This ranges widely across most of the United States but is most common in the Great Plains. Some colls. from Ky. may need to be rechecked for the more northeastern macilentus. There may be occasional hybrids with schweinitzii, lancastriensis or perhaps other species (FNA 23). Also, there has been some confusion with C. filiculmus Vahl. of the southeastern Coastal Plain (W). The lupulinus-schweinitzii complex includes high polyploids; 2n = 164-170 in most reports.