Fairy Rings

Perfect dark-green circles in the grass--can they be caused by watering or fertilizing patterns? No human could so err; perhaps a rotary sprinkler, or a spreader did the deed. That explanation won't work either, for fairy rings were observed long before the machine age. From the distant past of folklore comes the story that the narrow dark green rings are created by fairies dancing on the dew-laden grass in the moonlight.

No less fascinating is the explanation that mushroom mycelium creates fairy rings on our lawns. Mycelium is the term for the underground mass of interwoven threadlike filaments that are a part of mushrooms and other fungi. Mycelium spreads through the soil, decomposing dead grass roots and other organic material as it extends outward in circular fashion. Like fire in dry leaves, mycelium consumes what it can use in the center, and it must grow radially to acquire new fuel. Mushrooms, the fruiting bodies of mycelium, are formed at the outside edge of the actively spreading mycelium. The intense green color of the fairy ring is created by fresh fertilizer produced as humus is broken down into nutrients usable by the grass.

Air photos show fairy rings as large as 200 meters in diameter. Such large rings are thought to be more than 600 years old. Several large rings, up to 3 meters in diameter, can be seen on the University campus; some of these yield copious quantities of edible mushrooms.