The status of Boltonia decurrens (Torr. & Gray) Wood as a distinct species is strengthened by consideration of its lack of rhizomes as compared to B. asterioides (L.) L’Her var. recognita (T. & G.) Engelm. Boltonia decurrens reproduces asexually by basal shoots in addition to its seed production. Historically, B. decurrens has been limited to moist habitats along a 400 km stretch of the Illinois and Mississippi rivers in Illinois and Missouri. At present, seven populations are known from a 37 km reach of the middle Illinois River. All of the surviving populations are in man-disturbed habitats. The species is in danger of becoming extinct.