fairy ring A circle of dark-green grass (in a lawn or field) in which toadstools may be found. The circle is formed as a result of the radial growth of the fungus through the soil, away from the centre of the ring. Fairy rings are often formed by Marasmius oreades.

fairy ring A circle of dark-green grass (in a lawn or field) in which toadstools may be found. The circle is formed as a result of the radial growth of a fungus through the soil, away from the centre of the ring; as the fungal mycelium grows it deprives grass roots of nutrients, but as it dies and decomposes the release of nutrients stimulates the growth of the grass, producing the dark coloration. Fairy rings are often formed by Marasmius oreades.