Sometimes after a wet spell, mushrooms pop up in a perfectly round circle in a lawn or meadow. Old European folklore said fairies had been dancing there overnight. The real explanation is even cooler. The mushrooms are coming from one single fungus growing outward underground in every direction at the same speed.
The fungus starts from a single spore in the middle. Its mycelium spreads outward in all directions, slowly using up nutrients in the soil as it goes. Each year only the outermost edge has fresh territory, so that’s where it fruits - sending up mushrooms in a perfect ring.
Some fairy rings are hundreds of years old. The biggest known ring, near Belfort in France, is over half a kilometre across and has been growing for an estimated 700 years. Even better, the soil inside a fairy ring often has lush, dark-green grass because the fungus releases nitrogen as it digests organic matter.
