The Centaurea jacea complex is European in origin, and is a difficult group comprised of three species- C. jacea, C. nigra, and C. nigrescens, and the nothospecies C. x moncktonii. For a good synopsis of this complex see Keil & Ochsmann in Flora of North America Vol. 19, 2006 pp. 186-187. The map reflects data from all these taxa. Preliminary examination of specimens at BKL suggest that C. nigrescens is the most common entity in our area; but further research is needed.
