Centaurea cyanus L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Annual or winter-annual 2–12 dm, usually loosely white-tomentose when young, the lower lf-surfaces often persistently so; lvs narrow, often linear, entire, or the lower ones a little toothed or with a few narrow lobes, to 13 × 1 cm (excluding the lobes); heads terminating the branches; invol 11–16 mm, its bracts ± striate, with a relatively narrow, often darkened, pectinate or lacerate fringe near the tip; fls mostly blue, sometimes pink, purple, or white, the marginal ones enlarged; pappus 2–3 mm; 2n=24. Fields, roadsides, and waste places; native to the Mediterranean region, widely cult. and now a cosmopolitan weed.
cornflower, bachelor's button