Fairy Ring

For centuries, the sudden and rapid eruption of circles of mushrooms from the soil led people to believe that dark or terrible forces were at work. Lightning strikes, meteorites, shooting stars, earthly vapours, and witches have all been proposed as agents of their origin.

In France fairy rings were called sorcerers' rings and in Austria, witches' rings. A Tyrolean legend claims that the rings were burned into the ground by the fiery tail of a dragon. In Holland they were said to be the marks where the Devil rested his milk churn. In Europe, the belief that fungi were the work of evil spirits or witches persisted well into the 19th century.

In England, as their name suggests, they were places where fairies come to dance. The mushrooms around the perimeter were seats where the sprites could rest after their exertions. People in rural England claimed to have seen fairies dancing at fairy rings as recently as the start of the twentieth century.

One common theme in all these traditions is the belief that dire consequences await anyone foolhardy enough to enter a fairy ring. Trespassers would be struck blind or lame, or even disappear to become slaves in the fairies' underground realm. In Wales the rings were associated with fertility and doom, and anyone foolish enough to plow one up would incur the wrath of the fairies. It was also widely believed that if animals grazed within a fairy ring their milk would putrefy.

On the positive side, fairy rings were said to bring good luck to houses built in fields where they occur. In another tradition, the rings were sites of buried treasure, but there was a catch—the treasure could only be retrieved with the help of fairies or witches.

The name fairy ring comes from an old folk-tale. People once believed that mushrooms growing in a circle followed the path made by fairies dancing in a ring. Fairy rings are found in open grassy places and in forests.

In grass, the best known fairy ring fungus has the scientific name Marasmius oreades. The body of this fungus, its mycelium, is underground. It grows outward in a circle. As it grows, the mycelium uses up all of the nutrients in the soil, starving the grass. This is the reason a fairy ring has dead grass over the growing edge of the mycelium. Umbrella-shaped fruiting bodies, called mushrooms, spring up from just behind the outer edge of the mycelium.

Large rings are created when the older mycelium in the center finally exhausts the soil nutrients and dies. On the death of the central mycelium, the nutrients are returned to the soil and grass can grow again.

The living edge of the mycelium continues to grow outward. As it grows, it secretes chemicals into the ground ahead. These chemicals break down the organic matter, releasing nutrients so that the mycelium will have food when it reaches this area. For a brief time, the grass at the outer edge of the ring also benefits. The extra nutrients make the grass darker green, taller, and thicker than the rest of the lawn or pasture. This lush grass dies when the mycelium grows under it and steals the nutrients.

Fairy rings made by fungi like Marasmius oreades are called "free" rings. They will continue to grow outward until a barrier is reached. Sometimes the barrier is another fairy ring! Rings can grow into each other's territory and die as each reaches the other's "dead zone."

If there are no barriers, free rings can grow outward at up to 8 inches (20 cm) per year. They can reach a diameter of over 30 feet (10 m). One ring formed in France by the fungus Clitocybe geotropa is almost a half mile (600 m) in diameter. This ring is thought to be 700 years old.

Mycorrhizal fungi, which live in symbiotic partnership with trees, also form fairy rings. Their rings are called "tethered" rings. A tether is like a leash. The fungus and its mycorrhizal partner tree need each other to survive. The mycelium of these fungi always remains joined to the tree's roots. Roots are the "tether" that keeps the fairy rings of mycorrhizal fungi from growing too far from their tree.

Fairy rings appear in any lawn, golf course or other turf areas during spring and summer months. The rings appear as either dark green or brown circular bands ranging in size from a few inches to 50 feet in diameter. The fairy ring fungus grows outward from a central point at a rate varying from a few inches to as much as several feet a year. Where several distinct rings converge, fungus activity stops at the points of contact. As a result, the circular shape of the original rings is replaced by a scalloped effect.

Mushrooms frequently develop in a circle outside of the dark green or brown ring during spring and fall after a period of heavy rainfall or irrigation. Centuries ago people thought that the mushrooms appeared where "fairies" had danced the night before-hence, the name, fairy ring.

Disease Cycle. The disease is caused by any one of a number of soil-inhabiting fungi. Development of the fairy rings starts with a germinating spore or a strand of mycleium and grows outward in all directions. The fungus feeds on organic matter in the soil. Fungal strands (mycelium) spread throughout the soil to a depth of 10 to 12 inches. As the fungus grows, the first visible evidence of a new fairy ring is a cluster of mushrooms (the fruiting structure of the fungus) or a tuft of stimulated dark green grass. Later, as the fungi spread outward from the point of origin, the ring-like pattern develops.

The initial tuft of dark green grass and the ring of stimulated grass that develops later result from the nitrogen released after the fungus breaks down the organic matter in the soil. Ae ring of brown or dead grass may also develop, caused by the depletion of soil moisture in the area where the fungus is concentrated. If you dig into the area of brown or dead grass, you will find a dense growth of white mycelium. Water will not penetrate this zone of dense mycelial growth.

During periods of unfavorable conditions, low temperatures and drought, mushroom production and fungal activity stops and may not be resumed for months or years.