Sometimes mushrooms will develop and form large circular patches in lawns. Each year the circles are likely to expand. When these circles or "Fairy Rings" are small there may be no effect on the grass, but as they continue expanding, a zone forms where the mushrooms come up. Inside this is an area of poor grass growth, or even dead grass.
Fairy Rings are unsightly and difficult to control. Many homeowners may prefer to live with the problem. One way to eliminate Fairy Ring is to dig it out, although this is usually far from being practical. If you do decide to take this route, mark out an area at least one foot beyond the ring and remove all sod in that area. Remove all the soil in that area to a depth of one foot, being careful not to spill any on the lawn. Refill the hole with new soil and reseed or re-sod. Seeding is preferable as there is less danger of reintroducing the Fairy Ring fungi. Doing this job without spilling any soil and reintroducing the Fairy Ring fungi is extremely difficult.
For those who decide to live with this problem, there are several ways to minimize damage to the grass in Fairy Rings. The grass should be fertilized with nitrogen several times a year to help mask symptoms. Nitrogen should be applied during the growing season.
Most of the Fairy Ring growth (a fungal mat) is in the ground underneath the Fairy Rings. As the ring expands the fungal growth begins forming a dense mat of dead material that creates a water-resistant layer. Penetrating this layer will help moisture reach the turfgrass roots. This can be done in several ways.
Using a "root feeder" attachment on a garden hose, punch holes at least every foot in the yellowing or dying area and pump large amounts of water into the ground to a depth of 10" - 24". Repeat frequently. Increasing the soil moisture may also change the ecological balance enough to retard the growth of the Fairy Ring fungi.
Aerating the lawn several times during the growing season is also possible. When aerating over the infected area, repeat the aeration process several times.
Whichever method is used, applying a wetting agent to the area may also increase soil permeability and help to lessen symptoms.