Observation 60530: Lactarius deliciosus group

When: 2010-12-09

Collection location: Foster City, California, USA [Click for map]

Who: Tom (LanLord)

No specimen available

Although I never did detect any latex on these specimens, it had the Lactarius look and smell.

These were growing at the base of some ornamental (knobcone) pines in a parkway.

Many were growing with grass strongly attached to the caps.

I’m not sure if the flesh was orange or immediately stained orange upon being cut. But it was very bright orange.


These have matured now, there is absolutely no latex, even after scratching a section of gills, nothing is exuded.
These have matured now, there is absolutely no latex, even after scratching a section of gills, nothing is exuded.
These have matured now, there is absolutely no latex, even after scratching a section of gills, nothing is exuded.
These have matured now, there is absolutely no latex, even after scratching a section of gills, nothing is exuded.

Proposed Names

-13% (5)
Recognized by sight
98% (8)
Recognized by sight: Too much green staining for Lactarius deliciosus s.str.

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

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Scratching the gills
By: Irene Andersson (irenea)
2010-12-16 07:14:11 CST (-0500)

is usually not the best method to see the latex. Cutting across the gills with a very sharp knife works better.
You can se plenty of it in picture 125643 where you did cut through the cap and the gills.

texture of the stipe
By: Tom (LanLord)
2010-12-14 20:02:53 CST (-0500)

It was surprisingly tough. The entire mushroom was very solid, almost to the point of being rock hard.

Looks like L. deliciosus …
By: Daniel B. Wheeler (Tuberale)
2010-12-14 02:22:42 CST (-0500)

but have reservations from the second photo showing the stipe cut near the base: have never seen that coloration before in L. deliciosus. Can’t say whether it is unusual or not, because I’ve never sliced at that location. Cut section looks almost like a pudding texture. So I’ll keep my vote to myself, having not had any insight into the DNA of this group. I’ve always heard L. deliciosus locally from mycologists here in Oregon. Maybe we’re just lumpers?

We need a vote on the voting!
By: Jason Hollinger (jason)
2010-12-12 19:47:44 CST (-0500)

Looks like my “as if” vote on genus has been booted off the island. :) I will amend my ways. Good thing Nathan gave me an artificially high contribution weight!

A shorter comment
By: Johannes Harnisch (Johann Harnisch)
2010-12-12 13:08:05 CST (-0500)

If you don’t like the idea of voting down a correct but less specific Genus name then what about voting down a correct species name because of an unfavorable or incorrect genus name? i.e. Russula deliciosus
seems ridiculous in this case but there are cases such as with that of Clitocybe/Lepista nuda for instance and some may even be placed in two genus because of an undecided classification,
In my opinion unless some one comes up with some thing really a whole lot better
the way it is working now seems to be good, and like some one has said don’t vote “as if” on a correct Genus that is less specific even if the species has been decided and voted “Id’ call”

The idea of voting independantly on the species and genus names
By: Johannes Harnisch (Johann Harnisch)
2010-12-12 12:48:55 CST (-0500)

…presents and interesting thought,
would it be plausible to take for instance one name and split vote ie some thing like this
Lactarius deliciosus and below the name “Lactarius” there could be a voting area specifically for The Genus and then below indigo there would be another one for the species and they could be voted on independently.
the problem with that is that there would be double the amount of time spent voting which would already be increased by more choices….
I am not too sure it would work great… I don’t really mind the current way of voting species names.

Another interesting thought is that some species can be (in other instances) placed in more then one Genus which could promote some interesting things like have a species with two genus both rated “id call it that”

Not to pick nits but…
By: Nathan Wilson (nathan)
2010-12-12 10:18:41 CST (-0500)

In general I agree with Jason’s comment, but I disagree with ever voting “As If!” on a genus name you consider correct. This is a great case to explain that. The names that have been proposed include a single species name (Lactarius deliciosus), an informal group name (Lactarius deliciosus group) which in this case is probably a polyphyletic group of species all within the genus Lactarius, and a genus name (Lactarius sp.). The only one of these I would actually consider likely to be “wrong” is L. deliciosus. From the perspective of most professional taxonomists, the ‘best’ name in this list is probably Lactarius sp. since it is the best scientifically defined term that is known to be “correct”. Irene also mentioned the sectional name, Lactarius sect. Deliciosi that would be even “better” from this perspective. Personally, I prefer the group name because it conveys the most accurate information about the observation itself, but I certainly can’t fault someone for calling it Lactarius sp. or Lactarius sect. Deliciosi.

Jason’s case of Lichen sp. is different since that’s an invalid scientific name being used for a specific purpose since we haven’t been able to implement all the features we want.

