Gregarious on the ground in various habitats; mainly under coniferous trees but also in mixed woods. Autumn to late autumn. Widespread and often common, but rare in parts of western Europe. Widely distributed and common in southern Norway, more rare in the north. Recorded north to Troms.

Pileus 20-50 mm across, parabolical, conical to broadly conical, becoming plane with age, with or without umbo, glabrous, sulcate, translucent-striate, with age becoming stained with brown spots, at first dark brown with white margin, becoming whitish to beige or uniformly grey or grey-brown, often with brown centre and somewhat paler margin. Lamellae 23-27 reaching the stipe, ascending, narrowly adnate, decurrent with a short tooth, dorsally intervenose with age, white or very pale grey, sometimes getting a faint pink flush with age, becoming stained with brown spots with age, the edge white to concolorous. Stipe 30-70 x 2-5 mm, hollow, terete or somewhat compressed and occasionally fissured, straight to curved, very fragile, white-floccose or covered with a silvery hue, at first dark greyish brown, then dark brown in the whole length or whitish to silvery grey at the apex, darker below, gradually turning dark grey to dark vinaceous brown, the base densely covered with white fibrils. Odour indistinctive or more or less pronounced raphanoid. Taste mild to somewhat bitter.

Basidia 28-32 x 7-8.5 µm, clavate, 4-spored, with sterigmata up to 7 µm long. Spores 8.5-12.2 x 4-5(-6) µm, Q1.9-2.7; Qav~2.3, elongated pip-shaped to almost cylindrical, smooth, amyloid. Cheilocystidia 44-78 x 6-20 x 0-5 µm, forming a sterile band, fusiform, clavate, subcylindrical, apically mucronate or narrowed into a simple neck or covered with a few very coarse, simple to somewhat branched excrescences, more rarely obtusely rounded. Pleurocystidia similar, if present. Lamellar trama dextrinoid. Hyphae of the pileipellis 2-9 µm wide, smooth to very scarsely covered with warts to simple excrescences up to 10 x 3 µm, terminal cells near the margin of the pileus up to 12 µm wide, clavate, smooth to diverticulate. Hyphae of the cortical layer of the stipe 2-5 µm wide, smooth to covered with coarse, simple to somewhat branched excrescences 2-10 x 1.5-2 µm, terminal cells 5-10 µm wide, coarsely diverticulate. Clamp connections present in all tissues.

Microphotos of cheilocystidia, pileipellis, spores, stipitipellis and caulocystidia

Mycena zephirus is a rather easily identified member of sect. Fragilipedes. The pale pileus with brown spots is a good character, and so is the silvery white-floccose stipe. Young specimens often appear without brown spots but are usually still easy to identify. They can be determined on account of the large size, dark brown pileus, large number of lamellae, white-floccose, very fragile stipe, smooth hyphae of the pileipellis, smooth cheilocystidia with one or few coarse excrescences, and fairly large, elongated spores.