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The cause of mushrooms and brown rings in your yard and how to get rid of them

In the Garden

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Lance Ellis |

You walk onto your lawn during the spring and summer and start noticing either little rings of small mushrooms or light brown rings in your lawn. You may wonder what happened or what was accidentally sprayed on the lawn to cause this.

It is not a chemical spray or fertilizer spill. These are called fairy rings or pixie rings.

They get their name from medieval times when it was believed that these rings were created by fairies or pixies that danced around in circles during the night after everyone was asleep. There is a superstition surrounding them. Many people believe that if you jumped in and out of the ring several times it would bring the person good luck. These folklore stories do little to resolve the unsightly damage caused by these fungi.

These rings are caused by fungi in the soil that begin by sending up mushrooms in the spring and then as the summer heats up, the mushrooms die out and leave brown rings in the lawn. These mushrooms are caused by tiny threads of mycelia fungus four to six inches below the soil. Under a microscope they look like strands of spaghetti, and in unquantifiable amounts. These mycelia strands create an impervious layer down in the soil which prevents good root development of the grass. These rings of fungus down in the soil can expand and grow over the years and become chronically damaging to that area of the lawn. If left untreated, the grass in the middle of the ring will die out and become filled with weeds.

The fungus also produces gases which kill off the lawn and create a brown ring of dead grass. Strangely, most people don’t realize that this is happening in their lawns till they see a dark green ring in the lawn. The dead brown grass within the ring decomposes over time and releases nutrients in the soil. The grass on the edge of the ring becomes a darker shade of green because of the now available extra nutrients.

In severe cases where the grass has been choked out by this problem, it may be necessary to remove the top 10 to 12 inches of soil and infested turf and bring in fresh loam soil. For the majority of homeowners this is not necessary.

In an average lawn setting, aerating is the best treatment for fairy rings. Aerating is where holes are punched into the soil and turf grass and a plug of soil, grass roots, and leaf blades are brought out, which will naturally break down through decomposition, given sufficient water, temperature, and time. By aerating, you break up the impervious layer of mycelium and allow air, water, roots, and nutrients back into the soil.

For fairy rings, it is best to aerate deep. Twelve inches is the recommended depth with a distance of 8 to 12 inches between holes around the edge of the fairy ring. This should be done every spring and fall for four to five years after you have found fairy rings in your lawn.

Most lawns in our area would benefit from being aerated annually, but only to a depth of two to three inches, and not to the depth recommended for fairy rings. Following the aeration treatment for the rings, apply a fertilizer recommended for the lawn in the correct amount. If you aerate in the spring, make sure to irrigate aerated areas of lawn during hot or drought times of the summer. The aerating process is a little hard on the grass stand, and it takes time for it to recover. For this reason, aerating in the fall, rather than spring, is the preferred time of year.

Fairy rings can take a long time to control, so don’t give up hope if they keep coming back. For further questions about lawn issues, contact Lance at (208) 624-3102.