Fairy Ring Mushrooms

Q:  Several years ago we noticed our lawn developed a Fairy Ring.  Each year it gets slightly bigger in diameter and occasionally produces mushrooms.  Any suggestions for getting rid of it and are the mushrooms toxic?

A:  According to CSU, all lawn grasses are susceptible to fairy rings and several species of mushroom-producing fungi may cause them. In terms of control, I'm afraid that there is little that you can do.  Fortunately, fairy rings are not harmful in any particular way. Aside from the occasional appearance of mushrooms, the most common effect of fairy ring fungus is the formation of darker green, stimulated rings of grass.

The stimulation of growth and color is caused by the release of plant nutrients to the turf as the fungus decomposes organic matter in the soil. Much less commonly, the soil just inside the ring may become so filled with the fungus that water penetration is prevented and the grass goes dormant or dies. A modest increase in organic nitrogen fertilization (ingredients like alfalfa meal, soy meal, and cottonseed meal) over the entire lawn can help mask symptoms. If fairy ring has caused significant grass death, then renovation (heavy core aeration, followed by over-seeding with the appropriate species) may be necessary.

Read our Q & As with Keith Funk answering common Colorado gardening questions here. You can also hear him on the Garden Wise Radio Show