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Key to Boletus in North America (Page Five)

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[Pore surface not red or orange; pore surface bruising blue to greenish blue (quickly or slowly), or cut flesh staining blue to bluish on exposure (quickly or slowly); stem not reticulate, or merely faintly so at apex.]


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.


  • Mature cap small, typically no more than 4-5 cm across. (1/2)

      > Mature cap with red shades (brick red, terra cotta, and so on). (1/2)

        ° Found in the Pacific Northwest. (1/2)

        Boletus coccyginus
        At MykoWeb

        ° Found elsewhere. (2/2)

          Growing in grassy areas; pores circular to angular, 1-3 per mm; stem equal (not tapering); cap negative, blued flesh erased with ammonia. (1/6)

          Boletus campestris

          Growing in grassy areas and in woods; pores angular, 1-2 per mm; stem base tapered; cap dull orange, flesh grayish olive with orange outer zone with ammonia. (2/6)

          Boletus fraternus

          Growing "under oak with loblolly pine nearby" in Texas; pores irregular to elongated, larger than 1 per mm; stem base swollen; cap bright reddish brown, flesh negative with ammonia. (3/6)

          Boletus lewisii

          Growing in deciduous woods; pores angular, 1-2 per mm; stem with narrowed base; reactions to ammonia not recorded. (4/6)

          Boletus rubellus

          Growing in deciduous woods; pores angular, larger than 1 per mm; stem equal; cap and flesh bluish with ammonia. (5/6)

          Boletus hypoxanthus

          Growing in mixed woods; pores irregular to angular (almost gill-like near stem), 1-2 per mm; stem with a narrowed base; flesh negative with ammonia. (6/6)

          Boletus subfraternus

      > Mature cap some other color, without red shades. (2/2)

        ° Mature cap olive brown and conspicuously cracked, with red flesh showing in the cracks. (1/3)

        Boletus chrysenteron

        ° Cap yellow to orange yellow, coated with yellow powder; young pore surface running down the stem; mature pore surface reddish. (2/3)

        Boletus hemichrysus

        ° Not as above. (3/3)

          Cap tawny brown, reddish brown, yellow brown, or orange brown; cap bluish with ammonia. (1/5)

          Boletus hypoxanthus

          Cap dull reddish brown to purplish brown; cap bright reddish brown with ammonia. (2/5)

          Boletus lewisii

          Cap bright yellow, becoming brownish yellow; cap center dark brown with ammonia, cap margin pale bluish green with ammonia. (3/5)

          Boletus melleoluteus

          Cap eventually brownish yellow; cap reddish brown with ammonia. (4/5)

          Boletus ochraceoluteus

          Cap olive brown, becoming dingy yellow brown; cap amber with ammonia. (5/5)

          Boletus subdepauperatus

  • Mature cap larger, typically greater than 4-5 cm across. (2/2)

      > Found west of the Rocky Mountains, excluding Texas. (1/2)

        ° Cut flesh turning bluish slowly and erratically or only slightly. (1/2)

          ~ Cap nearly black, wrinkled when young, with a reddish margin; stem densely covered with reddish dots. (1/3)

          Boletus zelleri

          ~ Cap brown, becoming cracked in age; with reddish flesh showing in the cracks. (2/3)

          Boletus chrysenteron

          ~ Not as above. (3/3)

            Cap smooth, reddish brown to yellow brown; pore surface bruising blue; stem yellow with reddish brown stains; flesh blue with ammonia. (1/6)

            Boletus appendiculatus
            At MykoWeb

            Cap felty, red to reddish brown, cracking in age; pore surface bruising blue; stem yellow above, red or purplish red below; blued flesh bleached to yellow with ammonia. (2/6)

            Boletus dryophilus
            At MykoWeb

            Cap felty to smooth, olive to olive brown developing reddish shades; pore surface bruising blue; stem pinkish to reddish above, yellow below; flesh changes with ammonia not recorded. (3/6)

            Boletus smithii
            At MykoWeb

            Cap felty to smooth, olive to brownish, sometimes with red shades, sometimes becoming cracked; pore surface bruising blue or not bruising; stem yellow, without red shades; cap surface flashing green, then reddish brown with ammonia; flesh changes with ammonia not recorded. (4/6)

            Xerocomus ferrugineus

            Cap smooth or finely felty, yellow, often becoming cracked; pore surface bruising bluish, then brown; stem yellow; flesh changes with ammonia not recorded. (5/6)

            Boletus sphaerocephalus

            Cap felty, olive brown to yellowish brown, becoming cracked; pore surface bruising slightly bluish, then brown; stem yellow with reddish brown streaks, bruising brown or reddish brown; cap surface reddish brown with ammonia; felsh changes with ammonia not recorded. (6/6)

            Xerocomus subtomentosus

        ° Bluing of cut flesh more pronounced. (2/2)

          ~ Stem without red shades. (1/2)

            Cap dark olive gray, becoming brownish; under conifers. (1/2)

            Boletus coniferarum

            Cap sulphur yellow, fading to pale yellow or whitish; in sawdust or on stumps. (2/2)

            Boletus sphaerocephalus

          ~ Stem with red shades. (2/2)

            Stem yellow with red near the base; stem bruising dark green, then blackish, on handling; cap olive brown to blackish, becoming brownish, bruising greenish black. (1/3)

            Boletus rainisii

            Stem yellow at apex, red to purplish red overall; stem bruising blue, then grayish olive, on handling; cap buff to olive brown, bruising brown. (2/3)

            Boletus rubripes
            (At MykoWeb)

            Stem pinkish to reddish above, yellow toward base; stem not bruising on handling; cap olive to olive yellow, developing red shades, not bruising. (3/3)

            Boletus smithii
            (At MykoWeb)

      > Found east of the Rocky Mountains, including Texas. (2/2)



    Cite this page as:

    Kuo, M. (2003, June). Key to Boletus in North America (page five). Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/boletus_05.html


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