Gyroporus cyanescens

Bluing bolete

A straw-colored bolete with a coarse, matted-scaly cap whose every part turns deep blue almost instantly when cut or bruised. The brittle stem hollows early, and the spore print is pale yellow. It favors sandy soil along woodland edges, road banks and other disturbed ground. The bluing is caused by the pigment gyrocyanin, not the variegatic acid that stains other boletes.

Species profile

Edibility: Edible with caution

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Edible and rated choice by several guides; the blue color largely fades during cooking (Wikipedia). Confirm the straw-yellow, matted-scaly cap, instant deep bluing of all parts, hollow brittle stem and pale yellow spore print. Look-alikes include Suillus tomentosus (brownish pores that blue more slowly), young Russula fellea (check the stem base) and Caloboletus marshii (light bluing, not at the stem base). Eat only well-cooked, confidently identified specimens.

Habitat

Mycorrhizal, probably mainly with oaks and other hardwoods, sometimes under conifers; birch and poplar associations are also reported. Singly or scattered on sandy soil at woods' edges, road banks and other grassy or disturbed ground. Summer and fall.

Distribution

Described from France; widely distributed but fairly rare in Europe, and also recorded from Asia and Australia. In North America it occurs widely east of the Great Plains, from eastern Canada to Florida and west to Minnesota, with occasional reports from the Pacific Northwest and one from southern Arizona.

Characteristics

Cap: 4-12 cm, convex becoming nearly flat; dry, coarsely roughened or matted-scaly; straw-colored, bruising blue. Pore surface: white to yellowish, bruising blue immediately; 1-3 pores per mm, tubes to 18 mm deep. Stem: 4-12 cm long, 1-3 cm thick, brittle, hollowing early, not reticulate, bruising blue. Flesh: white to pale yellow, brittle, promptly bluing. Odor and taste: not distinctive. Spore print: pale yellow. Spores: mostly 8-11 x 4-5 µm, smooth, ellipsoid (MushroomExpert).