The circular growth pattern of mushrooms in grassland or woodland is commonly called a fairy ring.
A fairy ring is a naturally occurring ring or arc of mushrooms, produced as fungal mycelium expands outward through soil. The older central region may become depleted of nutrients, leaving a living outer edge where mushrooms appear. The underground mycelium can therefore form a ring even when the fruiting bodies are visible only seasonally.
The pattern may also alter vegetation. Some fungi create a dark-green band by releasing nutrients or growth-affecting compounds, while others produce a zone of dead or weakened grass. Fairy rings occur in forests, meadows, and rangelands, and roughly 60 mushroom species are known to grow in this pattern.
The name reflects European folklore, in which fairies, elves, or witches were said to dance in circles. Fairy ring is not the same as the unrelated “fairy circle” vegetation gaps found in arid regions such as Namibia.