Marasmiellus luxurians

🔎 Identification

Marasmiellus luxurians, previously known as Gymnopus luxurians or Luxury Caps, is an attractive mushroom notable for forming large, conspicuous clusters in urban, suburban, and occasionally wooded environments.

🍄 Cap: The caps range from 1.18 to 4.33 inches (3 to 11 cm) across, beginning convex with a curled-in margin and maturing into broadly convex or flattened shapes. When young, caps are dark reddish-brown, fading gracefully to pinkish tan, often becoming streaked or slightly lined with age.

🌿 Gills: The gills are narrow, close, and white initially, becoming pale pinkish-tan over time, frequently with short-gills interspersed. The stem measures 1.57 to 2.76 inches (4 to 7 cm) long and 0.16 to 0.59 inches (0.4 to 1.5 cm) thick, tough, often twisted, and longitudinally ridged, white above and brownish below, darkening as it matures. Notably, the base often features cottony white mycelium and distinctive white rhizomorphs.

🍃 Habitat & Ecology: This mushroom is saprobic, thriving in woodchips, lawns (likely fruiting from buried dead roots), or occasionally directly from logs and stumps. It frequently emerges after watering in summer when few other mushrooms appear, continuing into fall. Marasmiellus luxurians is widely distributed and relatively common east of the Great Plains in North America, occasionally appearing in western regions, and can also be found across all continents except Africa and Australia.

🌎 Distribution: You’ll often encounter this fungus in urban flower beds, suburban lawns around tree roots, and occasionally woodland settings. Particularly common where moisture is abundant, it thrives in loose to dense clusters, making it a striking sight in gardens or parks.

👃 Odor & Taste: The mushroom possesses no distinctive odor, occasionally slightly fragrant, and its taste ranges from indistinct to slightly bitter.

🔬 Microscopic Features: Its spores measure 7–11 x 3–4.5 µm, appearing elongated almond-shaped (long-amygdaliform), smooth, and hyaline in potassium hydroxide (KOH). Cheilocystidia are present, typically cylindrical to irregularly clavate, measuring 20–40 x 3–7 µm. Pleurocystidia are absent. Young caps have heavily encrusted hyphae, whereas older, faded caps possess smooth, transparent hyphae.

🧪 Chemical Reactions: Applying potassium hydroxide (KOH) to the cap surface yields a gray to olive-gray reaction, or a weak pale gray to negative reaction in older specimens.

👀 Look-Alikes

Similar species include Gymnopus erythropus and Gymnopus peronatus, but Marasmiellus luxurians stands apart by its distinctive clustered growth, the significant color change from reddish-brown to pinkish-tan caps, twisted stems, and habitat preferences.

📜 Synonyms

• Collybia luxurians Peck (1897), Bulletin of the Torrey botanical Club, 24(3), p. 141

• Collybidium luxurians (Peck) Murrill (1911), Mycologia, 3(4), p. 169

• Gymnopus luxurians (Peck) Murrill (1916), North American flora, 9(5), p. 362

• Collybia compressiceps H.E. Bigelow (1976), Rhodora, 78, p. 124

• Collybia crassipes ss. Noordeloos (1995), Flora Agaricina Neerlandica, 3, p. 114

Photo sources:

Photo 1 - Author: Denis Zabin (CC BY 4.0)

Photo 2 - Author: Frederick Nunley (CC BY 4.0)

Photo 3 - Author: Frederick Nunley (CC BY 4.0)

Photo 4 - Author: Brand R (CC BY 4.0)