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Species Information
Summary: Features include 1) dingy brownish bald cap, 2) white flesh that may turn brownish, or in stem base blue, 3) whitish pores that darken but do not turn blue, 4) whitish stem with dark brown to black scabers, and 5) growth under birch. Leccinum scabrum was probably introduced with planted birches but does occur with natural birches, for example in northern ID and WA, (Trudell).
L. scabrum has been found in eastern Canada south to GA, west to AK and CA, (Bessette), BC (Bandoni), WA and OR, (numerous observers), ID (A. Parker, pers. comm.), MI (Smith), NS (Grund), and also Europe (Breitenbach).
Cap: 4-10cm, obtuse to broadly convex; "grayish brown to yellow-brown when young", often developing olive tones when old; moist or dry, bald, (Bessette), 4-10cm, cushion-shaped to broadly convex; "grayish brown to dull yellow-brown" and often flushed olivaceous when old; "moist to dry or when wet fairly viscid", "glabrous and often with depressions in age"; margin scarcely projecting beyond tubes, (Smith), "dull brown to grayish brown to dingy yellow-brown or tan" (but often developing olive tints when old), lacking marginal flaps of tissue, (Arora), dry to viscid, may be somewhat tomentose, may crack when old, (Trudell)
Flesh: "white, not changing or sometimes slowly brownish when exposed", in stem white, unchanging or slowly staining pinkish near stem surface or turning blue near base, (Bessette), white, ''when cut not staining or slowly becoming slightly brownish (near "pinkish buff")'', in stem white, slowly staining pinkish buff in cortex when cut, "also developing both blue and red stains in restricted areas lower down if wet", (Smith: it is not totally clear from the description whether the blue and red stains are in the stem flesh or on the surface), dull whitish or pallid becoming dingy brownish when old, not turning blue when bruised but sometimes staining slightly yellowish or ocher, (Arora)
Pores: 2-3 per mm, round to irregular; whitish at first, becoming grayish to brownish when old, "not staining when bruised or slowly staining yellowish"; tube layer 0.7-1.6cm thick, (Bessette), small; pallid then colored as tubes and either not staining when bruised or staining yellow; tubes 0.8-1.5cm thick, deeply depressed around stem, "pallid, slowly becoming wood-brown as spores mature", (Smith), "cream to pale tan or olive-buff" (Trudell)
Stem: 7-14cm x 0.7-1.6cm, widening downward, solid; whitish, with dark brown to blackish scabers, sometimes with bluish green stains near base; dry, (Bessette), 7-12(15)cm x 0.7-1.2(1.6)cm, evenly widening downward, solid; pallid ground color with scabers dark brown to blackish ("dark brown to blackish punctate to nearly reticulate or squamulose decorations"), (Smith), club-shaped, often long in relation to the diameter of the cap, (Trudell)
Chemical Reactions: cap cuticle stains reddish brown with application of KOH, bluish slate with FeSO4; flesh reddish-brown with application of KOH, bluish slate with FeSO4, (Bessette)
Odor: mild (Bessette, Smith)
Taste: mild (Bessette, Smith)
Microscopic: spores 15-19 x 5-7 microns, subfusiform [somewhat spindle-shaped], smooth, pale tawny; cap cuticle end cells "typically uniform and parallel, not inflated and clavate to subglobose"; caulocystidia "mostly clavate with dull ochraceous content in KOH", (Bessette), spores 15-19 x 5-7 microns, subfusiform, smooth, pale tawny in Melzer''s reagent, when revived in KOH pale tawny singly and darker in groups, wall thickened to about 0.5 microns revived in KOH; basidia 4-spored, 11-13 microns wide, colorless in KOH and yellowish in Melzer''s reagent; pleurocystidia none; cap cuticle "a tangled layer of floccose hyphae 6-12(15) microns wide, above a subgelatinous subcutis, their content smoky ochraceous in KOH and with a grayer shadow in Melzer''s but content remaining granular to homogeneous", wall at first enveloped in outer gelatinous matrix that dissolves slowly in KOH, at times a few short slightly inflated cells seen; caulocystidia mostly clavate, 32-46 x 9-17 microns, with smoky ochraceous content in KOH, some clavate-mucronate, and a few varying to fusoid-ventricose; clamp connections absent, (Smith)
Spore Deposit: brown (Bessette), olive-buff (Miller)
Habitat / Range
single, scattered or in groups on ground under hardwoods, especially birch, (Bessette), under birch (Smith), summer and fall (Miller), common in urban and suburban settings and less so in natural habitats, (Trudell)
Similar Species
Leccinum brunneum of California and probably Idaho grows with aspen, and has a dark brown cap that fades to paler brown when old and does not stain blue, whitish stem with whitish scabers that darken when old, and white flesh that stains fuscous without an intervening reddish stage, (Bessette). Leccinum alaskanum in Alaska grows with birch but has a dark brown mottled cap (Bessette). See also SIMILAR section of Leccinum rotundifoliae.
