Fairy Rings in Lawns/ Dark Green Circles in Lawn
The following questions were sent to the P&PDL diagnosticians here at Purdue University:
Question 1: How do you get rid of mushrooms that grow among the grass? The mushrooms are in a ring of approximately 4 ft. diameter.
Question 2: How can you get rid of fairyring besides digging up the ring and replacing the soil and sod?
Question 3: There are dark green circles in my lawn. What are they and what should I do about them?
Answer: These descriptions are typical of fairy rings caused by a diverse family of fungi called basidiomycetes. Fairy rings might be six inches to two feet wide and can be anywhere from two feet to hundreds of feet in diameter and expanding yearly.
The presence of mushrooms usually indicates an organic source of nutrients, such as a buried tree stump, is nearby. When you see a mushroom growing in a lawn, you are only seeing a small part of the fungus. The fungus also grows underground as a thread-like mass that is called mycelium. This mycelium tends to grow in all directions from a central point. Thus, an invisible circular pattern occurs. The fruiting bodies (mushrooms) then tend to appear in a circular pattern.
The term "fairy ring" comes from a superstition that the mushrooms growing in a circle represent the path of dancing fairies. Usually on the inside of the fairy ring, a dark green ring of grass will be evident. This is because extra nitrogen is available in that area where the fungal mycelium has died.
There is no good control for fairy ring. Mushrooms can be temporarily removed by regular mowing or raking. Since fairy rings are most visible on low fertility conditions, you can mask the fairy rings by regular applications of low rates of nitrogen.
-Peggy Sellers and Zac Reicher