Marasmius oreades in a fairy ring.
Fairy rings are naturally occurring circles or arcs formed by mushrooms. Depending on culture, they are thought to bring either death or growth.
Fungi, living in threads underground, produce mushrooms when they are ready to reproduce. The fairy ring is formed when the mushrooms pop up at the edges of the fungus, which is growing underground. They can be found in forests, grasslands or even your front yard.
Depending on the species of fungus growing, the fairy ring is sometimes surrounded by dead grass, or is proceeded—or followed—by rapid growth of the grass above it. This may explain why fairy rings can be associated with either death or growth.
Mushrooms on high legs stand nearby in a circle.
There are just over 60 species of fungi that grow into fairy rings. The oldest fairy rings are thought to be hundreds of years old. One fairy ring in France spans over 2,000 feet in diameter and is thought to be over 700 years old.
Scientists based in Italy released a new study this week on fairy rings and how they alter the ecosystems they appear in. The study focused on Agaricus arvensis, which forms fairy rings in Mediterranean grasslands with many plant species.
In the mountains of central Italy, the scientists focused on the outside edges encompassed by the fairy ring. They picked fairy rings that were about 30 to 40 feet in diameter. The fairy rings in this region expand about two feet each year. The scientists found that as the fairy rings spread, they decreased the diversity of plant and microbial species that were found before.
The A. arvensis fairy rings made it easier for short-lived, fast-growing plants to take over an area of the grassland that used to have perennial (plants that bloom and persist many years) plants.
The scientists believe that these fairy ring fungi could be acting as ecosystem engineers in these Mediterranean grasslands, altering the species that are found by promoting the growth of certain species over others.
Ancient lore is right: fairy rings bring both life and death.