This has a rather fragmented range, centered in east-central states and somewhat concentrated in eutrophic or calcareous habitats that have become much reduced by conversion to farmland. It is an uncommon species that is close to, and often confused with, the more widespread eastern species, lupulina. Some colls. may be intermediate. C. lupuliformis can appear somewhat transitional from lupulina to the southern species, gigantea. Compared to lupulina, its achenes have distinctly pointed or knobbed angles (versus smoothly curved), and are usually 2.4-3.4 mm wide (versus 1.7-2.6 mm), often almost as wide as long (versus clearly longer than wide). Also, perigynia tend to be more spreading (versus ascending), though not perpendicular to the rachis as in gigantea. It may be an aneuploid derivative (Hill 2006): 2n = 60 (versus 56). C. lupuliformis often grows with lupulina (Hill 2006), but it may be associated with more open native vegetation, and its rhizomes tend to be longer, potentially creating large patches in marshy areas around open water (FNA 23).