Observation 9636: Boletus subtomentosus L.

When: 2008-08-18

Collection location: Madison Heights, Pasadena, California, USA [Click for map]

Who: Jason Hollinger (jason)

Specimen available

Very slow bluing when cut, no glands. Spore print rich yellowish brown. Found in lawn. Closest tree is a Lebanon cedar.

Further notes to confirm that it is B. subtomentosus not B. dryophilus: spores are 12 +/- 0.7 × 4.9 +/- 0.3 µ. No oaks in the area (some across the street though). No red tones in the cap.

Further further notes to confirm that it is B.subtomentosus not B. spadiceus: cap just darkens a little when I place a drop of household ammonia on it, I saw no sign of blue, momentary or otherwise.

Note, I’ve seen something very similar to this on a number of occasions within a few blocks of here, and the consensus before was also B. subtomentosus.



Proposed Names

-36% (2)
Used references: Boletes of California on Mykoweb… I have never seen it though so just a suggestion!
87% (1)
Eye3 Eyes3
Recognized by sight

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

Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
By: Jason Hollinger (jason)
2008-08-20 13:30:38 CDT (-0500)

Thanks for your help, guys — both with this bolete (I did the NH~4~OH test), and with understanding the role of indexfungorm and status of Xerocomus. MO seems to be in a weird mixed-up stage where some Xerocomi are recognized, others are not, some are accepted some are not:

These are accepted names:
Xerocomus dryophilus (Thiers) Singer
Xerocomus mendocinensis (Thiers) ??
Xerocomus mirabilis
Xerocomus pruinatus
Xerocomus rubellus (Krbh.) Quelet
Xerocomus silwoodensis Taylor, Hills, Simonini, Muñoz and Eberhardt
Xerocomus spadiceus
Xerocomus truncatus Singer, Snell, & Dick
Xerocomus zelleri Murrill

These are not:
Xerocomus chrysenteron (Bull.) Quél.
Xerocomus ferrugineus (Boud.) Bon
Xerocomus subtomentosus (L.) Fr.

(The last two are my fault — they were misspelled “Xerocomes”, so when I fixed that, I mistakenly deprecated them in favor of Boletus.)

Does someone who knows want to tell me which are wrong? Or is this dangerous territory?

Right in the ballpark — subtomentosus or spadiceus
By: Dimitar Bojantchev (dimitar)
2008-08-20 10:35:58 CDT (-0500)

Looks good. An excellent photograph. In this group only B. spadiceus is your competition for an id. And a tough one. It is not dryophilus, for sure.

Xerocomus or Boletus, doesn’t matter. I prefer Xerocomus because they’re quite distinctly looking and seem to get good support from molecular studies too. Index Fungorum is rather conservative, like it should.

By: Joshua Birkebak (Shua)
2008-08-19 23:04:01 CDT (-0500)

So index fungorum is definitely not the final authority on taxonomy… It is ok but is usually at least a year or two behind…

So Boletus has been know to paraphyletic for a while know… Quite a few phylogenies have shown this! That is where some of these new names for genera have been coming from (e. g. buchwaldoboletus, rubinoboletus, retiboletus, etc.)! The problem is far from fixed but the resurrection (and stricter interpretation) of Xerocomus is another step in the right direction! I am really sorry about “xerocomes” I always try to spell it this way!

So xercomus is not really what it used to be! it is quite restricted from its former sense! Another new genus is Paraxerocomus for the common chrysenteron andrelated species!

For a really good review and explaination see Sutara 2008 here:



What’s going on with Xerocomes/Xerocomus??
By: Jason Hollinger (jason)
2008-08-19 11:35:34 CDT (-0500)

According to indexfungorum, Boletus is still preferred. I can’t find any mention of Xerocomes — surely that’s a typo? And the author for Xerocomus subtomentosus is (L.) Quel. not (L.) Fr. I’m so confused.

Created: 2008-08-19 00:48:49 CDT (-0500)
Last modified: 2008-08-20 13:19:35 CDT (-0500)
Viewed: 110 times, last viewed: 2018-09-16 11:44:55 CDT (-0500)