Summary:
Features include 1) a smooth, slimy or viscid, yellow-orange to reddish brown or dark brown cap, 2) a stem that is dark brown and velvety at maturity, at least in its lower part, 3) the absence of a veil, 4) clustered growth on dead hardwoods, and 5 a white spore deposit. Fruiting bodies can apparently survive freezing and continue to produce spores after thawing. Flammulina velutipes often grows through winter. It is cultivated as enokitake which looks different.

Cap:
1-5(7)cm across, convex to flat or broadly umbonate, margin at first incurved; reddish brown to yellow-brown, yellow-orange, orange-brown, or tawny, "margin often paler (yellower)", fading in dry weather; "smooth, slimy or viscid when moist", (Arora), 1.7-5cm across, convex then flat, margin staying inrolled, often wavy and irregular, occasionally frayed; "brownish yellow to dark warm brown", "color may vary considerably from collection to collection", generally bright yellowish toward the margin and darker, reddish brown on the disc, intergrading uniformly, "spotting or staining dark brown"; "viscid and shining, dull quickly in drying", bald, cap skin peeling easily from cap, translucent-striate half to three-quarters of radius, (Lennox)

Flesh:
thin; white or yellowish, (Arora), thin to moderately thick, firm, almost tough; yellow to dark brown just below the cap surface, in stem with a dark brown outer rind, yellow within, (Lennox)

Gills:
"adnate to adnexed or notched", close; white to pale yellow, (Arora), emarginate to sinuate, subdistant to close, up to 40 gills reaching stem, broad, 0.9-0.35cm broad, sharp pointed at the margin, blunt toward the stem, ventricose; off white to yellow, edges colored as faces; edges even, (Lennox)

Stem:
2-11cm x 0.3-0.5(1.2)cm, equal or thicker in lower part, "slender, tough, often curved, sometimes slightly off-center", "smooth and pallid to yellowish to orange-brown when young", but developing a rusty brown to blackish brown velvety pubescence from base upward as it matures, (Arora), 2.5-10.5cm x 0.2-0.5(1.2)cm, equal and confluent at base and somewhat expanded there, round in cross-section or more often compressed and furrowed, hollow; yellow at top, "soon a dark yellowish brown and then a dark fulvous brown", stem somewhat spotted with a darker brown tone; dull, densely covered with short fulvous hairs the entire length, brown rhizomorphs at base, (Lennox)

Veil:
ring none

Odor:
pleasant (Phillips), none (Lennox)

Taste:
pleasant (Phillips), none (Lennox)

Microscopic spores:
spores 6.5-9 x 3-5 microns, elliptic to pip-shaped, smooth, inamyloid, cystidia on gills, (Arora), microscopically cap has ixotrichoderm of filamentous to branched and thorny ixohyphidia, as well as pileocystidia [illustrated], (Redhead(37)), spores frequently in two sizes, 6.5-7.5 x 3-4 microns and 7.5-9 x 3.5-4 microns, cylindric-elliptic to almost pip-shaped, "smooth, generally with a somewhat thickened wall", inamyloid; basidia 2-spored or 4-spored mixed, or entirely 4-spored, and then lacking the longer cylindric to pip-shaped spores, 16-24 x 4-6 microns, "very elongate, shape variable, tapering gradually downward or abruptly enlarged in upper half", inamyloid, thin-walled; pleurocystidia not differentiated; cheilocystidia "abundance very variable, sometimes so numerous as to exclude basidioles on gill edge, occasionally so rare as to be absent from any one crush mount", 26-57 x 9-14 microns, "ventricose, quite large in diameter and generally widest in the lower half, often pedicellate, tapering gradually upward to an obtuse broad apex, thin-walled, arising rather shallowly from the subhymenium", "frequently mixed with filamentous outgrowths from the trama, the presence and abundance of the latter being variable as well, generally equal, with a straight outline, sometimes contorted", (Lennox)

Spore deposit:
white (Arora), pale yellow (Lennox), cream-white (Buczacki)

Notes:
Flammulina velutipes has been found (as differentiated from F. populicola) at least in BC, WA, and OR, (Lorelei Norvell, pers. comm.). Desjardin(6) also lists it from CA separately from F. populicola.

EDIBILITY

yes, but remove sticky skin before cooking, (Arora), anaphylactic reaction has been reported in Otsuji et al. 2015 (Benjamin), Flammulina velutipes has a toxic hemolytic protein dubbed flammutoxin which is not heat stable, and cultured Flammulina velutipes (enoki) can be contaminated by bacteria like Listeria, (Kroeger(8))

Synonyms and Alternate Names:
Collybia velutipes (Curtis ex Fr.) P. Kumm.