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Scleroderma verrucosum

by Michael Kuo, 3 June 2025

Like other earthballs in the genus Scleroderma, Scleroderma verrucosum has an interior that is initially white and soft, but hardens and becomes purplish black with maturity, eventually turning into spore dust. However, the species can be separated with a combination of features: it generally appears in hardwood forests; the surface develops small brown scales, and fresh specimens bruise pink to red when handled; a drop of KOH turns the surface pink to red; and, under the microscope, the spores measure 6–10 µm (excluding ornamentation), and are not reticulate.

Scleroderma areolatum also appears in hardwood forests and is very similar, with the exception of the spore measurements; areolatum has larger spores, measuring 10–14 µm (excluding ornamentation). According to some authors (especially in Europe) verrucosum is more likely to develop a robust pseudostem, and is a little larger—but I have not found these differences to be clearly and consistently correlated with spore size in my North American collections.

Description:

Ecology: Mycorrhizal with oaks and possibly with other hardwoods; growing gregariously from spring through fall, or over winter in warm climates; originally described from France (Bulliard 1791); widely distributed in Europe and North America; reported from Africa, the Caribbean, Central America, South America, Oceania, and Asia. The illustrated and described collections are from Illinois and Missouri.

Fruiting Body: 1–4 cm across; more or less round; surface whitish to yellowish or brownish, sometimes bruising pink or red, with small, brown, adnate scales; rind about 1 mm thick, white, staining slowly pink when sliced; spore mass white and fleshy at first, becoming purplish gray to black and eventually powdery; pseudostem often present, 1–3 cm long, whitish; with white rhizomorphs attached to the base.

Odor: Not distinctive.

Chemical Reactions: KOH pink on surface, sometimes after a yellow reaction.

Microscopic Features: Spores 6–10 µm excluding ornamentation; globose to subglobose or occasionally broadly ellipsoid; densely spiny with spines 1–3 µm long; not reticulate; golden brown in KOH. Clamp connections not found in peridial hyphae.

REFERENCES: (J. B. F. Bulliard, 1791) C. H. Persoon, 1801. (Guzmán, 1970; Phillips, 1981; Guzmán-Dávalos & Guzmán, 1985; Schalkwijk-Barendsen, 1991; Sims, Watling & Jeffries, 1995; Boccardo et al., 2008; Trudell & Ammirati, 2009; Buczacki et al., 2012; Guzmán et al., 2013; Gminder & Böhning, 2017; Kibby, 2017; Jeppson, 2018; Pinzón Osorio et al., 2018; Læssøe & Petersen, 2019.) Herb. Kuo 09180404, 09160604, 08281902, 07282204.

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Spores

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Kuo, M. (2025, June). Scleroderma verrucosum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/scleroderma_verrucosum.html