This week, a homeowner in Benton County found scattered groups of the fungus in their lawn. A client submitted a sample for mushroom identification of a bumpy looking mushroom by her oak tree. What are they? Our client though maybe truffles? Maybe a puffball?. Not quite.
There are several, unrelated fungi that can produce macroscopic somewhat rounded, bump-like fungal bodies. Artificially grouped in the gasteroid fungi, all that puffballs, earthstars, and earth balls have in common their rounded shape.
The sample submitted was a Scleroderma species, one of the many mushrooms known as earth ball. Sometimes they are referred to as hard puffballs. Most Scleroderma species develop tuber like fungi, partially or completely buried in the ground. Unfortunately, some species are known to produce toxins as mentioned in various mycology books and resources.
Earth balls, Scleroderma, can be associated with trees, around logs or stumps, but also in lawns. As it matures an earthball appears as somewhat circular depression in the ground. Such depressions may be considered a nuisance on highly manicured lawns. The fruiting body of Scleroderma species is round, usually about the size of a golf ball, but some can be as big as a tennis ball. The outer covering is thick, rough, and tan to brown.
What to about them? See the answer in the article What Can I Do About Mushrooms In My Yard? On My Tree?
An excellent book that pictures and describes mushrooms and fungi found in Iowa is Mushrooms Other Fungi of the Midcontinental United States by D.M Huffman, L.H. Tiffany, and G. Knaphus. It's published through Iowa State University Press, Ames, IA 50010.