Many Iowans have recently noticed large, white fungal spheres emerging from the ground in lawns, prairies, and forests. These puffballs are the fruiting structure of a fungus, and come in a variety of sizes.
Perhaps the most common species of puffball is the giant puffball, Langermannia giganteum (formerly Calvatia gigantea). This puffball can grow up to a foot or more in diameter, appearing as a large, white ball. At first it has the texture of a marshmallow, but as the puffball matures it turns olive-brown, and the interior becomes spongy and filled with spores. Giant puffballs are not harmful and are in fact edible when young and white inside. However, you should cut the puffball in half before eating it to make sure it does not have a stalk inside; young deadly Amanita mushrooms look similar to puffballs from the outside.
Another common puffball is the hard puffball (Scleroderma sp.), also called an earth ball. Hard puffballs are round, about the size of a tennis ball or slightly larger. Unlike giant puffballs, hard puffballs develop just underneath the surface of the soil. When they mature, they open up revealing spores inside, and this develops depressions in the soil surface, causing the lawn to be bumpy.
Puffballs are not harmful to people, pets, or plants, but can be a nuisance in well-maintained lawns. There is no feasible management for them other than removing the fruiting bodies as they appear.
More information about mushrooms and other fungi in Iowa can be found in NCR 129, Mushrooms and Other Related Fungi.
Giant puffball (Lois Tiffany/George Knaphus)