2. Centaurea cyanus L. (cornflower, bachelor’s button, blue bottle)
Pl. 252 d, e;
Map 1041
Plants annual,
with a taproot, pubescent with dense, woolly hairs when young (appearing pale
or whitened), the pubescence often partially reduced to woolly or cobwebby tufts
at maturity, at least the leaf undersurface remaining persistently woolly.
Stems 20–120 cm long, erect or ascending, with ascending branches at or above
the midpoint, angled and/or ridged but usually not winged. Leaves 4–13 cm long;
basal and lower stem leaves with the blades mostly 2–5(–9) mm wide, linear or
narrowly lanceolate, tapered to a sharply pointed tip, tapered gradually to a
sessile or short-petiolate base, the margins entire or the basal leaves rarely
with a few linear lobes (the leaves then wider); median and upper stem leaves
somewhat reduced, mostly sessile, the base sometimes narrowly decurrent, the
blades linear, entire. Heads solitary at the branch tips. Involucre 11–16 mm
long, longer than wide (sometimes about as long as wide when pressed), more or
less bell-shaped. Lower and median involucral bracts with the body ovate, the
margins entire, the outer surface glabrous or finely woolly, not concealed by
the appendages; the apical appendage not strongly differentiated, ascending,
the broad, white or brownish- to purplish-tinged margins papery and with
coarse, ascending, triangular teeth. Upper involucral bracts similar but
oblong-lanceolate. Florets discoid, but the marginal florets raylike. Pappus of
many unequal bristles, these 2–4 mm long, straw-colored to brown, usually
persistent at fruiting. Corollas of discoid florets 10–15 mm long, those of
raylike florets 20–25 mm long, blue or less commonly purple, pink, or white.
Fruits 3.5–5.0 mm long, somewhat flattened, the attachment scar appearing
lateral, the surface grayish brown to yellowish brown, brown or nearly black,
with sometimes faint, lighter stripes, finely hairy. 2n=24. May–September.
Introduced,
widely scattered in Missouri (native of Europe, Asia; introduced throughout the
U.S. and Canada). Banks of rivers and ledges of bluffs; also fallow fields,
railroads, roadsides, and open, disturbed areas.
Centaurea
cyanus is a popular
garden annual and a component of some wildflower seed mixes. Steyermark (1963)
knew it from only ten widely scattered counties but suggested that it actually
was present in most counties. Surprisingly, since that time, it has been
collected in only a few additional counties.