Observation 25282: Hydnellum scrobiculatum (Fr.) P. Karst.

When: 2009-09-12

Collection location: Memorial Park, Middletown, Pennsylvania, USA [Click for map]

Who: Fran Sheldon (Serendipity Fran)

No specimen available

Thanks to my friends at Northeast Mushrooms (a Yahoo group), especially Noah Siegel, I am confident of the identification. Here are my observations:

Habitat: Found on mainly oak leaf litter in a mixed hardwood forest, about 50 yards up a slope from a small creek. The largest nearby tree is a red oak. There are also beeches, tulips and two very young maples in the immediate vicinity. No conifers.

Size of patch: The entire patch extends about 15 feet from the red oak and is about 12 feet at its widest.

Clustering: In the patch there are several somewhat round fused clusters, several arcs of singles and doubles, and several random groupings.

Size of clusters/caps: The largest, nicely shaped cluster was about 10 inches across. One of its caps was nearly 6 inches in diameter. The single caps and easily separated doubles were from 2½ to 3½ inches.

Cap grooves and ridges: Closeup photos show the grooves and ridges in the caps, which is apparent on all caps throughout the patch. Older caps, though still ridged, appear slightly flatter. On a dry day, the white margin has a peach-fuzz effect.

Teeth: I was not able to see the teeth with the naked eye. From my enlarged macro photo, I estimate that the individual teeth are about 1/3 mm in diameter. They are sparser towards the margin and denser towards the stem. A cross-section shows the teeth shorten considerably towards the margin.

Stipe: The stipe is firm, but somewhat pliable, but the base is very rigid. When I cross-sectioned the mushroom, the base broke away from the pliable stem under the pressure of the knife. The base felt woody and appears to have roots coming from it.

Taste: Nothing significant noted.


A rain-soaked older cluster. Ruler is six inches.
Cross-section showing teeth shortening toward margin, vase-shaped coloration, and (broken) woody base of stipe with attached “roots”
Teeth descending stipe
Enlargement of teeth
Close up of young cap, after heavy rain, showing deep grooves and pits
Close up of a cap on a dry day, showing the “peach-fuzz” on the margin
There are several arc formations in the patch
The orange ovals roughly indicate the location of the mushroom groupings

Proposed Names

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
By: Noah Siegel (Noah)
2009-09-19 03:54:41 BST (+0100)

you posted it a few weeks ago on MO

ok I posted the wrong one
By: Tom Volk (TomVolk)
2009-09-19 03:24:42 BST (+0100)

I wrote to Sean and he looked and told me I posted an old copy of the key. d’oh!!
Your key is correct. Where did you get that? thanks

By: Noah Siegel (Noah)
2009-09-19 02:47:44 BST (+0100)

What about this?
“24. Fruiting body 9 cm wide or wider, usually highly concrescent; scrobiculate or colliculose at disc; spores 5-6 × 4-5µm, with prominent, round, pointed tubercles; growing under conifer or hardwoods
H. scrobiculatum

24. Fruiting body smaller, up to 5 (7) cm wide; usually gregarious but with concrescent patches; slightly colliculose or scrobiculate; spores 4-5 × 3-4µm, with worn down tubercles appearing almost smooth but appearing uneven; growing under pines
H. concrescens"

Not sure.
By: Tom Volk (TomVolk)
2009-09-19 02:02:04 BST (+0100)

Hi Fran. Thanks for your thorough analysis. This dichotomy from my grad student Sean Westmoreland’s thesis on Hydnellum may help:

15. Fruiting body up to 9.0 cm wide, usually highly concrescent, context up to X cm thick, scrobiculate or colliculose at disc but may be slightly ornamented, spores 5-6 um X 4-5 um, with prominent tubercles………..……H. concrescens

15. Fruiting body smaller, up to 7.0 cm wide, with thinner context, usually gregarious but with concrescent patches scattered, slightly colliculose or scrobiculate, spores 4-5 um X 3-4 um, with worn down tubercles appearing almost smooth but uneven.. ……………………………………………………………H. scrobiculatum

Judging from the size, this may be H. concrescens.

Created: 2009-09-15 02:22:11 BST (+0100)
Last modified: 2009-09-15 02:22:11 BST (+0100)
Viewed: 225 times, last viewed: 2018-10-16 22:26:00 BST (+0100)
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