1. Centaurea americana Nutt. (American basket flower)

Plectocephalus americanus D. Don

Pl. 251 a–c; Map 1040

Plants annual, with a taproot, moderately roughened, sometimes smooth toward the stem base, not appearing pale or whitened at maturity. Stems 20–100 cm long, erect or ascending, unbranched or with few ascending branches above the midpoint, somewhat angled or ridged, but not winged. Leaves 3–12 cm long, often dotted with minute, yellow to brown resin glands; basal and lower stem leaves with the blades mostly 15–35 mm wide, narrowly ovate to elliptic-obovate, angled or tapered to a sharply pointed tip, mostly sessile, entire or with few fine teeth; median and upper stem leaves gradually reduced, sessile, the base not decurrent (the elevated midvein usually running into the narrow ridges), median and upper stem leaves somewhat reduced, entire, lanceolate to narrowly lanceolate. Heads solitary at the stem tip or branch tips. Involucre 25–45 mm long, wider than long, broadly bell-shaped. Involucral bracts with the body narrowly to broadly elliptic, the margins entire, the outer surface glabrous or cobwebby-hairy, partially concealed by the appendages, the outer surface with several fine, parallel veins or grooves; the apical appendage well differentiated and appearing jointed to the body, ascending, lanceolate to narrowly lanceolate, mostly narrower than the main body, somewhat overlapping, straw-colored to reddish brown, the involucre with at least some green coloration easily visible, the margins comblike with a fringe of usually stiff, spreading or loosely upward-curved, parallel bristles. Florets discoid, but the marginal florets raylike. Pappus of many unequal bristles, these 8–14 mm long, white, sometimes shed by fruiting. Corollas of discoid florets 14–20 mm long, white or cream-colored, less commonly light pinkish purple, those of raylike florets 20–25 mm long, light pinkish purple to reddish purple or rarely white. Fruits 4–5 mm long, somewhat flattened, the attachment scar appearing lateral or strongly oblique, the surface grayish brown to black with faint, lighter stripes, glabrous or sparsely hairy. 2n=26. June–July.

Uncommon in the southwestern portion of the Ozark Division; introduced sporadically elsewhere in the state (Missouri to Louisiana west to Kansas and Arizona; introduced sporadically farther north and east). Glades and openings of mesic to dry upland forests; rarely banks of rivers; also pastures, railroads, and roadsides.

This showy native wildflower occasionally is cultivated as a garden ornamental.