Gyroporus cyanescens

First described from France in 1788, the species is found in Asia, Australia, Europe, and eastern North America, where it grows on the ground in coniferous and mixed forests.

The species was first described scientifically by French botanist Jean Baptiste François Pierre Bulliard in his 1788 Herbier de la France.

[11] The cap of G. cyanescens is initially convex, but flattens out in maturity, sometimes becoming shallowly depressed;[11] it reaches a diameter of 4–12 cm (1.6–4.7 in).

The stem tissue is hard and brittle; it is initially stuffed with a soft pith that develops cavities, or becomes entirely hollow in maturity.

It is initially covered in coarse hairs that tend to disappear in maturity to leave a relatively smooth surface.

[14] Although there are a few lookalike species with similar overall appearance, in the field, Gyroporus cyanescens is typically readily recognized by its characteristic straw-yellow color and nearly instantaneous dark blue bruising.

G. umbrinosquamosus, found along the Gulf Coast of the United States, is similar in appearance, but lacks the bluing reaction.

[11] If the fruit bodies are not uprooted and only the top of the cap is examined, G. cyanescens can be confused with young Russula fellea mushrooms.

Cooked mushrooms have a meaty texture, and mild nutty flavor that is enhanced if fried to crispness.

[19] The variety violaceotinctus is used in mushroom dyeing, and produces a light yellow, beige, gold, or brownish-orange color depending on the mordant used.

[21] Fruit bodies of Gyroporus cyanescens grow singly or scattered on the ground in deciduous and mixed forests.

Often found in association with birch and poplar, the fungus tends to prefer sandy soil,[10] and also frequents road banks and woodland edges.

[23] Infection results in necrosis of the mushroom tissue, and a yellow color caused by the formation of large amounts of pigmented aleurioconidia (single-celled conidia produced by extrusion from the conidiophores).

[13] The geographical distribution ranges from eastern Canada to Florida, and west to Minnesota,[10] although it has been occasionally reported from the Pacific Northwest,[19] and one collection has been made in the Sky Islands of southern Arizona.

[29] Gyrocyanin is biosynthesized from intermediates supplied by the shikimate pathway, a metabolic route used by fungi for the synthesis of aromatic amino acids.

Illustration from Bulliard's original description
When bruised, the variety violaceotinctus stains dark lilac (seen in left vertical line) that quickly changes color to blue.
The bluing reaction is caused by oxidation of gyrocyanin.