Annuals, 20-100 cm. Stems usually 1, erect, ± openly branched distally, loosely tomentose. Leaves ± loosely gray-tomentose; basal leaf blades linear-lanceolate, 3-10 cm, margins entire or with remote linear lobes, apices acute; cauline linear, usually not much smaller except among heads, usually entire. Heads radiant, in open, rounded or ± flat-topped cymiform arrays, pedunculate. Involucres campanulate, 12-16 mm. Phyllaries: bodies green, ovate (outer) to oblong (inner), tomentose or becoming glabrous, margins and erect appendages white to dark brown or black, scarious, fringed with slender teeth ± 1 mm. Florets 25-35; corollas blue (white to purple), those of sterile florets raylike, enlarged, 20-25 mm, those of fertile florets 10-15 mm. Cypselae stramineous or pale blue, 4-5 mm, finely hairy; pappi of many unequal stiff bristles, 2-4 mm. 2n = 24 (Russia). Flowering spring-summer (May-Sep). Grasslands, woodlands, forests, roadsides, other disturbed sites; 50-2400 m; introduced; Greenland; Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.). N.S., Ont., P.E.I., Que., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; s Europe. Centaurea cyanus is a commonly cultivated garden ornamental. Its cypselae are often included in wildflower seed mixes and it naturalizes readily in many areas.
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 נ1 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.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.