This has been a very interesting set of comments
By: Tom (LanLord)
2010-12-12 09:23:05 CST (-0500)

Thank you all. Very informative.

By: Jason Hollinger (jason)
2010-12-11 23:25:18 CST (-0500)

Sorry to pile on Tom’s poor, unsuspecting observation, but since the discussion has started…

Nathan: I suspect I was toying with the possibility of independently scoring each taxonomic level. Thus genus would get a score, and within each genus the species would get scored. In this case, only one genus has been proposed (in all three proposed names), so it’s a no-brainer. The only effect scoring this way would have in the present case is that the generic naming (“Lactarius sp.”) would have no effect on scoring between the two specific namings. One can certainly make a good argument that this makes comparisons between generic and specific names make more sense — the consensus calculator would never compare them at all! How consensus gets calculated in practice if multiple genera are involved (sometimes even kingdom is uncertain!) is another matter altogether.

But going with what we have: I have found that referring to Nathan’s rule of thumb as a mantra when deciding on votes helps a lot: Which of the proposed names is the best name to apply to this observation? In this case certainly one of the two specific names is correct, so in all cases “Lactarius sp.” is not the best name, so I’d vote it low, perhaps even “as if”. That way it forces the consensus calculator to choose one of the two specific names.

Now, if on the other hand, there is some chance it is a third species not even proposed, then Lactarius sp. suddenly has a chance of being the best name of the three proposed. Then vote it higher: “could be”, say. That way if enough people vote against the other two names, the consensus calculator will choose the generic one as the “safer fallback”.

It is my hope that people will not take offense to “as if” votes on their namings, especially generic namings (e.g., Lichen sp.). Voting “as if” on “Lactarius sp.” does not in any way imply it was foolish to propose that name in the first place! It just expresses great confidence in the other names.

But how would we make these heuristics more intuitive? There’s a question…

“Could Be” vs. “Seems Reasonable”
By: Nathan Wilson (nathan)
2010-12-11 08:17:30 CST (-0500)

This gets into the math of how we are currently calculating the “Community Vote”. This gets a bit technical, but since Alan asked…

Right now each of the phrases have different point values ranging from 3 (I’d Call It That) to -3 (As If!).

In addition, each user gets a weight to their vote. Roughly speaking the weight is a number of votes. Every user the log base 10 of their contribution score votes. In addition, the original observer gets an extra vote since they actually saw it. For example, a vote from me on this observation would currently get a weight of:

log10(75940) = 4.88

A vote from Tom (LanLord) would get a weight of:

1+log10(16653) = 5.22

Then for a given naming, these values get combined to come up with a weighted average. So in this case imagine that Tom says “I’d Call It That” and I said “Could Be”. This would result in an overall vote of 1.85:

(3*5.22 + 1*4.88)/(5.22 + 4.88 + 1) = 1.85

The extra +1 gives extra weight to namings that have more votes (since the 1 makes less and less of difference as the number of votes goes up). The range of possible values remains between -3 and 3 so the percentage is calculated from that. In this case it would be: 62%. If I had not said “Could Be” the final percentage would be: 84%.

This is fine if my saying “Could Be” is to cast some doubt on this naming, but if my goal is simply to say I don’t really know this species, but this name “Seems Reasonable”, I should actually be increasing the value, but not as much as when I say “I’d Call It That”. In comparison, if I were to have “I’d Call It That”, then the final percentage would be: 91%.

My idea with “Seems Reasonable” would be to reduce the weight of my vote. Say we take it to mean that I just give 1 vote. In this case, the final percentage would be: 86%.

Similarly, the “Correct, but Less Specific” vote could essentially change the weight of the vote. I seem to remember Jason having another thought about how to handle the “Correct, but Less Specific” case, but I can’t dredge it up from memory at the moment.

Lactarius deliciosus group
By: Irene Andersson (irenea)
2010-12-11 07:08:27 CST (-0500)

is not just one taxon, it includes several species or forms with many existing variety names. Some are synonyms, others difficult to interprete and/or delimit.

I think “Lactarius deliciosus var areolatus A.H. Smith” is a “Could be” on this particular observation (cap colour orange and staining greyish green, latex orange and staining the context vinaceous red), but using that name would make the epithet “deliciosus” polyphyletic, not reflecting new taxonomy that is supposed to be based on DNA and true relationships.

Unfortunately, taxonomy and naming species is a slower process now than the DNA studies, and more controversial..

A shorter comment…
By: Angelos Papadimitriou (Aggelos(Xanthi))
2010-12-10 20:17:32 CST (-0500)

Thanks everyone for your answers.

