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. 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 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 mushroom you want to identify.
  2. Check a filter that clearly applies. The number of possibilities will shrink accordingly.
  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.

 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?

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.





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. So we bowed to popular demand and stuck this in hear at the bottom. Rankings are based on what’s in the published sources, with the occasional comment from my personal experience.

  • Avoid. The mushroom is a known sick-maker.
  • Bitter. The mushroom is too bitter to eat.
  • Iffy. Usually because the edibility is marked 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).