Mushrooms

Questions about Fairy Rings

A reader wrote to ask me about fairy rings this past week. She wanted to know how and why mushrooms grew in rings. This particular ring was noted in a grassy area near a stream. The answer to this question lies sometimes in the type of mushroom that grows from the mycelium that forms the ring and at other times in the conditions that allow that mycelium to advance on a circular front.

Fairy-ring formations occur when a mycelium grows out equally in all directions from a central point. The advance is usually slow, and its longevity depends upon weather and ground conditions. You’ll find fairy rings most often in grassy areas, like lawns, golf courses, and old fields during warm, wet weather. These landscapes, which are often void of rocks and other barriers, allow the mycelium to progress outward in the circular movement unimpeded.

After the discovery of a fairy ring, a site that often inspires wonder and curiosity, you might want to study the surrounding area. A typical fairy ring consists of two areas of lush green grass separated by a zone of stunted growth where the mushrooms grow. The dry area, which may be completely bare of grass, is the result of filaments that produce the fruiting bodies. Although mushrooms thrive in this ring, these filaments also clog the air spaces in the soil and prevent water absorption.

In contrast, the lush area within the ring has been fertilized by those same filament remnants that have been broken down by bacteria. In turn, this reaction transforms the soil’s humus into nitrates and nitrites that stimulate grass growth. Enzymes secreted by the fruiting bodies, rather than filaments in the mycelium, produce the lush growth in advance of the fairy ring. These enzymes, or secretions, act as a fertilizer as well.

One of the most common mushrooms found in fairy rings is the gill-bearing fungus Marasmius oreades, also known as the “Fairy-Ring Champignon” or “Scotch Bonnets.” While the M. oreades is edible, the poisonous Clitocybe dealbata often is found clustered with the M. oreades. And, as the M. oreades ages, it can become difficult to tell the two species apart.

Additionally, I would be totally against eating anything that grows on a golf course or on treated lawns, as the mycelium can often absorb any chemicals used in those areas. One more warning – the M. oreades isn’t the only mushroom that can grow as a fairy ring. Other species have exhibited circular growth, including the common field mushroom (Agaricus campestris).

My final word of advice: Don’t eat the fairy ring. Instead, just sit in the middle of the ring and meditate. You’ll feel much safer and more serene in the long run…

NOTE: If you have photographs of fairy rings, let me know so that you can share that photo with readers here at fungifest!

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