Cap: 25-80 mm, broadly conical at first, often lobed, later expanded and flattened with umbo (raised area in centre) and splitting margin, young fruitbodies slightly greasy, sometimes viscid when moist, but soon dry, radially fibrillose, with yellow flesh visible between fibres, reddish brown or olive-brown to dark blackish- greyish- brown. Gills: free to adnexed (rounded towards stem), lemon-yellow with a pale yellow margin, sometimes turning deeper orange with age. Stem: 35-90 x 3-12mm, terete (round cross section), longitudinally fibrillose, lemon-yellow to egg-yellow, later with orange or brownish fibres often forming a darker band in the middle, very brittle and easily splitting. Flesh: yellowish. Spores: (8-)9-12(-14.5) x (4.5-)5-7(-10) μm Q = 1.4-2.2, average 1.5-1.9, ellipsoid, oblong or occasionally broadly ellipsoid, sometimes constricted or bean shaped. Basidia: 35-64 x 8-12 μm, predominantly 4-spored, but often 2-spored. Gill trama: regular, with elements up to more than 1000 μm long, ends sometimes projecting from gill-edge as pseudocystidia. Pileipellis: a cutis, in young fruitbodies with a thin, slightly gelatinised layer overlaying broader hyphae (3-6 μm broad) with yellowish-brownish intracellular pigment. Stipitipellis: a cutis of 2-5 μm wide hyphae with many erect, filiform (thread like) terminal elements.
Description adapted from D. Boertmann, The genus Hygrocybe (2010).