Identification, Introduction, Distribution, Ecology, and Economics of Centaurea Species

Abstract

Numerous Old World Centaurea spedes (knapweeds and starthistles) have naturalized in western North America and are recognized by various states and provinces as noxious weeds. The fifteen species discussed in this paper include spotted knapweed (Centaurea maculosa), diffuse knapweed (C. diffusa), squarrose knapweed (C. virgata ssp. squarrosa), Russian knapweed (Acroptilon repens), yellow starthistle (C. solstitialis), bighead knapweed (C. macrocephala), short-fringed knapweed (C. nigrescens), brown knapweed (C. jacea), black knapweed (C. nigra), meadow knapweed (C. jacea × C. nigra), featherhead knapweed (C. trichocephala), purple starthistle (C. calcitrapa), Iberian starthistle (C. iberica), Malta starthistle (C. melitensis), and Sicilian starthistle (C. sulphurea). Within this genus, the species evolved diverse adaptations to different conditions of environment and disturbance in Europe and Asia. These adaptations foster their success in the new environments of North America, but it is apparent that each species must be managed differently because of differences in ecologic amplitude, response to disturbance, and methods of dispersal and establishment. This paper summarizes the introduction, distribution, and ecology of knapweeds and starthistles in western North America and includes a key for identification of the species.