Carex vulpinoidea is widely distributed in North America and frequently grows as a weed in wet roadside ditches and fields. It is quite variable, particularly in the degree to which the spongy tissue lateral to the achene is developed. The development of that tissue determines the shape of the perigynium and the degree to which the perigynium appears to contract into the achene, as discussed by F. M. B. Boott (1858–1867). The flowering stems shorter than the leaves, the pale brown, elliptic perigynia, and the preference for moist substrates of C. vulpinoidea readily distinguish it from C. annectens.