I’ve seen two postings with photos of Fairy Rings on Facebook this week, so there is an apparent outbreak of them, likely caused by all the rain we’ve gotten lately. Fairy rings are those peculiar sprouting up of mushrooms in a well-defined arc or circular pattern. This has caused a lot of myths about their origin to sprout up over the centuries, but there is an explanation as to what’s going on with the rings.

First, a review of the life of mushrooms, or I should say fungi. The main body of a fungi is not obvious, existing as millions of tiny white filaments in the soil called mycelium. These filaments penetrate, break down and consume organic matter in the soil. The mushrooms that appear on the surface are merely the fruit of the underground fungal body, and their only purpose is to release seed spores to spread the fungi to other places.

So, fairy ring formation goes something like this: normally they get started where there is a lot of organic material in the ground, such as decaying roots where a tree once stood, or buried woody debris. The underground fungi feed on this material, and as it depletes the supply, new mycelium move outward seeking more food, while the old mycelium dies due to lack of food. This outward movement of certain species of fungi is in a circular pattern like a donut. Occasionally, during rainy conditions, the fungus will decide to be fruitful and multiply, sending up mushrooms that form the visible circular pattern we call fairy rings. There are around 50 species of fungi known to form Fairy rings in grassy areas.

Sometimes, the grass growing over the fungus will grow more lush with a darker color, again in a circular pattern. This is caused by the fungus decaying organic matter and subsequently releasing nutrients that makes the grass grow lusher. Sometimes, the grass over the fungus will turn brown, also in a circular pattern, caused by the mycelium being over-populous and depleting nutrients and water resources. As long as there is material to feed on, fairy rings will continue to grow in ever wider circles, moving on average around 3-20 inches per year.

Plants growing in such a district pattern made folks back in the day think that they were supernatural. One myth is that the circle is where fairies, witches, or elves gather to dance, and it was considered very unlucky to step inside the ring. A Dutch superstition is that the ring is where the devil set up his milk churn.