Photo 1: Newly emerging lawn mushrooms. Bob Mugaas
Bob Mugaas, University of Minnesota Extension Educator
With some areas of the state receiving moderate to heavy amounts of rainfall over the past couple of weeks, mushrooms are beginning to randomly appear in lawns. Their appearance often causes people to be concerned about the health of their lawn and whether or not a serious disease might be getting started.
It’s important to remember that mushrooms are the ‘fruiting bodies’ of fungi living in the soil and thatch. They are responsible for the production of microscopic spores that in turn help propagate the fungus. The vast majority of those fungi are not associated with any lawn disease causing organisms. It’s quite common for them to appear during periods of moist conditions resulting from either natural rainfall or excessive irrigation. Again, they are not necessarily indicative of any particular lawn problem. The fungi are living on decaying organic matter in the soil and/or thatch layers. This breakdown of organic matter results in at least some of the nutrients contained in that organic matter being released back to the soil. At that point the nutrients are available for continued plant growth or used by other microorganisms. If you find the mushrooms offensive, simply knock them over with a rake and remove them from the area.
Photo 2: Typical lawn ‘fairy ring’ symptom. Bob Mugaas
The one exception to the above situation is a lawn problem known as fairy ring. Symptoms in the lawns appear as dark green arcs and/or circles; often darker than the surrounding grass on either side of the ring or arc. There are a number of different fungal organisms associated with the production of these arcs or circles. If you suspect this problem is in your lawn please view this link on fairy rings which is part of the diagnostics feature on the University of Minnesota.
You might also want to visit the University Of Minnesota Extension on Gardening for all sorts of great information on gardening and more; http://www.extension.umn.edu/garden/