University of Michigan - FAIRY RINGS
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.
- hyphae (hí - fee) plural: the threads that form the body of a fungus (mycelium)
- mycelium (my - sée - lee - um): see hyphae
- mycorrhiza (my - koh - rý - zuh) singular; mycorrhizae (my - koh - rý - zee) plural: a beneficial combination between a fungus and a living plant root
- symbiosis (sim - by - óh - sis) singular; symbioses (sim - by - óh - sees) plural: a partnership formed between two living organisms.
- Fogel, Robert and Rogers, Patricia. Fairy Rings. 2002. University of Michigan Herbarium. http://herbarium.usu.edu/fungi/FunFacts/factindx.htm
- If we would dig up the mycelium, it would look like a loose mat of very fine roots. But the mycelium are better competitors than the grass roots, when it comes to getting _______________.
- Most of the fungus, the mycelium, is below the soil surface. The only part we see are the above-ground fruiting bodies. We call those bodies ____________________.
- If apple trees grew like these fungi, all we'd see above the surface would be the _________.
What happens to the grass after it undergoes a period of lush growth?
- Did we see a free fairy ring or a tethered fairy ring? ___________________________
The University of Michigan fact sheet shows a cross-section (a side view cut into the ground) of a "perfect" fairy ring. Name two ways that the ring we saw wasn't "perfect".
If a fairy ring can grow outward up to 8 inches per year and our fairy ring is 16 feet in diameter, what is the youngest this fairy ring could be? Hint - draw a picture of the ring in the 1st year, then the 2nd year...
Draw a little sketch of two fairy rings that collided several years ago. Hint - think about the drawing above.