Observation 209131: Boletus luridus Schaeff.

When: 2015-07-07

Collection location: Cook Forest State Park, Pennsylvania, USA [Click for map]


Who: Scott Pavelle (Scott Pavelle)

No specimen available

This is the one that has us all stumped. We found it on Friday, July 3rd, 2015 on a trip to Cook’s Forest. It was under a mix of old growth pine and hemlock, but there were some unidentified leafy trees scattered through the area so I can’t swear to any specific association. The mushroom was in prime condition, neither particularly young nor decrepit.

At first I thought subvelutipes because the pores stained instantly blue-black (one photo shows a letter “S” taken this morning, which happened so fast I could not get the camera up to document it over time). But then I saw that the stem either was (or stained) bright crimson before turning blue, and then black, and then fading overnight to brown. (I’ve tried to catch that time lapse with several photos of the changing stem that were taken this morning).

Note that the context is white, only stains a little bit blue, and stains so slowly that I’m thinking the blue could have come from smearing since the cap was pores-up when sliced. I am totally confused. All the lookalikes I’ve found in the books are supposed to have a yellow context before they quickly stain dark blue. So this characteristic rules both of those out.

Note that the netting on the stem is red.

You’d think something with so many unique characteristics would be easy to identify but I can’t seem to figure it out. Suggestions would be appreciated.


White context that did not stain. Cool red netting.
Cap a nothing tan color. Stem red when cut, then indigo blue, then black (here), and then fading.
Stem bright red when cut.
Good overall view. Could the red be just at the bottom of the stem?
Good overall view. Could the red be just at the bottom of the stem?
Stem about 10 seconds after being cut
Good shot of the context. WHITE, not yellow. It never did stain. Pores yellow by the context & red underneath?
I think the blue on the context was smearing. Cap was cut from the pores down.
Good view of halved mushroom.
Red stem before the staining set in.
Stem on the morning after it was cut. Staining faded.

Proposed Names

-5% (4)
Recognized by sight: Stem is a perfect match, but the context is wrong.
Used references: Bessette @ p. 148 (“burgundy red areas in the base” a big positive, but another that’s supposed to have instantly-bluing yellow context)
-28% (1)
Recognized by sight: The white, non-staining flesh and bright red stem context seem to rule this out. Those inconsistencies were why we bothered to bring it home.
Used references: Bessette p. 167 – subvelutipes has bright yellow cap context that quickly stains dark blue.
-28% (1)
Recognized by sight: Same as subvelutipes and rhodosanguinus – discolor’s supposed to have yellow, quickly-staining context but instead has bright white context that stains irregularly, if at all.
14% (4)
Recognized by sight

Please login to propose your own names and vote on existing names.

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
A clinical trial actually sounds like a good idea – and a viable one.
By: Scott Pavelle (Scott Pavelle)
2015-07-08 11:50:15 CDT (-0400)

Red-mouths (subvelutipes) are pathetically common in my area. It shouldn’t be too hard to find a patch of similar size that are probably fruits from the same mycellium. Or at the worst two patches that are near neighbors.

Say we find 5. I could do a set of photos/color observations when picked with a stopwatch to get a basically reliable estimate of the elapsed time; then a duplicate test a few hours later at home; a third the next morning after sitting out overnight; a fourth the next morning after a night in the fridge; and a fifth after two nights in the fridge. That should provide a decent test to isolate the effects of time and refrigeration on bluing in that particularly responsive species. As a bonus, it might be possible to note color changes in the yellow context (at least when the bluing is slow enough to get a photo!).

Any suggestions for a change in the experimental method? The best approach would be to set the phone on “video” to record the various tests, which would make a stopwatch irrelevant. But it could be hard to post. Will this site handle videos of that kind? If not, how could I share them?

For that matter, I’d be very interested to see other people’s results if anyone can construct a similar test. If there turns out to be a consistent pattern it would make post-walk identification that much easier. And it would be fun to know as a general matter. Surely someone has done this test in a high school or college class somewhere. Has it ever been published? What were the results?

