After a hot, dry summer, the rains finally returned. The refreshing break revived our thirsty gardens, but it also brought life to an unwelcome addition to our yard – mushrooms. The unsightly fungi magically appeared in lawns and flower beds throughout the neighborhood, and many appeared in the form of fairy rings.

Fairy rings in lawn

Although they’re unsightly, fairy rings don’t do any real damage to a yard.

Photo Credit: Gerald L. Klingaman

Fairy rings

These green swirls in the grass are caused by the extra nitrogen produced as the mycelium advances outward. A bit of extra fertilizer and water will disguise the problem.

Photo Credit: Gerald L. Klingaman

Three fairy ring mushrooms

You should consider all wild mushrooms poisonous unless their identity is confirmed by a knowledgeable expert.

Photo Credit: Gerald L. Klingaman

While “fairy rings” may sound pretty, they’re not. They’re just the result of mycelium – or the vegetative body of a mushroom colony – that originally started growing on a piece of underground organic matter, like a dead tree stump or root. As this underground organic matter decays, mycelial strands begin to radiate outward. A sudden increase in moisture (like recent rains) can cause the strands to get reproductive and produce a mushroom – especially when rain is combined with the right soil temperature.

If soil is fairly consistent and moist – like you often find in lawns – you might see a fairy ring form a complete circle. Other times only a portion of the circle’s circumference will grow. These partial, often eyebrow-shaped remnants are more common than full circles.

Of course, this process of decay and underground expansion of fungi mycelium doesn’t go unnoticed in the lawn. In addition to the actual mushrooms, the grass inside the fairy ring usually is less vigorous than the rest of the lawn. Sometimes it browns out because the mycelial mat is so dense that grass roots can’t get the water they need. On the outer extremity of the fairy ring, however, the mycelium is nutrient-rich – especially in nitrogen – so the grass there will be greener and taller than the rest of the lawn.

While fungi fairy rings can disrupt the carpet-like nature of a lawn, they don’t cause any lasting damage. Removing tree trunks and other buried-underground debris can help prevent fairy rings from forming. Grinding root stumps may slow down the formation of fairy rings, but the large roots that remain after the stump is ground up can still serve as a source for mushrooms. Digging out the buried roots might be justified in extreme cases, but this usually causes more lawn disruption than a fairy ring.

Some other things you can do to reduce the fairy ring effect in your lawn is to run an aerator through the mycelial matt to break up the mycelium and improve water percolation in the soil. A dose of extra fertilizer and water within a ring area can help revive grass in the interior of the ring. You can also try removing the mushrooms as soon as they appear. It’ll make your lawn look better and may reduce the number of spores, but it won’t impact the spread of the mycelium.

The most important thing to know about fairy rings is not to eat any of the mushrooms they produce. Just about any kind of mushroom can potentially make a fairy ring – some are edible, but most will kill you graveyard dead! In fact, all wild mushrooms should be considered poisonous unless their identity is confirmed by an experienced mycologist. Remember this: “There are bold mushroom hunters, there are old mushroom hunters, but there are no old, bold mushroom hunters.”

In the end, the fairy rings will eventually go away on their own. As long as your children or pets don’t bother them, they’re nothing to worry about – just unsightly to look at.