Fairy Ring Mushroom

Family: 
Marasmiaceae
Description: 

Tan to reddish brown, knobbed cap; off-white gills. Grows in grassy areas, lawns, meadows, often in arcs or circles called fairy rings. May–September. Cap bell-shaped with inrolled margins, becoming convex and knobbed; pale tan to buff to reddish brown; texture dry, smooth, feltlike. Gills broad; spacing well-separated; off-white; gills attached or free. Stalk straight; cream to pale buff; texture dry, tough, feltlike. Spore print white. Spores magnified are elliptical, smooth, colorless.

Lookalikes: Certain poisonous Clitocybe and Inocybe species can be confused with the fairy ring mushroom. The sweating mushroom (Clitocybe dealbata), also poisonous, is gray-pink with gills running down the stalk. Poisonous Inocybe mushrooms usually have gray-brown gills.

Size: 
Cap width: ½–2 inches; stalk length: 1–3 inches; stalk width: 1⁄16 – ¼ inch.
Habitat and conservation: 
Grows in grassy areas, lawns, meadows, often in circles called fairy rings. Fairy rings can increase in size each year. The underground mycelium is continually spreading outward looking for nourishment, and each year when the mushrooms appear, the fairy ring is larger. In dry weather the fairy ring mushroom shrivels from lack of moisture, but after a rain the little mushrooms can revive, looking like they sprung up overnight.
Distribution in Missouri: 
Statewide.
Status: 
Considered edible—but with caution. Several species (some poisonous) can be confused with this mushroom, which could easily fit in the LBM (“little brown mushrooms”) category—one of many species that are confusingly similar. Be absolutely sure of your identifications before you consume wild mushrooms!
Life cycle: 
This species exists most of the time as a network of fungal cells (mycelium) in the soil, digesting and decomposing organic particles. It grows outward from a central point, in a rounded pattern. When it's ready to reproduce, the mycelium sends up mushrooms, which are aboveground reproductive structures. Because the most active parts of the mycelium are on the outer edge, mushrooms can appear in a circular "fairy ring." The mycelium of a mushroom can live for decades.
Human connections: 
While many mushrooms have been bestowed with poetic or fanciful names, the common name “fairy ring mushroom” may be misleading. Not all fairy rings are Marasmius oreades, and not all Marasmius oreades grow in rings. Use many resources to identify mushrooms, especially if you think it’s edible.
Ecosystem connections: 
This is one of the many fungus species that live on decaying organic materials. It and other such saprobic fungi play an incredibly important role in breaking down organic molecules and returning those nutrients to the soil.