This tetraploid (2n = 60) is widespread in eastern North America, and one of the commonest species of Cuscuta in Ky. It occurs on many hosts in diverse habitats, but usually on damper soils than pentagona and flowering a month or so later in Jul-Sep (F; D. Boone, pers. comm.). It has a distinctive stylopodium (thickened ridge at base of style); but see also rostrata (W; Spaulding 2013b). Other differences from pentagona (and campestris) include: corolla lobes mostly obtuse and straight at tip (versus acute and inflexed); flowers and fruits often glandular with translucent laticifers; calyx surface usually without noticeable reticulation (versus usuallly distinct). In addition to typical gronovii, var. latiflora Engelm. is expected in the state but colls. have not been checked. That taxon differs in its relatively elongate, less overlapping calyx lobes, and shorter corollas with more elongate lobes, resembling C. polygonorum (Costea et al. 2006b). The related species, C. obtusiflora Kunth., is known mostly from Gulf Coastal states and the West Indies, but it extend north at least to s. Mo. (Ladd & Thomas 2015). C. obtusiflora has been reported from Ky. (Hoagland & Jones 1992), but not verified, and it was later excluded by J (see also W and citations). See Spaulding (2013b) for clarification of differences from gronovii.