene. If you click “Primary Cap Color is Red(dish)” Bicolors will remain as one of the choices. But it’s possible to find specimens where the red has darkened or depleted enough for some people to call it brown, or where there’s much more yellow than normal. So the filter was designed to still keep Bicolors as a possibility even if you mark the cap color as Brown or Yellow. Bicolors never get truly pale or truly dark, however, so clicking “Cap is White/Buff” or “Cap is Dark/Black” will remove this mushroom from the list of possibilities.

 Basic Instructions

  1.  Look at the healthy and typical mushroom you want to identify.
    • Note: The database cannot account for all the strange exceptions for things like old-and-rotten, dried-to-a-crisp, infected-with-hypomyces, etc. The keys work for typical features and for unusual features, but not for downright twisted, distorted, or extraordinary features.
  2. Check a filter that clearly applies. The number of possibilities will shrink accordingly.
    • Note: Start with the most unique feature to narrow things down quickly. E.g., lots and lots of mushrooms have yellow pores but only a few can have a cap that’s bigger than your hand, or a stem that’s covered with ridged netting.
  3. Repeat for other filters.
    • Note: It’s better to ignore a filter than to click one (other than color) that could be wrong. Leaving a blank keeps extra possibilities; clicking a false filter removes possibilities that might include your actual specimen.
  4. Once you arrive at a reasonable number of results, look each mushroom up in the text of your choice for a positive identification.
    • Note: Each mushroom also has a “Full Information” page, which includes page citations to various resources, a more thorough description, and how that mushroom reacts to the most common testing chemicals.

The Logic Is Always “And”

For example, If you click both red pores and yellow pores, the results will limit to only those mushrooms for which both of those statements can be true; i.e., it will exclude all species where the pores can never be yellow or can never be red. This is a good trick if you find something like a red-pored species with a ring of yellow (common for certain red mouths that are born with yellow pores that age to red, or vice versa).

This helps for everything but the regional and edibility filters. There is no way to search for a mushroom found in either the Midwest or the Northeast, and clicking both will limit you to only those mushrooms found in both of those regions. As for edibility, there is no overlap so clicking any two of those filters should result in no results. If a particular mushroom happened to be both bitter and a sickener, it would be marked as “Avoid.”

 An Overview of the Filters

The links below go to a fuller description of each filter. What follows is an overview of how they fit in the system:

REGIONAL FILTERS. In what part of North America did you pick the mushroom?

  • Note: All local lists are based on input from experienced local experts and life lists from local clubs. We believe they are going to be “mostly complete” and helpful for any common mushroom in that area, but almost certainly incomplete for rare outliers that your most senior expert has never come across in the past 20 years (and for newer species whose range has yet to be defined). If in doubt use the parent region, such as “South” instead of “Louisiana”. Or don’t click on a region at all.

HABITAT FILTERS. You can’t always tell that your mushroom is associated with a particular tree, but when you can that’s a key feature. Particular associations to oak, beech, pine, larch, etc. are noted in the text descriptions – usually in the “Extra Information” part.

  • Coniferous (“Needle-y”) Trees. For those mushrooms that never grow in association with a deciduous tree.
  • Deciduous (Leafy) Trees. For those mushrooms that never grow in association with a coniferous tree.


  • Note: Don’t sweat the term “Primary Color”. If the species has distinct amounts of both red and brown, it will pass through both of those filters due to the “And” logic described above. We use the word “primary” for situations like the Chicken Fat Suillus (americanus), which always has a yellow cap but can have red spots. The “cap is red” filter will exclude that because spots are not enough.


  • Note: Remember the “and” logic and the fact that pore color tends to change with age.


  • Note: Stem characteristics are often the most important for a final ID.


SPORE PRINT FILTERS. If you take your mushroom home and do a spore print…

  • Olive to Olive-Brown.
  • Yellow to Yellowish Brown.
  • Pink/Red/Purple to Cinnamon Brown.
  • Plain old Brown. This includes all of the “brownish” shades in the categories above, and therefore filters out very few mushrooms.

EDIBILITY FILTERS. Yes, this is bass-ackwards. You identify a mushroom to figure out if it’s edible, not vice-versa. But in play testing it became clear that people often want to create lists of what’s particularly good or bad in their particular region, and it is very useful for people who want to read up on their local bad boys. So we bowed to popular demand and stuck this in at the bottom. Rankings are based on what’s in the published sources, with the occasional comment from my personal experience.

IMPORTANT SAFETY NOTE: There are always going to be exceptions that turn a normally edible species into a sickener for particular people. Allergies and personal sensitivities start that list, but environmental factors (pesticides and other uptake from tainted soil), infection by hypomyces, and plain old bad condition are at least as common. Mushrooms have been called the “poor man’s meat”; if you wouldn’t eat a piece of meat that’s in the same condition as your find, do not eat your find. And remember that you are 100%, totally, exclusively, and in all other ways responsible for any harm you may suffer from putting something in your mouth! Period!!

  • Avoid. The mushroom is a known sick-maker.
  • Bitter. The mushroom is too bitter to eat.
  • Iffy. Usually because the edibility is marked in the books as “unknown,” but occasionally because only a very few people have reported problems.
  • Good. Your standard bolete, anywhere from 10-50% of an edulis.
  • Choice. Lucky you! You’ve struck gold (at least in the minds of some).