Fairy rings may appear in various ways on lawns. Circles or arcs of dark green, lush, fast-growing grass are perhaps the most common, especially in spring. These rings are most commonly between 2 and 15 feet in diameter; although they may appear larger or smaller. Mushrooms or puffballs may appear under wet conditions in this same ring pattern. In some cases, a ring of brown or dead grass may appear.
Fairy ring fungi are not attacking the grass directly but are breaking down organic matter in the soil. As a result, nitrogen is released that the grass above may use, causing the green ring. In cases where the mycelia of the fungus get dense and inhibit water movement into the soil, grass inside the ring may turn brown. Mycelia may also deplete soil nutrients and produce toxic levels of hydrogen cyanide. The mushrooms that appear after rainfall are the fruiting bodies of the fungus.