Leccinum holopus: The Ultimate Mushroom Guide
About The Leccinum holopus Mushroom
Leccinum holopus is a species of bolete fungus in the family Boletaceae found in northern Asia, Europe, and northeastern North America. It associates with birch trees and is typically found in boggy or swampy areas, often growing among sphagnum moss. It has pure white fruit bodies—the caps sometimes become flushed with buff or brownish tints. The whitish surface of the stipe is covered with small, stiff, projecting scales (scabers) that become tan or darker in age.
Some varieties of Leccinum holopus have been described that vary in cap color or staining reaction, but DNA evidence suggests that most are the same taxon. Although the fruitbodies are edible, opinions vary as to their culinary desirability.
Other names: White Birch Bolete, White Bog Bolete, Ghost Bolete.
Leccinum holopus Identification
Mycorrhizal with birches (in North America with paper birch, in Europe and Asia with European white birch); appearing alone or gregariously; summer and fall; widely distributed in northern North America from roughly the 43rd parallel northward (but also found underwater birch in the Rocky Mountains); also known from northern Europe.
2–7 cm; convex, becoming broadly convex; sticky or dry (sometimes becoming more sticky with age); bald; pale brownish to nearly white; discoloring and aging brownish or, in wet conditions, pinkish or bluish; margin with a very tiny sterile overhang.
Creamy white, bruising a little brownish; 2–4 circular pores per mm; tubes to 12 mm deep; by maturity depressed at the stem.
4–15 cm long; 1–2 cm thick; equal, or with a tapering apex; finely scabrous with whitish to brownish, brown, or nearly black scabers; ground color whitish; sometimes staining blue near the base.
White; not staining on exposure, or staining slowly pinkish (allow up to half an hour); sometimes bluing a little in the stem base.
Odor and Taste
Ammonia pink on cap surface; pinkish on flesh. KOH red or negative on cap surface; negative on flesh. Iron salts negative on cap surface; bluish or negative on flesh.
Spores 14–19 x 4–6.5 µm; fusiform; smooth; hyaline to yellowish in KOH. Basidia to about 30 x 10 µm; clavate; 4-sterigmate. Hymenial cystidia 30–50 x 7.5–12.5 µm; variously shaped but primarily lageniform; smooth; thin-walled; hyaline in KOH. Pileipellis a cutis or collapsing trichoderm of elements 4–7.5 µm wide, smooth, thin-walled, hyaline or golden (especially the terminal cells) in KOH; terminal elements cylindric with rounded or subacute apices. Caulocystidia in bundles with caulobasidia; variously shaped but often lageniform with a long neck; up to 75 x 20 µm; hyaline to yellowish in KOH.
Leccinum holopus Look-Alikes
Also occurs under birch, usually has a brown cap but is occasionally yellowish-brown; its stem flesh does not usually display a marked color change when it is cut, although occasionally it turns pinkish-red.
Very similar, but is associated with oaks rather than birches.
Leccinum holopus Taxonomy & Etymology
This mushroom was described in 1844 by German mycologists Friedrich Wilhelm Gottfried Theophil Rostkovius (1770 - 1848), who gave it the binomial scientific name Boletus holopus. The currently accepted scientific name Leccinum holopus dates from a 1960 paper by British mycologist Roy Watling, published in the Transactions of the British Mycological Society.
Synonyms of Leccinum holopus include Boletus holopus Rostk., Leccinum holopus var. americanum A.H. Sm. & Thiers, Krombholziella holopus (Rostk.) Šutara, Leccinum nucatum Lannoy & Estadès, and Leccinum olivaceosum Lannoy & Estadès.
Leccinum, the generic name, is derived from an old Italian word meaning fungus. The specific epithet holopus comprises the prefix holo- meaning whole or entire, and the suffix -pus meaning foot, stalk (stem) or base.
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