Major Groups > Boletes > Leccinum > Leccinum rugosiceps


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Leccinum rugosiceps (Peck) Singer, 1945

= Boletus rugosiceps Peck, 1905
? = Boletus rimosellus Peck, 1889

by Michael Kuo


Leccinum rugosiceps is a well documented, easily recognized species occurring with oaks in eastern and southeastern North America (it is also well documented in Central and South America). It can be recognized in the field by its distribution and ecology; its hard, staining flesh; its yellowish (but not bright yellow) pore surface; its brown to reddish brown (but not black) scabers; and its yellow to brown cap. Under the microscope it features a pileipellis disposed as a trichoderm with slightly swollen penultimate and antepenultimate elements, and clavate to fusoid caulocystidia that are yellowish in KOH.

Technical Description:

Ecology: Mycorrhizal with oaks; appearing alone or gregariously in (June,) July, August, and September (October). Analysis of 70 collection records from online herbaria (see Figure 1) reveals only one record in which oak is actually excluded by the collector's brief notes. In my experience Leccinum rugosiceps is frequently found in areas where the substrate has been disturbed (usually years ago) by human activity: pathsides, picnic areas, clearings that have been followed by old-field regrowth, and so on. Several collectors I know have noticed a similar tendency in their collections.

Distribution: Apparently widely distributed east of the Great Plains and especially common in the southeastern United States. Among the 70 collections found in online herbaria, only one was found outside this range, in California; I have excluded this collection on the assumption that it probably represents a misidentification. Halling & Mueller (2003) have described Leccinum rugosiceps from Costa Rica, and records in NY document the species in Colombia.

Macromorphology: Pileus 3-15 cm; convex becoming broadly convex or plane; surface dry or slightly tacky, very finely tomentose or glabrous; frequently pitted or rugulose in youth and/or areolate at maturity; color variable, but frequently mustard yellow to orangish yellow young, becoming brownish yellow or brownish before fading to tan--or medium brown young, fading to yellowish brown or tan; with a tiny (1 mm) sterile margin but without substantial overhanging flaps. Context quite firm (nearly brittle when young); whitish or pale yellowish; changing to pinkish or reddish when sliced and exposed to air, then grayish to blackish over the course of 20-60 minutes (Figure 3). Tubes to 2 cm long; yellowish to greenish yellow; pore surface dull yellow to yellowish, becoming olive yellow or brownish, not bruising or bruising brownish, depressed at the stipe; 1-2 pores per mm. Stipe 4-15 cm long; 14-30 mm wide; often subclavate when young but at maturity more or less equal, or tapering to apex and/or base; yellowish or whitish (sometimes with reddish areas, especially in wet weather); finely pruinose or subreticulate apically; scabrous for about the bottom two-thirds with yellowish, medium brown, cinnamon brown, or grayish brown scabers; basal mycelium whitish to yellowish. Odor and taste not distinctive. Exsiccata with a dark reddish brown pileus surface, a dull grayish olive to dirty ochraceous pore surface, and a brownish ochraceous stipe surface adorned with concolorous or brownish scabers. Spore print brownish to olive brown.

Chemical reactions (Figure 4): KOH red on pileus surface; golden yellow to rusty or orangish on context. Ammonia reddish or negative on pileus surface; yellowish to negative on context. Iron salts grayish on pileus surface, greenish gray to olive on context.

Micromorphology: Basidiospores subfusoid; inamyloid; yellowish in KOH; smooth; (9.5-) 12-21 x (3-) 4-6 µ. Basidia clavate; four-sterigmate; up to 40 x 12 µ. Hymenial cystidia (Figure 5) fusoid-ventricose with a long neck; up to 48 x 13 µ; hyaline to yellowish in KOH; scattered to numerous. Pileipellis (Figure 5) a trichoderm of chained elements, the penultimate and/or antepenultimate (occasionally the terminal) element often swollen up to 33 µ wide; hyaline to yellowish or brownish in KOH. Caulocystidia (Figure 5) in bundles with caulobasidia; variously shaped but mostly fusoid-ventricose with a long, twisted neck; also mucronate, clavate, or irregular; up to 70 x 20 µ or longer; hyaline to yellowish brown in KOH.

Molecular Data: Two partial sequences have been deposited in GenBank: DQ407250 (partial ITS1-complete 5.8S-partial ITS2, deposited by Y. Zhao, citing a Y. Zhao collection from China in an uncited herbarium), apparently not publicly aligned; and AY612813 (partial 28S, deposited by T. Y. James and collaborators with a voucher of "TH6967" in an uncited herbarium), aligned by Binder & Hibbett (2004) and by den Bakker & Noordeloos (2005). The Binder & Hibbett and den Bakker & Noordeloos alignments are similar, though not identical, placing AY612813 in a clade with oak- and hornbeam-associated taxa; in the den Bakker & Noordeloos alignment AY612813 is sister to a clade containing Leccinum subglabripes, Leccinum longicurvipes, Leccinum crocipodium, and other taxa; in the Binder & Hibbett alignment it is sister to a specimen identified as Leccinum albellum.


Leccinum rugosiceps is a well documented and thoroughly described taxon.


Leccinum rugosiceps

Leccinum rugosiceps

Leccinum rugosiceps

Leccinum rugosiceps
Figure 1

Leccinum rugosiceps
Figure 2

Leccinum rugosiceps
Figure 3

Leccinum rugosiceps
Figure 4

Leccinum rugosiceps
Figure 5

References and Material Studied:

Collections Examined: ILLINOIS: Kuo 08309704 (Douglas County); Kuo 08240208 (McLean County); Kuo 07220318 (Vermillion County); Kuo 07170400 & 08010400 (Coles County).

Online Herbarium Records Examined: NY< 34; MICH: 15; OSU: 0; TENN: 0; BPI: 21.

Field Guides and Online Treatments: Smith, Smith & Weber, 1981; Weber & Smith, 1985; Phillips, 1991/2005; Metzler & Metzler, 1992; Bessette, Roody & Bessette, 2000; Miller & Miller, 2006; Halling & Mueller, 2007; Phillips, 2007; Kuo, 2007.

Technical References: Singer, 1947; Smith, Thiers & Watling, 1967; Snell & Dick, 1970; Smith & Thiers, 1971; Both, 1993; Halling & Mueller, 2003; Binder & Hibbett, 2004; den Bakker & Noordeloos, 2005; Ortiz-Santana et al., 2007. Full citations for these works can be found here.

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Kuo, M. (2007, April). Leccinum rugosiceps. Retrieved from the MushroomExpert.Com Web site:

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