This spreading rhizomatous species is widespread in northeastern regions, typically in dry woods and openings on medium acid soils. Together with lucorum, amplisquama and most communis, it is distinguished from the albicans group by its globose to obovoid perigynia (versus ellipsoid). Also, perigynia of pensylvanica tend to be thicker (1.1-1.7 mm versus 0.8-1.2 mm); staminate spikes tend to be thicker (1.3-4 mm versus 0.8-1.8 mm); pistillate spikes tend to be more separated along the culm (the lowest by ca. 8-12 mm versus 0-7 mm). Rhizomes are usually distinct: ca. 4-10 cm long versus 0-0.5 cm in typical albicans (but 2-7 cm in var. australis = C. physyrhyncha). Some colls. can be hard to distinguish from albicans, especially if immature. Hybrids are not confirmed, but 2n = 36 in both species (FNA 23). Colls. of pensylvanica that lack distinct rhizomes (due to growing conditions or poor coillecting) can also be confused with communis, which tends to be more robust in general, with larger perigynia (2.7-3.8 x 1.2-2.6 mm versus 2.2-3.4 x 1.1-1.5 mm) and wider leaves (1.8-5 mm versus 0.5-3.6 mm). A southern Appalachian segregate of pensylvanica with smaller perigynia and narrower leaves has been recently recognized by W et al.; it is expected in Ky.