Boletus species 01

[ Basidiomycetes > Boletales > Boletaceae > Boletus . . . ]

by Michael Kuo

Note 9/28/04: A preliminary DNA study of this mushroom by Swedish and British scientists indicates genetic affinity with Boletus aestivalis, a European species whose documentation in North America is debatable (see Both, 1993). Results, however, are incomplete and as yet unpublished.

I find this bolete regularly in Douglas County, Illinois, under oak and hickory in mid-June. It reappears consistently each summer, and has done so regularly over a period of seven or eight years. In dry years, one or two will appear; in wet years I have collected many. It is a wonderful edible, indistinguishable from Boletus edulis in consistency and flavor.

But it is not Boletus edulis, or at least it is not the form of Boletus edulis that is commonly described (and which I have found in Finland and Colorado), or the softer-capped, less red form (which I have found in Michigan, Pennsylvania, and Illinois). Its shape and stature are edulis-like, and its reactions to ammonia and KOH parallel those of Boletus edulis, but its cap is creamy white to light tan, and it is consistently cracked up and broken, regardless of weather conditions. It is also not Boletus variipes, another good candidate for an identification match, since it is not as prominently reticulate, its reactions to ammonia and KOH are different, and its spores are too small.

Description:

Ecology: Apparently mycorrhizal with White Oak and/or Shagbark Hickory; growing gregariously (rarely clustered); June; Douglas County, Illinois.

Cap: 7-18 cm, convex in the button stage, expanding to broadly convex in age; dry; with the texture of well-worn leather; more or less smooth, but soon breaking up and developing deep and prominent cracks; whitish to very pale tan, becoming pale brown in age; not bruising or discoloring; the margin inrolled when young, splitting with age, typically without a sterile projection; the cuticle not really much of a cuticle at all, at least in the way the Boletus edulis cuticle, for example, is clearly defined and separate.

Pore Surface: Whitish to dirty gray when young; becoming pale buff, then olive, then brownish; young pore surface bruising ochraceous to brownish--a sort of watery and darker version of the pore surface color--older surfaces bruising brown or not bruising; the pores "stuffed" until the mushroom is quite old; tubes colored like the pore surface, extending to 12 mm deep; eventually free from the stem.

Stem: 4-10 cm long; 2-4 cm. thick at the apex; swollen towards the base, becoming more or less equal; finely reticulate (over the whole stem or, more often, only near the apex); the reticulation typically white but occasionally brownish; usually developing fissures and "peeling" sections; whitish; sometimes appearing to stain brownish when handled; solid.

Flesh: White; thick throughout; not staining on exposure.

Odor and Taste: Pleasant.

Chemical Reactions: Cap surface orangish tan with KOH, orangish tan with ammonia; flesh negative with KOH, negative with ammonia.

Spore print: Olive brown.

Microscopic Features: Spores 10-13 x 3-4 µ; smooth; subfusiform.

REFERENCES: Unnamed putative taxon. (Described and illustrated in 100 Edible Mushrooms--Kuo, 2007.) Herb. Kuo 06269601, 06210201, 07220319.

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Kuo, M. (2004, November). Boletus species 01. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_sp_01.html