- Centaurea cyanus
Known as “cornflower” in southern Europe where this annual species is native and a common weed in grain (“corn”) fields. Bachelor’s button has striking sky-blue (sometimes purple, pink or white) pompom flowers atop 30- to 90-cm-tall, grey-green stems loosely clothed with slender leaves of the same colour. Bachelor’s buttons are frequently found as a significant component of “wildflower” seed mixes—avoid these. Seedlings grow quickly, produce copious seed and readily invade dry meadows, fields and grasslands.