That anyone would vote against L. deliciosus because that is a European name, not applicable to a morphologically very similar taxon of North America, never crossed my mind, as it was something I didn’t know about. I thought L. deliciosus was a cosmopolitan species, just like, say, Amanita muscaria or A. phalloides. I believed those negative votes meant the voters thought it was a different, though very close, already known and described species, so I wrote what I wrote. My bafflement was made worse by the fact that I found many more observations from various US locations named L. deliciosus posted here on MO with generally high votes. Actually, one of them (21111, posted last year) was by Alan himself, who calls his finds L. deliciosus and gives this name the highest vote!

But what is to be done until someone properly describes this north American counterpart of the European L. deliciosus and gives it a proper name of its own? Will that taxon have to be called (a) “Lactarius [in the] deliciosus group” until that day dawns? Wouldn’t something like “Lactarius deliciosus (North American form or just NAF)” be less vague?

Nathan, I think your short phrases are much better than just a set of numbers (numbers are impersonal and do not interact well with most people). I find it a lot easier to make my choice with these phrases than with numbers. A catch with phrases, however, is that you usually don’t have to think much before choosing. I can’t think of any other phrases I’d like to use now, but the whole thing works quite well as it is.

I’m sorry a misunderstanding, though justified imo, caused all of this and I hope we have all profited somewhat from the discussion.

By: Alan Rockefeller (Alan Rockefeller)
2010-12-10 14:44:03 CST (-0500)

Nathan, how would “Seems reasonable” be different from “Could be”?

Angelos, I voted against Lactarius deliciosus because that is a european name and the north american material is a different undescribed species. I do not consider “Lactarius deliciosus group” to include other described species of Lactarius.

Handling names and what votes you can make…
By: Nathan Wilson (nathan)
2010-12-10 12:30:45 CST (-0500)

Angelos raises an issue that has been simmering for a while with Mushroom Observer which is how to handle names that are ‘correct’ (this is clearly a species of Lactarius), but not as specific as some of the other options vs. names that are ‘wrong’ (this is clearly not an example of Lactarius indigo).

Jason and I have had multiple conversations about this and have not found a completely satisfying solution to this problem. Personally, I use “Could Be” for this purpose. Thus I’m not saying it isn’t a Lactarius. This seems like a reasonable convention, but it is difficult to communicate or “enforce”. The problem with this solution is that it interferes with the other potential use of “Could Be” where I’m really not sure whether the name applies or not.

The other related problem is confidence. Personally I don’t like using “I’d Call It That” for a species that I don’t know well. However, using “Promising” or even “Could Be” has bad effects on the overall rating for a given name. I have been thinking about adding a separate dimension of confidence for a name, but the UI is a bit tricky. Personally I like the short phrases since I think people find it more meaningful than a numeric scale (even though that’s what’s happening under the covers). The phrase I’ve thought about adding is “Seems reasonable” to capture the idea that I don’t know a species very well, but the proposed idea seems reasonable.

I’d love to know what people think about these problems. Do you like the use of short phrases over a numeric system? If so, are there other phrases you wish you had? I’ve been wondering about handling the genus case. Something like “Correct, but less specific” might work for that. There are some mathematical challenges behind deciding which name is the “consensus”, but in my view that can be worked out later.

A short comment
By: Irene Andersson (irenea)
2010-12-10 12:04:18 CST (-0500)

I have chosen to follow the nomenclature used by Nuytinck, Verbeken & Miller in their study of Lactarius sect. Deliciosi (= “Lactarius deliciosus group”):

The fact that someone has used the name deliciosus with a variety name on it for a particular species, doesn’t necessarily mean that it IS a variety of deliciosus. The study by Nuytinck et al with DNA comparisons between european, american and other taxa in the study, shows that the american “deliciosi” form a clade of its own, and even a species like quieticolor is closer to deliciosus.

I can’t exclude the possibility of a deliciosus form occuring somewhere in North America, though – particularly not if it’s found in the eastern or northern parts.

Is Lactarius deliciosus really so unlikely?
By: Angelos Papadimitriou (Aggelos(Xanthi))
2010-12-10 11:08:23 CST (-0500)

First of all, I understand that when someone votes against, for example, Lactarius sp., that is not supposed to mean they reject the possibility of the mushrooms being a Lactarius species, but that they do so in order to move on to something more specific, right? Ok, it’s rather obvious, but still it’s somewhat oxymoronic! Couldn’t there be another, less contradictory way of expressing the same idea?

Now, regarding the rejection of Lactarius deliciosus, I believe the idea is that the mushrooms in the pictures are something close to, but not the same as, L. deliciosus. And does the “Lactarius deliciosus group” include only varieties/forms of Lactarius deliciosus or is it taken in a broader sense to include similar species, as for example L. semisanguifluus, L. salmonicolor, L. deterrimus? Again I think that the latter is the case.

