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Scleroderma polyrhizum

by Michael Kuo, 1 July 2025

In my little Midwestern town, Scleroderma polyrhizum is Nature's way of getting back at urban development. We have a subdivision called "Heritage Woods," built by a developer in the 1970s who leveled acres of natural trees to build split-levels with prominently featured garage doors for middle-class white people ("Heritage") who then planted ornamental, non-native, four-foot saplings to decorate their yards ("Woods").

But Scleroderma's Revenge has been popping up all over the place ever since. When young, the tough, baseball-sized mushrooms wreak havoc with lawnmower blades; in maturity they split and spread open, creating unsightly black lawn-sores near sidewalks—plump pustules on patiently preened promenades.

Here's to the dandelions, who will always come back! Here's to Pluteus petasatus, fruiting from buried roots by the dozens, years after the City has removed the tree ("What if my kid touches it?" "The dog ate one!" "How do I kill these mushrooms??!!"). Osama bin Laden has attacked New York; we'd better remove the "Virtual Tour" of the Charleston, Illinois water plant from the Internet, so he can't figure out how to poison us! Tik-Tok will ruin our children!

And here's to Scleroderma polyrhizum. Identifying features include the baseball-like stature and shape; the tough, thick skin; the hard, black interior that turns to dust in old age; the way the mushroom splits open and peels back (a little like the rays of a star); the smooth to pocked or pitted (but not prominently scaly) surface; and the habitat in grass and disturbed-ground settings.

Scleroderma polyrhizon is a synonym. Scleroderma bermudense, Scleroderma geaster, Scleroderma guzmanii, Scleroderma yunnanense (and possibly Scleroderma anomalosporum, Scleroderma sinnamariense, and Scleroderma xanthochroum) should be treated as synonyms pending further research; a preliminary investigation of this group by Ortiz-Rivero et al. (2021) is so full of errors, inconsistencies, and poor documentation that its findings should be regarded as suspect and the best course, for now, is to place all of these putative species under the polyrhizum umbrella.

Thanks to Joanne Bilarczyk for collecting, documenting, and preserving Scleroderma polyrhizum for study; her collection is deposited in The Herbarium of Michael Kuo.

Description:

Ecology: Probably saprobic, but possibly mycorrhizal; growing alone, scattered, or gregariously in grass and in disturbed-ground settings; often appearing in urban settings; summer, fall, and early winter; originally described from Italy (Micheli 1729); widely distributed in Europe and North America; also reported from the Caribbean, Central America, northern Africa, Asia, and Oceania. The illustrated and described collections are from Illinois and New Jersey.

Fruiting Body: At first 8–13 cm across, spherical to cushion-shaped; with maturity splitting near the top and peeling back in irregular rays, becoming star-shaped, or shaped like a ragged-edged bowl, up to 30 or more cm across; surface whitish to brownish or brown, bruising yellowish to reddish, when young fairly smooth and often covered with whitish down, but with age becoming pocked, pitted, or minutely scaly in places, and often covered with adhering soil and debris; rind 2–6 mm thick, whitish, when sliced usually blushing reddish; spore mass at first hard and purple-black, becoming blackish to dark brown and powdery; without a pseudostem, but pinched at the point of attachment; base attached to whitish to yellowish rhizomorphs (the epithet polyrhizon means "many-rooted," a reference to the rhizomorphs).

Odor: Not distinctive.

Chemical Reactions: KOH negative to yellowish on surface.

Microscopic Features: Spores 6–10 µm excluding ornamentation; globose or subglobose; ornamented with spines 0.5–1.0 µm long and scattered to frequent connecting ridges; partially reticulate, or sometimes not reticulate; golden brown in KOH. Peridial hyphae with clamp connections.

REFERENCES: (J. F. Gmelin, 1792) C. H. Persoon, 1801. (Micheli, 1729; Coker & Couch, 1928; Smith, 1951; Guzmán, 1970; Smith, Smith & Weber, 1981; Guzmán-Dávalos & Guzmán, 1985; Weber & Smith, 1985; Arora, 1986; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Sims, Watling & Jeffries, 1995; Miller & Miller, 2006; Boccardo et al., 2008; Kuo & Methven, 2010; Guzmán et al., 2013; Kuo & Methven, 2014; Siegel & Schwarz, 2016; Kibby, 2017; Woehrel & Light, 2017; Elliott & Stephenson, 2018; McKnight et al., 2021; Ortiz-Rivero et al., 2021.) Herb. Kuo 09170501, 01030801, 01011201.

This site contains no information about the edibility or toxicity of mushrooms.

Spores

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Cite this page as:

Kuo, M. (2025, July). Scleroderma polyrhizum. Retrieved from the MushroomExpert.Com Web site: /scleroderma_polyrhizum.html