Always work with fresh specimens
By: I. G. Safonov (IGSafonov)
2015-07-07 23:51:45 CDT (-0400)

Most of the notes taking should ideally be done in situ, i.e. at the collection site, and with fresh material. If you have luxury of finding several fruiting bodies at different stages of development, you will have a good idea of how the species ages with regard to such variable things as tissue color and texture/quality, bruising, and macrochemical tests. Naturally, tissue degrades over time, beginning from when you remove specimens from the ground. Once you start to handle them or carry them around in a bag with other mushrooms and subjecting them to temperature fluctuations, this process accelerates, and your subsequent observation of some of the mutable, time-sensitive properties of the species is likely to be distorted and won’t match the info in the literature. Working on bolete identification a day or two after collection is not going to be a productive process by any means – it will present you with many questions and uncertainties and none of the answers.
Looking at the pix of your mature, middle-aged, not “young and firm”, bolete and noting the key morphological aspects, I would expect its flesh to blue, at least to some extent. If you say it didn’t blue, I surely believe you. Keep in mind that the bluing action, which can be highly variable due to a variety of factors even within the same species (including, but limited to, age and weather conditions), alone will not be the defining feature of that you should be hanging you identification hat on one way or another. To me, the fact that the stipe is covered with the conspicuous red reticulation is much more important as it immediately eliminates the vast majority of red/orange/maroon-pored boletes with smooth stipes in Bessettes’ North American Boletes (BRB). Looking at the description of B. luridus in BRB, the stipe may or may not be reticulated, but it’s likely to be more than not. I am not pushing for this ID, and my original vote confidence is low enough to reflect that, but there is not much more to go on because the info is just not there. You might as well call this one Boletus sp. unless you get a DNA sequence and try your luck with the GenBank.
Now, to answer some of your questions:
1) & 2) I think the flesh was already white and marshmallowy when you picked it, which is in line with the fruiting body’s age. In my experience most boletes start out with hard and dense flesh.
3) Mostly covered above. Always cut your boletes from top to bottom, such that there is no smearing from the tubes.
4) Bluing of the freshly cut context in fresh, recently collected specimens is what’s relevant. If you want to understand how storing boletes in the fridge affects the bluing action, you might want to consider enrolling a bunch of species from the Boletaceae for a clinical trial. :-)
5) The short answer to that is “Yes”. For more information, see http://www.fungimag.com/fall-2010-articles/BoletesLR.pdf. If you are a chemist, you will definitely have a good understanding of this publication. :-)
6) The crimson red flesh in the lower stipe is a phenomenon I occasionally encountered in red- or yellow-pored boletes with yellow & bluing context. For instance, the specimen of B. oliveisporus in obs 208605 had that feature (not photographed), whereas in all the other examples of this species I collected before had the usual yellow stipe context all the way to the root. Perhaps, the specimen was waterlogged or was growing in a very wet environment.

Finally, generic and species concepts are not written in stone – they always evolve and become refined over time as more information trickles in from collections made and observed by professionals and amateurs alike. Remember that original descriptions of the vast majority of fungi were frequently written based on a single collection and clearly cannot account for all the genotypic/phenotypic plasticity of a given species. Some identifications will be more difficult than others just because Nature wants to challenge us. :-) Don’t let the conjecture cloud your judgment and always focus on those morphological features that tend to be more consistent and are least likely to change over time.

Very best,


Good observation
By: John Plischke (John Plischke)
2015-07-07 22:27:44 CDT (-0400)

I like all the images showing the features of concern. I think that being in the frig and age both really effect color changes. Old ones often seen to lack color changes and the frig does strange things to colors. I hope to see many more of you bolete pictures on here. Boletes in my area are disappearing. I was back to the spot where we were 2 weeks ago and I only saw 4 boletes and not much else. All the bicolor looking ones in the spots were gone.

The specimen was a bit less than a day old.
By: Scott Pavelle (Scott Pavelle)
2015-07-07 19:06:01 CDT (-0400)

We picked it in the late afternoon, got home too late to examine, refrigerated overnight, and then took photos first thing in the morning after letting it come to room temperature. It was a bit marshmallowy (good phrase!) but not “very”. About what I’d expect for a full grown mushroom that would start to go downhill in a day or two.

Buy you’ve raised some points that are beyond my actual level of expertise so I want to confirm if I’m understanding you right. (In other words, please allow for the inherent curtness of this kind of forum. I’m asking questions, not making some kind of sideways comment).

First, I’ve picked a lot of boletes but I never noticed the context changing color after a night in the fridge. OTOH, I never really looked. How notable is that change? Enough to account for a transition from clear yellow to the kind of bright white in the photos? Or is it a case of something fading a bit from whitish yellow to yellowish white? If the latter, I have to say that these were a very white white.

