Sunday, July 17, 2011

Summer Mushrooms

Specimen found on grass
The weather has been very nice and fortunately we have had a lot of rain in the Rockville region over the last couple of weeks. Naturally, some of my friends are bragging about finding yellow chanterelles (C. cibarius), chicken (L. sulphureus), black staining polypores (M. giganteus) and a variety of boletes in the woods around Rockville. Today I went around the block (as usual) looking for mushrooms growing on lawns in the Rollins Park area. In a short 30 minutes walk I found a large variety of rusulas, Agaricus campestris, Amanita vaginata, Amanita flavorubens, Xerula megalospora, Phallus rubicundus, Tylopilus plumbeoviolaceous and a variety of boletes growing on grass and oak roots. One of the boletes I found looked specially nice (and potentially edible - did not stain when bruised and had a nice yellow pore surface without any tint of red or blue) and therefore I decided to face the challenge and try to identify it for a change.

So here it goes....

Date: 07/17/2011
Location: Rollins Park, Rockville, MD
Habitat: Solitary, growing on grass, under pine trees

Note that it does not stain
Pileus diameter - 51 x 46 mm
Pileus height - 17 mm
Stipe lenght - 55 mm
Stipe diameter at apex - 9.6 x 23 mm
Stipe diameter at middle - 9.6 x 16.5 mm
Stipe diameter at base - 9.6 x 11.6 mm

Pore surface depressing around stipe
Tubes are decurrent
Pileus - brown/red, dry, glabrous, cracked (specially near margin) and revealing light yellow flesh, smell is agreable, taste is mild and non-distinctive. Flesh is yellow and does not bruise.
Hymenium - tubes are bright yellow, depressed around the stipe, evenly distributed. Pores are angular and do not bruise. Tubes are around 6.8 mm long and decurrent (go down stipe 4 mm).
Stipe - central, tapered from base to apex, compressed, reticulated (bold brown reticulation)
Spore print - Not obtained

This seems to be a Xerocomus spadiceus, also known as Boletus spadiceus Fries. This mushrooms is considered to be a good edible which fruits between July and September under conifers and mixed woods.

Some other possibilities which look very similar are B. illudens and B. subtomentosus. Based on the reference provided below, B. illudens' pileus is described as being pale brownish yellow and becoming yellow-brown to pinkish cinnamon and the pore surface as sometimes bruising weakly blue or blue green (the specimen's pileus had tones of red on the cuticle which do not seem to fit with the description and, in my opinion, the pore surface did not stain). The fact that the pore surface does not stain eliminates B. subtomentosus, which stains greenish blue. Furthermore, B. subtomentosus is described as having a pileus that is olive-ochre and that becomes olive-brown with age. I did not observe any tone of green on the cuticle of this specimen.

Last, depending on how you describe the stipe (i.e. “yellow, bright yellow to golden yellow or yellow orange” versus “pallid, pale yellowish, cinnamon to reddish brown”) a few other similar mushrooms could be considered. For this identification I considered the stipe to be pale yellowish…otherwise I would have to call this bolete Boletus sp.

North American Boletes: A Color Guide to Fleshy Pored Mushrooms, page 158.

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