Atkinson’s Fungi

Cortinarius is the largest genus of gilled mushrooms. There are estimated to be over 1,000 species worldwide.

Cortinarius atkinsonianus, commonly known as Atkinson’s Fungi, is a common and widespread mushroom in eastern North America. It is found on the ground either scattered or growing close together (gregarious) but not in clusters. It is sometimes found in rings or arcs. It obtains its nutrients from the rootlets of living trees (mycorrhizal). It appears in the fall under or near hardwoods in deciduous and mixed forests and woodlands.

The cap is 2″ to 6″in diameter. It is slimy when it first emerges from the ground. When young it is olive-yellow to yellowish and convex, and the margin is rolled inward. The surface is smooth when dry, sticky or slimy when moist. Later it may be dry but with dirt and debris stuck to the cap. As it ages the cap becomes broadly convex or flat and darkens to deep reddish-brown from the center outwards, with the margin remaining olive-yellow.

The stalk 1½″ to 4¾″ tall and ⅝″ to 1¼″ in diameter at the top. When young, it has a conspicuous, abrupt, rimmed, 1¼″ to 2¾″ wide bulb at the base. As the stalk lengthens, the bulb becomes less abrupt. The stalk is solid and dry, not slimy or sticky. The color is variable, with olive-yellow or pale lavender at the top or throughout its length.

The gills are closely spaced and are narrowly to broadly attached to the stalk. They do not run down the stalk. They are greenish-yellow at first, become pale lavender with yellow edges for a short time, ultimately fading to cinnamon-brown. When young, the gills are protected with a partial veil that is cobwebby or silky in texture (cortina). The cortina is greenish-yellow at first, becoming rusty-brown as it is covered with spores. When it collapses to allow the dispersal of spores, it leaves hairs on the stalk that trap the spores.

The flesh is thick, firm, and whitish to pale yellow with lavender or violet areas. It stains lavender or violet when bruised. The edibility is unknown. However, many Cortinarius mushrooms are poisonous. Due to the difficulty of identifying them to the species level, it is recommended that Cortinarius mushrooms are not eaten.

The spore print is rusty-brown.

Deciduous forests and woodlands

Fall

Sources

7, 26, 29, 30, 77.

Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu, 6/16/2025).

Habitat

Fairy ring

Cluster

Cluster

Cluster

Cluster

Cap

Fruiting body

Stalk

Stalk

Gills

Flesh