This cosmopolitan weed may have been native to both eastern North America and eastern Asia (FNA 21). It is somewhat varied in morphology and chromosome number (with 2n = 24 and 72); segregates have not been recognized in recent literature but deserve investigation. Although bipinnata has been mapped as an "invasive species" by SE, this may be misguided; The species has already saturated its niche across southeastern states, from whatever source. Compared to other species of Ky., bipinnata (like its tropical relative, pilosa) has relatively long linear-fusiform seeds ("cypselae"), up to 12-15 mm (versus mostly 5-10 mm), especially the inner ones; also, inner cypselae are more-or-less equally 4-angled, thickest near the middle and equally tapered to both ends (versus more or less flattened, thickest towards tip).