An annual Eurasian plant cultivated in North America having showy heads of blue or purple or pink or white flowers; SYN. bachelor's button, bluebottle, Centaurea cyanus.
Plant Centaurea cyanus of the family Compositae. It is distinguished from the knapweeds by its deep azure-blue flowers. Formerly a common weed in N European wheat fields, it is now commonly grown in gardens as a herbaceous plant.