Second, is that marshmallowy texture purely a function of age? We’ve been having this discussion about local bicolors and whether it’s a function of similar looking species, variation within a species, or just age. In one area the bicolors have a lovely texture that’s almost like a supermarket cheddar, but they also tend to be found young around there and have enormously fat stems. On a recent walk with your buddy JP-3 at a very different site we found a wealth of older bicolors with much smaller stems and a much more marshmallowy texture. Based totally on your experience & impressions, is that more a matter of mushroom maturity or mushroom species?

Third, I really don’t think the context was bluing. As noted in the description, we halved these going from the stem down through the pores and then through the cap. I believe the bluing you see are mostly smears coming down from the pore layer. It certainly did not get more intense over time, though I gave it a good hour just to be sure.

Fourth, I have noticed that an overnight stay in the fridge affects bluing. That’s one of the reasons I let this one come to room temperature before taking it out for study. How profoundly could that stay in the fridge affect the bluing reaction? Is it due to the temperature (in which case warming should have restored it)? Is it a chemical change from the fridge, like some enzyme getting deactivated due to the chill? Is it due to the few hours of aging? And why would the stem continue to stain if the cap experiences such a profound alteration?

Fifth, I’ve also noticed that really old, almost decrepit specimens of subvelutipes blue much less readily than younger ones. Is that the same process? Is there any scientific/chemical knowledge about what causes the bluing reaction and what degrades it, or is this all lore?

Sixth, the white context and lack of bluing are causing a lot of the debate for ID purposes, but I’m struck by some of the other distinctive features that people haven’t commented on. What’s with the crimson stem flesh toward the bottom, and what appears to be a progressively yellower context as you get closer to the pores? I’ve seen that on the outside of the stem many times, but never on the inside! Is that a characteristic peculiar to the luridus family? Or am I just ignorant about this feature?

And finally, another possibility was something in the vermiculosus family. I’ve ruled that out because they are supposed to lack reticulation, and in this stem that’s fairly profound. But I have this nagging sense that reticulation may be one of those features that can vary a lot within species; i.e., you might find a vermiculosus with what looks like obvious netting and a luridus that appears to have none. Especially when you factor in environmental distortions. What are considered the most distinctive features for ruling in and ruling out short of chemical and DNA tests? Is context color more decisive than stem ornamentation? Or pore color? I realize that different features matter more or less with different boletes, but until your comment I’d thought that the basics like context colore were more or less absolute within the parameters you see in the books (i.e., “yellow” might range from pale to amber, but can’t be frosty white).

Thanks in advance.

By: I. G. Safonov (IGSafonov)
2015-07-07 14:32:56 CDT (-0400)

As far as I can see from your pix, the whitish cap flesh did stain blue.
Your specimen is fairly old. The flesh color with age typically turns lighter, and a transition from yellow to white is not unusual in bluing boletes with red pores. I bet the texture of the flesh was very marshmallowy.
I have a hunch that the European B. luridus is not exactly the same thing as the look-alikes from North America. The prominently reticulated stipe of your mushroom points in the direction of the luridus group. The taxonomy of American red-pored boletes is still murky, and little has been done to understand this group from the perspective of molecular phylogeny.

B. luridus looks most likely so far. But…
By: Scott Pavelle (Scott Pavelle)
2015-07-07 13:57:05 CDT (-0400)

MushroomExpert.com says the flesh should be “whitish to yellowish in the cap, and yellow to red in the stem,” which matches. And the stem is a good match. But there’s still a problem with the white AND non-staining cap flesh.

North American Boletes says the context of B. luridus is much more yellow than white, and that it should blue quickly. An unusually good Wikipedia entry also specifies that the cap flesh should be yellow and should stain bright blue. Isn’t context color supposed to be a definitive distinction?

Subluridellus also has bright yellow, rapidly-bluing cap flesh
By: Scott Pavelle (Scott Pavelle)
2015-07-07 13:12:50 CDT (-0400)

See Bessette, Roody & Bessette, NORTH AMERICAN BOLETES at 164. And the mushroom observer page too, which is specific on that point.

Created: 2015-07-07 10:10:54 CDT (-0400)
Last modified: 2015-08-27 19:21:58 CDT (-0400)
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