Myths and superstitions about the origins of fairy rings have persisted for centuries. In Holland, the rings mark places where the devil churns his butter. In France, entrance into a fairy ring might mean an encounter with a giant toad. In England, building a house on land scattered with fairy rings was considered a good omen.
But despite their charming mythology, they will litter your lawn. Many soil-inhabiting fungi can cause fairy rings. Although the rings vary in size and shape, they are usually distinct circles or semi-circles of turf grass that are darker green and faster growing than the surrounding grass. These stimulated grass bands may range from 4 to 12 inches wide, with a diameter of 3 to 200 feet. Characteristically, mushrooms or toadstools can appear in the rings in later summer during periods of high soil moisture.
Fairy rings are classified in three main types. Some fairy rings are detected only by the presence of the ring of mushrooms or puffballs. Another type of ring exists where the grass is stimulated by the release of methane gas created by the decomposition of organic matter within the soil. The most devastating type of fairy rings kill the turf, leaving a circle of expose soil with stimulated grass sprouting on the inside and outside margins.