In any case, I believe we can exclude the following because of their habitat, at least according to most authors/books:
-L. semisanguifluus (Pinus silvestris)
-L. salmonicolor (fir, mainly Abies alba)
-L. deterrimus (spruce [Picea])

So, excluding also all the other species of section Dapetes (subsections Sanguifluini and Deliciosini) which are clearly different (such as L. sanguifluus/rubrilacteus, vinosus, hemicyaneus, quieticolor), the only species that remains is, if I’m not mistaken, Lactarius deliciosus with its various varieties and forms. According to Index Fungorum, there are about 30 varieties and forms of L. deliciosus, most of which are rather obscure, absent from most literature, or of only nominal importance. Thus, if you find no fault with my above expressed arguments, what else is left than Lactarius deliciosus, so be it in one of its varieties/forms?

About Greening

And I come now to the tricky issue of the (not(?)) greening of L. deliciosus. It’s true that this species’ tendency to spot green or acquire greenish shades is slight, at least in relation to others, esp. L. semisanguifluus. It is not inexistent, however. On the contrary, it can be quite intense sometimes, though rarely. In the literature I’ve found the following:

-“Cap… sometimes with or entirely blotched green”, Mushrooms Demystified, by David Arora, second edition, 1986. And, speaking of this Arora’s famous, especially in America, book, will you please have a look at color plate No 3 for L. deliciosus (right after page 464). How about some greening there?!

-“Cap… scarcely greening. Gills spotting green.”, Mushrooms & Toadstools of Britain & Europe", Courtecuisse & Duhem.

-“Cap… becoming tinged greenish in places”, Roger Phillips’ Mushrooms and Other Fungi of Great Britain & Europe.

-“Chapeau… verdissant plus ou moins” [= “Cap… greening more or less”], E. Gerhardt, Champignons (French edition).

-“[Colore della] cuticola [del capello]… talvolta un po’ verdastro nelle lesioni.” [=[Color of the] cuticle [of the cap]… sometimes a little greenish in lesions [i.e. injured places]], M.T. Basso, Lactarius.

-“Cap… often spotting green in age and in places eaten by snails and slugs”, F. Kr’a’nzlin, Fungi of Switzerland, (vol. 6, English edition) Russula and Lactarius.

-“Chapeau… marque’e de taches vertes assez de’limite’es surtout vers les bords” [= “Cap… spotted with quite delimited green tints especially towards the border”], A. Marchand, Champignons du nord et du midi, vol. 6.

It seems that, despite the lack of a general consensus on the degree of greening of L. deliciosus, its (often not so slight) greening is a fact. In my own personal experience, L. deliciosus does green in age and when injured, though mostly only slightly; otherwise I can’t have seen more than a few dozen fruitbodies of this species in my life! And, if you ask me, the greening I see in the photos here I’d call slight. Perhaps the fact that all of the basidiomes in the last but one photo do have green shades and spots makes it look like it’s too much, but in my opinion it isn’t.

Another thing that speaks for the greening of the species is the formation of var./forms such as L. deliciosus f. virescens (= greening), var. aeruginosus (blue-green like copper rust), and var. atrovirens (= becoming dark green).

Reddish/Orange-red Latex

Perhaps one other reason why there has been such extended rejection here of L. deliciosus is the reddish/orange-red latex we can see in two of the photos where the basidiomes have been sectioned. Despite the notion that its milk (and thereby colored flesh) are supposed to retain their initial carot-orange color, even if hours may have passed, this is not always the case. Many basidiomes’ latex will tend to become darker (towards the color red) with time or will even be so colored from the beginning. Those who don’t feel comfortable with that, will call such finds L. deliciosus f. rubescens. If you like, I could propose that as a new name for this observation.

Overall, Lactarius deliciosus is a polymorphic species and I don’t think we should be dogmatic in interpreting it, nor should we rely in what one or two books or authorities tell us about it.

Please write about any objections you may have to what I have argued for. I’d be particularly interested to know what other species, or variety/form for that matter, you would propose in place of L. deliciosus.

I apologize for the fatigue this long “comment” must have caused you, but I thought it was worth sharing with you all this information I got from many sources, information which some of you might not have ever come across. Thanks for reading.

Why reject Lactarius deliciosus?
By: Angelos Papadimitriou (Aggelos(Xanthi))
2010-12-09 21:04:07 CST (-0500)

This Lactarius looks very much like Lactarius deliciosus, so it’s rather surprising that anyone would vote so categorically against this possibility! I would be very interested to know the reasons for this rejection.

L. deliciosus seems right
By: Tom (LanLord)
2010-12-09 20:50:50 CST (-0500)

It had the green staining on the flesh and gills.

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