This is a variable annual (2n = 24, 48), widespread in temperate regions of North America and Eurasia, but described segregates (e.g. F) have not been recognized in recent treatments (e.g. FNA 21). Var. elliptica Wieg. was described from BELL (M), and F treated it as a relatively northern segregate that hybridizes with connata. In some early literature (e.g. Gm), cernua has been misidentified as laevis, which may also intergrade; see notes under laevis.