Summary:
{See also Yellow Russulas Table.} Clade Russula crown. The presence of this species in the Pacific Northwest should be confirmed and the host preference clarified. Russula claroflava is characterized by a yellow cap, a tendency to stain gray with age or injury, and a preference for birch habitat. Yellow Russulas that turn gray should be studied to see if they are R. claroflava or just pale versions of R. ''vinososordida''. While Russula flava Romell is thought to be a synonym of Russula claroflava, Russula flava var. pacifica Kauffman is probably not a synonym - Buyck(1) includes a type description of the variety.

Cap:
6-10cm across, fleshy, rounded; chrome yellow to pale lemon yellow; viscid drying shining, margin even becoming slightly grooved when old, peeling 1/2-2/3, (Woo), 3-10cm across, nearly spherical, cushion-shaped or convex, with margin inrolled when young, soon broadly convex to flat, finally flat-depressed; bright yellow to orange yellow, occasionally with rose tints, usually becoming gray to grayish black from margin inward when old; moist to viscid when wet, shiny, bald, sometimes radially streaked, often minutely rugulose [wrinkled], margin striate to tuberculate-striate, striations 0.1-1cm long, cuticle easily separable 1/2 to 3/4 of the way to the disc, (Bills), 6-8cm across, convex-flat; bright chrome-cadmium yellow (or paler more lemon-yellow); margin slightly striate-sulcate when old, (Lange), (3)4-12cm across, nearly round becoming convex to flat or slightly depressed; yellow to golden yellow; slightly viscid, soon dry, smooth, margin slightly striate when old, (Arora)

Flesh:
firm; white, becoming gray to black on bruising or when old, (Woo), firm when young, brittle when old, 0.2-0.6cm at midradius, very thin at margin; white, "cream-color" to pale gray, slowly discoloring gray when cut, in stem "sometimes slowly staining pale pinkish orange, but soon pale to dark gray where injured", (Bills), white, rather quickly becoming gray or even blackish when old, (Lange), white, slowly staining grayish when rubbed, (Arora), turns reddish then blackish when bruised or cut (Ammirati)

Gills:
"white, then yellow, eventually gray", (Woo), adnate or slightly notched, close to medium, with rare subgills, up to 0.9cm broad at midradius, rounded to subacute near margin, interveined, near stem often forked; white when young, soon pale yellow, often gray to dark gray when old, especially toward cap margin and gill edge; edge even, sometimes eroded when old, (Bills), almost white becoming pale custard-yellow, (Lange), "adnate to adnexed or free, close"; creamy becoming pale ocher, sometimes grayish-stained when old, (Arora)

Stem:
white then graying, (Woo), 2.5-7.5cm x 1-2.5cm at midpoint, equal or slightly flared at either top or base, spongy when young, remaining spongy or becoming hollow when old; white to pale gray, becoming dark gray or "cinereous" when old or when wounded; dry to moist, longitudinally rugulose or rivulose, (Bills), equal, white, often with a flush of yellowish, (Lange), 3-8cm x 1-2cm, more or less equal; white to pale yellow, aging or slowly bruising grayish; dry, smooth, (Arora), 4-10cm x 1-2cm, "soft but not fragile; white, turning gray with age or bruising (very slowly)", (Phillips)

Odor:
none, (Woo), not distinctive (Bills), mild, (Arora), pleasant (Phillips)

Taste:
mild or slightly peppery when young, (Woo), not distinctive (Bills), mild (Lange, Arora), mild to slightly peppery (Phillips)

Microscopic spores:
spores 8 x 6-6.5 microns, ornamentation Patterson-Woo type A-3, B-3, (Woo), spores 7.5-10 x 6-7.5 microns, obovate to broadly obovate, ornamentation amyloid, up to 1.2 microns high, consisting of isolated, conical to cylindric verrucae (warts) and many particles, sometimes aligned to form short chains, sometimes connected by a few faint lines, rarely forming a partial reticulum, suprahilar area depressed, ornamented with a large irregular amyloid patch, suprahilar appendix inamyloid, conspicuous; basidia 4-spored, 35-53 x 9-12.5 microns, clavate to broadly clavate; hymenial cystidia projecting 5-36 microns beyond basidia, arising from hymenium or subhymenium, 45-83 x 8-13 microns, clavate to cylindric with acuminate or mucronate apices, with refractive contents, (Bills), spores 8 x 6-6.5 microns, warts rather coarse, mostly isolated, (Lange), spores 8-9 x 6.5-7.5 microns, elliptic, warts 0.4-0.6 microns high, some catenulate, a few fine lines, (Hesler), spores 8.5-10 x 7.5-8 microns, broadly elliptic, amyloid warts and ridges, (Arora), (7.5)9-10 x (6)7.5-8 microns, warts up to 1 micron high, joined by numerous fine lines to form a fairly well-developed network, (Phillips)

Spore deposit:
yellow, Crawshay E-F, (Woo), yellowish orange, IIIa-b, (Bills), very pale creamy ocher (Lange), yellow-ocher (Arora), pale ocher, Crawshay F, (Phillips)

Notes:
It is included in the Pacific Northwest key of Woo(1). Bills & Miller examined collections from QC, AK, NJ, PA, TN, VA, WV, Finland, Netherlands, Sweden, and the United Kingdom (Scotland). Cripps reported it from MT, and Arora from NM. There is a collection from BC deposited at Pacific Forestry Centre by Paul Kroeger, and collections from BC at the University of British Columbia. The BC collections were from conifer areas with no mention of birch. A collection from MI is at the University of Washington. A. Parker''s photo in this program was taken in WA.

EDIBILITY

edible (Arora), good (Phillips)

Synonyms and Alternate Names:
Russula flava Romell