Major Groups > Boletes > Boletus

MushroomExpert.Com

The Genus Boletus  

[ Basidiomycetes > Boletales > Boletaceae . . . ]

by Michael Kuo

The mushrooms in Boletus are boletes that do not typically have scabers or glandular dots on their stems. Their spore prints are olive brown to brown (a few species with yellowish or rusty spore prints, often included in Boletus, are officially placed in Xanthoconium but are treated here with Boletus). They have solid stems, and their pores are not typically elongated and radial (as in some species of Suillus). Under the microscope, their spores are not ornamented.

Boletus is the largest genus of boletes, containing over 150 species in North America--though the number of species rather depends on which mycologist you're talking to. Identifying members of this genus to species can be frustrating (though not quite as frustrating as identification in Leccinum), and one is constantly finding mushrooms that do not quite fit any description. This problem is compounded by the fact that the experts keep shifting the whole genus around, dropping out species, adding new ones, and combining others. To have much success with identification, you will need to have fresh specimens representing several stages of development; the mushrooms in Boletus often change their appearance rather drastically as they develop.

Specific identification pitfalls include cap color and bruising or staining changes. In general, color is one of the most unreliable features for mushroom identification (which is why looking at photos in field guides is an unsuccessful way to identify mushrooms!) . . . but with mushrooms in Boletus, one is especially likely to encounter problems with cap color. A mushroom described as having a black cap is not likely to have a white one, of course, but the brownish- and reddish-capped mushrooms in Boletus (which is most of them) are frequently variable in color, and subject to color changes due to weather conditions. As far as bruising or staining goes, you will need to be sure to check such reactions with fresh mushrooms, within 30 minutes of picking them. Waiting too long may produce unreliable results. Finally, do not be surprised if you encounter faint staining or bruising where it should not happen, according to many descriptions.

As far as edibility goes, some members of the genus Boletus are among the best edible mushrooms on the planet. Boletus edulis is collected across the globe; if you have ever had "porcini" mushrooms in a meal, you know how good this scrumptious edible is. There are many members of Boletus that are edible--a few of which are as good as Boletus edulis--and, unfortunately, there are some poisonous species.

 

Boletus auripes

Boletus mirabilis

Boletus ornatipes



© MushroomExpert.Com



Key to Boletus and Xanthoconium in North America


Note: This key is in bad need of revision. The non-dichotomous format is annoying and, with the hindsight of a few years, I see many areas that require different emphasis, fleshing out, paring down, and so on. Don't hold your breath waiting, but I will eventually revise the key completely. Several very good keys are included in the references list, below.


Species of Xanthoconium (a genus defined by the yellowish color of the spore print) are included in this key. Species of Xerocomus (a European genus name sometimes applied to North American mushrooms) are included, but are treated as Boletus species.


  • Pore surface not some shade of red or orange. (1/2)

    Page Four

  • Pore surface some shade of red or orange. (2/2)

      > Cut flesh in cap or stem staining bluish to blue on exposure. (1/2).

      Page Two

      > Cut flesh in cap or stem not bluing on exposure (though the pore surface may bruise blue). (2/2).

        ° Stem reticulate on mature mushrooms, over at least the upper portion. (1/2)

          ~ Stem orange yellow, not bruising; cap surface flashing faintly slate blue with ammonia; cap color bright orange-yellow; taste not distinctive or slightly acidic. (1/3)

          Boletus auriflammeus

          ~ Stem rose to red, bruising brownish to olive; cap surface yellowish olive with ammonia; cap color dull red, becoming reddish orange; taste not distinctive. (2/3)

          Boletus carminiporus

          ~ Stem pale to pinkish tan or grayish olive, bruising olive to brownish; cap surface flashing pale slate or staining blue with ammonia; cap color whitish to grayish, becoming pinkish tan; taste mild or bitter. (3/3)

          Boletus firmus
          At Macrofungi of Costa Rica

        ° Mature stem not reticulate. (2/2)

          ~ Stem smooth, with bright yellow basal mycelium; cap color dull pinkish tan; taste very bitter. (1/4)

          Chalciporus piperatus

          ~ Stem smooth, pale to pinkish tan or grayish olive, bruising olive to brownish; cap color whitish to grayish, becoming pinkish tan; taste mild or bitter. (2/4)

          Boletus firmus
          At Macrofungi of Costa Rica

          ~ Stem smooth or with yellow powder, red to orange to yellow, not bruising; cap color yellow to orange yellow; taste not distinctive. (3/4)

          Boletus hemichrysus

          ~ Stem with reddish brown scales, nearly scabrous, yellow under the scales, not bruising; cap color dark olive brown to reddish brown; taste not distinctive. (4/4)

          Boletus morrisii



    References

    Arora, D. (1986). Mushrooms demystified: A comprehensive guide to the fleshy fungi. Berkeley: Ten Speed Press. 959 pp.

    Bessette, A. E., Roody, W. C. & Bessette, A. R. (2000). North American boletes: A color guide to the fleshy pored mushrooms. China: Syracuse UP. 399 pp.

    Binder, M. & D. S. Hibbett. (2004). Toward a global phylogeny of the boletales. Retrieved from the Clark University Web site: http://www.clarku.edu/faculty/dhibbett/boletales_stuff/Global_Boletales_2004_28S.gif

    Both, E. E. (1993). The boletes of North America: A compendium. Buffalo NY: Buffalo Museum of Science. 436 pp.

    Coker, W. C. and Beers, A. H. (1943). The boleti of North Carolina. New York: Dover. 96 pp. (1971 reprint.)

    Grand, L. F. & Lodge, D. J. (1978). Occurrence of Boletus piedmontensis in North Carolina and Georgia. Mycologia 70: 1267-1268.

    Grund, D. W. & Harrison, A. K. (1976). Nova Scotian boletes. Germany: J. Cramer. 283 pp.

    Scates, K. (2004). Trial field key to the boletes in the Pacific Northwest. Retrieved from the Pacific Northwest Key Council Web site: http://www.svims.ca/council/Boletes.htm

    Singer, R. (1945, 1947; reprint 1977). The Boletinae of Florida. Germany: J. Cramer.

    Smith, A. H. & Thiers, H. D. (1968). Notes on boletes–I. 1. The generic position of Boletus subglabripes and Boletus chromapes. 2. A comparison of four species of Tylopilus. Mycologia 60: 943-954.

    Smith, A. H. & Thiers, H. D. (1971). The boletes of Michigan. Ann Arbor: U Michigan P. 428 pp. An online version of this book is available here, at the University of Michigan Herbarium (URL too long for duplication).

    Smith, A. H., Smith, H. V. & Weber, N. S. (1981). How to know the non-gilled mushrooms. Dubuque, Iowa: Wm. C. Brown. 324 pp.

    Snell, W. H. & Dick, E. A. (1970). The boleti of northeastern North America. Germany: J. Cramer. 115 pp.

    Thiers, H. D. (1975). The boletes of California (online reprint of California mushrooms: A field guide to the boletes). Retrieved from the MykoWeb Web site: http://www.mykoweb.com/boletes/index.html

    Thiers, H. D. (1976). Boletes of the southwestern United States. Mycotaxon 3: 261-273.



    Cite this page as:

    Kuo, M. (2002, June). The genus Boletus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus.html