This is centered in the lower Mississippi Valley, but extends west at least to Ala., c. Tenn., c. Ky and s. Ohio (FNA 23, W; Mohlenbrock 2011). Compared to typical tribuloides, its perigynia are less elongated (with L/W = 2.2-3 versus 3-5). Also, it tends to have a more elongated inflorescence (with separated spikes versus clustered), and narrower leaves (ca. 2-4.5 mm versus 3-7 mm) without an expanded sheath summit. It mostly occurs in wooded seeps and swamps (versus more open habitats), often becoming locally dominant with rhizomatous vegetative shoots. Although some of these plants were previously identified in Ky. as the northern species, projecta (= C. tribuloides var. reducta Bailey), sangamonensis is now considered closer to cristatella (Hipp et al. 2007; A.A. Reznicek, pers. comm.). See also notes under projecta.