Mushrooms, also called toadstools or puffballs, live on organic matter buried in the soil. The mushroom is the aboveground fruiting or reproductive structure of a fungus that lives on and helps to decay the organic matter. The organic matter may include buried logs, lumber, roots, or stumps. Most mushrooms do not damage the lawn but are objectionable because they are unsightly. Mushrooms growing in circles of dark green grass, called fairy rings, may make the soil impervious to water and injure the grass.
There is no practical or permanent way to eliminate mushrooms. When buried wood is completely decayed, the mushrooms will disappear. The easiest and most practical solution, although it is only temporary, is to break the mushrooms with a rake or lawn mower.