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Gardening: Hard work required to remove fairy rings from lawn

It’s been a bit dry this spring but not enough to stop fairy rings from popping in our lawns.

Fairy ring mushrooms are the fruiting body created by any one of dozens of fungi that live on rotting, woody material in the soil. They are one of the oldest life forms, and their simple biology has allowed them to survive millions of years of change. Sorry folks, there is no quick fix on this one; getting them out of your lawn isn’t going to be easy.

The woody debris is often left over from a construction project or stumps and tree branches buried during a land clearing or building project. Fungi spores that invade the debris develop into a dense, white thread mass – mycelium – that spreads underground. As the mycelium grow outward, they help release nutrients into the soil that are picked up by the grass above. As the fungi advance, the green zone moves out and leaves behind an ever-enlarging patch of weakened or dead grass and a very dense filament mat. Poorly maintained, drought-stressed lawns on light, sandy soils are often the most effected; lawns with a heavy thatch buildup are particularly susceptible to the fungi. The mushrooms that appear are the fruiting body of the underground fungi.

There is no quick or easy cure for fairy rings. Don’t be tempted to try lime, salt, fungicides or other supposed quick-cure remedies. The only way to eliminate it is to get water through the filament mat. This method is based on research done by scientists at Washington State University and will take about a month of time and close attention to procedures.

1. Rake the mushrooms up or mow them off with the lawn mower. They will not hurt the lawn.

2. Aerate the soil at least 3 inches deep inside the green ring with a spading fork or crowbar to open passages to the roots. Punch as many holes as you can, moving the fork or bar back and forth as you do to break up the soil profile even more. You can core aerate, but the coring tubes may not be long enough to give complete penetration.

3. Apply a wetting agent such as liquid dish soap or a commercial surfactant to help the water penetrate the soil. Use 1 teaspoon of soap per gallon of water and pour several gallons on the ring. The soap will not hurt the grass or kill the fungus; the soap breaks down the surface tension of the water, allowing it to flow more easily.

4. Drench the area thoroughly with plain water to the point of having standing water. Do not use a sprinkler – it will not get enough water on the lawn. Use a hose for large areas and buckets for small ones.

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

Pat Munts has gardened in the Spokane Valley for more than 35 years. She can be reached at pat@inlandnw