Xanthoconium separans (Boletus separans)

[ Basidiomycetes > Boletales > Boletaceae > Xanthoconium . . . ]

by Michael Kuo

Here is an attractive and fairly easily identified bolete, found under hardwoods east of the Rocky Mountains. Crucial features include its yellow (not olive) mature pore surface, and the distinctive, lilac-red color of the stem. The young caps are also often colored lilac-red, but they soon fade and become brownish to yellowish brown.

To be certain of your identification, place a drop of common household ammonia on the stem of Xanthoconium separans: the result is a color change to deep blue-green (click here for more information on chemical testing). In its paler forms, Xanthoconium separans might be confused with Boletus edulis, but the latter mushroom does not develop the liver colored hues on the stem, and does not flash green with ammonia.

This mushroom is called Boletus separans in most field guides.

Xanthoconium separans is a very good edible. Like most boletes, it is best when dried and reconstituted.

Description:

Ecology: Mycorrhizal with hardwoods (especially oaks), sometimes with conifers; growing alone, scattered, or gregariously; summer and fall; widely distributed east of the Rocky Mountains.

Cap: 5-20 cm; convex to broadly convex in age; dry; usually somewhat wrinkled; the margin often with a very small projecting sterile portion; color variable but typically lilac-brown or lilac-red when young, becoming yellowish brown in age.

Pore Surface: White when young, becoming yellowish and finally brownish; not bruising; pores circular, 1-2 per mm; tubes to 3 cm deep.

Stem: 6-15 cm long; 1-3 cm thick; more or less equal, or tapering somewhat to apex; solid; smooth or slightly wrinkled; not reticulate in most collections, but faintly to prominently reticulate at times; pale at apex, colored more or less like the young cap overall.

Flesh: Whitish throughout, unchanging on exposure or bruising.

Odor and Taste: Not distinctive.

Chemical Reactions: Cap surface and stem (where liver colored) deep blue-green with ammonia; dingy greenish with KOH.

Spore Print: Brownish to pale reddish brown.

Microscopic Features: Spores 12-16 x 3.5-5 µ; smooth; subfusiform. Pileipellis a tightly packed trichoderm with clavate or subclavate terminal elements--an "epithelium" or hymeniform turf.

REFERENCES: (Peck, 1873) Halling & Both, 1998. (Saccardo, 1888; Coker & Beers, 1943; Smith & Thiers, 1971; Smith, Smith & Weber, 1981; Arora, 1986; Phillips, 1991/2005; Both, 1993; Halling & Both, 1998; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Kuo, 2007.) Herb. Kuo 07299701, 08270206, 08240504, 07060703.

Boletus separans is a synonym. "Boletus nobilis," in the sense of some authors (e.g. Sneel & Dick, 1970), is a synonym. Boletus pseudoseparans is a probable synonym.

Further Online Information:

Boletus separans in Smith & Thiers, 1971
Boletus separans at Roger's Mushrooms

Ammonia

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Cite this page as:

Kuo, M. (2004, December). Xanthoconium separans / Boletus separans. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/xanthoconium_separans.html