Centaurea is a genus of herbs.
Leaves initially in a rosette, stem leaves alternate (ours).
Flowers blue-purple to pink (ours), all disk flowers (discoid) with long petal lobes but often the marginal flowers larger and irregular; basal bracts in several, overlapping rows, dry, membranous, margins fringed or ragged, expanded top of flower stalk (receptacle) with dense bristles.
Fruit dry, 1-seeded (achenes), with or without a fringe of bristles.
Origin: All of ours are exotics; many invasive.