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Boletus edulis

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

by Michael Kuo

Boletus edulis is a well known European bolete that grows under spruces and, depending on how the species is defined, other conifers and even hardwoods. It is a large mushroom with a greasy to tacky, bald, brown cap and a meaty, swollen stem that features fine reticulation. The pore surface is initially white, with "stuffed" pores--but as the mushroom matures the pores become more visible and the pore surface becomes greenish yellow. The flesh does not change color when the mushroom is sliced, and its surfaces do not bruise on handling.

Whether or not Boletus edulis occurs in North America is up for debate. Mushrooms meeting the general description above can be found in diverse North American ecosystems. However, molecular research has begun to reveal potential differences in ostensibly identical "Boletus edulis" collections in North America and Europe--for example, see the preliminary survey of boletes by Binder & Hibbett (2004), in which "Boletus edulis" collections line up into clearly distinct groups (type the accession numbers into the search box at GenBank if you're interested in seeing where the collections were made).

REFERENCES: Bulliard, 1780. (Fries, 1821; Saccardo, 1888; Moser, 1983; Breitenbach & Kränzlin, 1991; Hansen & Knudsen, 1992.)


Boletus edulisItaly

Boletus edulis

Key to 12 North American edulis-like Boletes  

The key below sorts out 12 edulis-like North American boletes. In many cases, North American names have been established (at least on the basis of morphology)--but in some cases I have had to refer to European species names. Don't be surprised if your edulis-like bolete doesn't seem to fit in; this species group is in desperate need of an extensive study!

1.Found under hardwoods.

1.Found under conifers.

2.Found under live oak or other hardwoods (including madrone and tanoak) on the West Coast.

2.Found under oaks and other hardwoods east of the Rocky Mountains.

3.Cap dark brown, with a whitish bloom when young; cap cuticle clearly differentiated.

3.Cap pale (nearly white), without a bloom; cap cuticle poorly differentiated.

4.Mature pore surface yellow to brownish yellow, without green or olive shades; stem flushed with liver brown, at least in part; ammonia turning green on cap and stem surface.

4.Mature pore surface greenish yellow to olive yellow; stem sometimes brownish to reddish brown but not flushed with liver brown; ammonia not turning green on cap or stem.

5.Cap medium brown to yellow brown, often wrinkled when young and very finely patchy when mature; ammonia turning purple on cap surface.

5.Cap variously colored and textured; ammonia not turning purple on cap surface.

6.Cap greasy to tacky, bald, cinnamon to orangish brown.

6.Cap dry, leathery or finely velvety (at least when young), variously colored.

7.Appearing in fall; cap brown to grayish brown (dark brown in variety fagicola), very finely velvety when young, often becoming finely patchy in maturity.

7.Appearing in summer; cap pale brown and leathery, sometimes becoming cracked with maturity.

8.Found in western North America.

8.Found east of the Rocky Mountains.

9.Cap pale (nearly white); cap cuticle poorly differentiated.

9.Cap more highly colored; cap cuticle clearly differentiated.

10.Cap reddish to reddish brown; found under spruces and firs at high elevation in the Rocky Mountains after monsoon rains.

10.Cap otherwise colored; found elsewhere.

11.Appearing in spring (adjusted for elevation) in the mountains of California and the Pacific Northwest; often growing gregariously or in clusters.

11.Appearing at other times of the year in diverse ecosystems; rarely growing in clusters.

12.Appearing in fall and winter under Bishop pine and other pines in coastal California; mature pore surface brownish to cinnamon brown.

12.Appearing in various locations and seasons; mature pore surface olive brown.

13.Cap with a whitish bloom when young, becoming bald; stem white or slightly brownish with age; appearing in montane Oregon and Washington.

13.Cap velvety to finely hairy; stem brownish; appearing in various California and Pacific Northwest ecosystems.
Boletus fibrillosus
in Theirs, 1975

14.Appearing under loblolly pine and other pines along the Gulf Coast; cap dry, reddish to reddish brown; stem brownish to reddish brown, not usually swollen.
"Boletus pinophilus"
in the sense of southern authors
(see note)

14.Appearing under spruces and pines in northeastern North America, perhaps as far south as North Carolina; cap greasy to tacky, orangish brown to cinnamon; stem white (perhaps faintly brownish with age or handling), usually swollen, at least when young.

(References used for this page can be found in the reference list for boletes.)

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Kuo, M. (2010, March). Boletus edulis. Retrieved from the MushroomExpert.Com Web site: