Observation 58355: Paxillus involutus (Batsch) Fr.
When: 2010-11-08
No herbarium specimen
0 Sequences

Growing under a birch tree in an irrigated garden

Proposed Names

91% (2)
Eye3 Eyes3
Recognized by sight: Spore print dull brown. inrolled margin
Based on microscopic features: spores elliptical/ oblong 9-11µmx 5-6µm
28% (1)
Recognized by sight: Maybe undescribed

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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Sorry, can’t check.
By: Daniel B. Wheeler (Tuberale)
2010-11-11 14:22:19 CST (-0500)

Cut the seedling birch tree down about 1988. Haven’t had any Paxillus since. I may try to find a nearby Paxillus with birch in one of my neighbor’s yards to put up today, though.

Your own species
By: Irene Andersson (irenea)
2010-11-11 13:56:23 CST (-0500)

with your own birch – could be Paxillus vernalis then (check for dark reddish brown spore print)

Mycorrhizal only with birch here, Irene.
By: Daniel B. Wheeler (Tuberale)
2010-11-11 13:30:01 CST (-0500)

While we have a lot of other tree species nearby, the only tree I find P. involutus (or is that P. species novum?) with is birch. Sometimes with introduced Paper birch, sometimes with our own native birch species. But ALWAYS with birch.

Darv & Daniel, interesting comments
By: Irene Andersson (irenea)
2010-11-11 03:04:56 CST (-0500)

I have often wondered about Paxillus and their mycorrhiza connection. My impression has been that Paxillus involutus can form mycorrhiza with different trees, but also do well without it. I think Daniel’s experiment confirms that.

A rather recent Swedish study (2009) has shown that some strains of the species had the ability to form mycorrhiza with many different hosts (including Betula and Picea), some with the same hosts (except Betula and Picea), some only with Quercus, some only with Pinus, and some without ability to form mycorrhiza at all.

They also make a comment on their earlier study from 2008: “Recent studies have shown that this fungus consists of at least four genetically isolated lineages, phylogenetic species (PS) I (which corresponds to the morphological species Paxillus obscurosporus), PS II (P. involutus s. str.), PS III (Paxillus validus), and PS IV (not yet supported by any reference material).”

I haven’t been able to read the earlier paper, but I find it strange that they couldn’t include any “PS IV” in the later study.

That’s VERY interesting, Darvin.
By: Daniel B. Wheeler (Tuberale)
2010-11-10 01:55:11 CST (-0500)

I first cultivated what I have been calling Paxillus involutus at my home in 1985 from a specimen obtained at the Oregon Mycological Society Fall Forage. I, in turn, brought it home and dispersed the spores specifically around a seedling birch tree which had just sprouted near the corner of my garage. Why not, I thought? Poisonous, no one will probably will have tried cultivating it before, right? Might prove mycorrhizal fungi are easier to grow than was then believed.

Within a year I had the same material fruiting in my front yard. Had to cut the seedling tree down shortly thereafter, as it started growing rather quickly, and was too close to my house foundation to be a good location. Nevertheless for at least 4 years I had this growing in my front yard. There must be a name already attached to it somewhere, don’t you think?

Can we say it is Paxillus? The material I typically find is quite dark colored, and becomes progressively so. There might even accidently still be some material fruiting nearby. I’m pretty sure Dr. Norvell, who curates the OMS Herbarium, also has dessicata of this material for comparison.

By: Darvin DeShazer (darv)
2010-11-10 00:20:26 CST (-0500)

According to a DNA study at UC Berkeley, the Paxillus involutus associated with Birch are an undescribed species. They are NOT the real Paxillus involutus.

Agreed, Tim.
By: Daniel B. Wheeler (Tuberale)
2010-11-09 20:33:08 CST (-0500)

Your links show definate brown on cap and gills, sometimes quickly bruising brown. I barely see any hint of browning in this collection, though.

Here is a specimen from last year
By: Richard Sullivan (enchplant)
2010-11-09 20:14:20 CST (-0500)

From a different location, This is also very pale and also associated with birch trees.


By: Daniel B. Wheeler (Tuberale)
2010-11-09 20:06:30 CST (-0500)

P. involutus usually has browner gills and stipe, not at all like these photos, even when young. In Oregon, this begins fruiting in September, and often is done fruiting by November (now). Even when quite young the material I’m familiar with has much darker brown gills. I see Darvin has collected this as well, and certainly looks similar to his observation. And the spore work seems reasonable. Maybe more than one variety involved?

Created: 2010-11-09 07:29:45 CST (-0500)
Last modified: 2010-11-10 16:11:10 CST (-0500)
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