When do we see Fairy Rings?

A Fairy ring is a circular pattern that is produced by fungi growing in grassland. As the fungus grows out from a central point it forms a circle, and at the edges of this circle the grass changes in appearance.. Meanwhile the original fungus dies of, so that is left is the expanding ring of the fungus growing beneath the surface. Sometimes a ring of mushrooms also appears. These fairy rings keep growing for many years, perhaps even for centuries. They can reach a very large size unless disturbed, for example when the land is ploughed.