Do mushrooms hurt my lawn?

Fairy ring fungi; note the circular ring, dark green grass along the margins of the ring, and weeds inside the ring. | Stock photo

Various types of fungi live in the soil and help decompose organic matter. They silently do their part to help nutrients cycle through the ecosystem. Homeowners may notice an uptick in the number of mushrooms found in their lawn this time of year.

Mushrooms are the above-ground fruiting bodies of fungi that live in the soil. They seem to sprout up overnight when conditions are ideal for spores to survive, during wet weather in the spring and fall, or if too much water is being applied through irrigation.

Toadstools, mushrooms or puffballs of various shapes and sizes are common fungi found in lawns. Their growth often appears in a circular shape because fungi grow from a central point outward. Each year the fungus grows, the circle gets bigger. Most mushrooms do not damage the lawn, but fairy ring fungi can be a problem.

Fairy Ring Fungi

Several species of fungi can cause fairy rings in lawns. Fairy rings are large rings of dead grass with darker green grass and mushrooms on the inside or outside of the ring. Fairy rings are more severe in sandy soil with low fertility. Grass on the inside of the ring is less thrifty and can easily be replaced by weeds and weedy grasses.

Management of Fairy Ring Fungi

Proper irrigation and nutrient management are the key to managing fairy ring fungi. Healthy grass requires adequate amounts of fertilizer and deep and infrequent waterings. When we have daily rain showers like we have been experiencing this spring, sprinklers should be used minimally.

In areas where fairy rings have been identified, rake and loosen the soil in the affected area. Aerate the soil and water the area deeply. After rewetting the soil reseed affected areas and fertilize.

In severely damaged areas, remove the sod, mix soil in the affected areas six to eight inches with a rototiller and reseed or put new sod in the area.