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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Gardening: Removing fairy rings takes work and patience

Fairy ring mushrooms are the fruiting bodies of soil fungi that form dark green rings in our lawns. As the fungi break down organic material in the soil, they release nutrients that green up the grass.  (Courtesy of Washington State University)
By Pat Munts For The Spokesman-Review

Even though it has been a bit dry this spring, the conditions are still right for fairy ring mushrooms to pop up in our lawns.

The circle of mushrooms we see in the lawn are the fruiting bodies of fungi that naturally live in the soil. Fungi have been around for millions of years, and their simple biology doesn’t respond to easy fixes to remove them. It is going to take work and time to accomplish this.

The fungi naturally live on woody and organic debris found in the soil. This debris is often left over from a construction project or from stumps and tree branches that were buried in the soil. They can lie dormant for years before the conditions are right to emerge.

The fungi develop underground as a dense, white, thread-like mass called mycelium. As the mycelium grows, is breaks down organic matter and releases nutrients into the soil that are picked up by the grass, forming dark green circle in the lawn. The green circle continues to expand as the mycelium advances, leaving behind a mat of weakened or dead grass in the center underlain by a dense filament mat of dead mycelium.

There is no quick or easy cure for fairy rings. They are more common in poorly maintained, drought-stressed lawns on light sandy soils. Don’t be tempted to try lime, salt, fungicides or other quick-cure remedies. They don’t work. The only way to eliminate the problem is to get water through the filament mat.

The following method for removing them was developed by Washington State University and will involve some work, about a month of time and paying attention to details.

1. First, rake or mow the mushrooms off the lawn and throw them in the trash. They are harmless.

2. Using a spading fork or a crowbar, poke 3-inch-deep holes in the soil over the entire ring to open holes through the mycelium. Punch as many holes as you can, moving the fork or bar back and forth as you do to break up the soil profile further. Core aerating with a machine isn’t effective because coring tubes are too short to give complete penetration.

3. Apply a mixture of liquid dish soap or a commercial surfactant and water to the area. The soap or surfactant breaks down the surface tension of the water and helps it penetrate the soil. Use one teaspoon of soap per gallon of water and liberally pour several gallons on the ring. The soap will not hurt the grass or kill the fungi.

4. Flood the area thoroughly with plain water with a hose to create a pool of standing water. Do not use a sprinkler – it will not get enough water on the lawn to be effective.

5. Repeat steps two, three and four every three days for four weeks. The fairy rings will begin to disappear after about two weeks. Reseed the area if necessary. This process, though tedious, does work.