1. Cosmos bipinnatus Cav. (garden cosmos, Mexican aster)

Pl. 276 e; Map 1166

Stems 25–200 cm long, glabrous or sparsely pubescent with short, appressed-ascending hairs, rarely minutely roughened to the touch. Leaves sessile or with a short petiole to 10 mm long. Leaf blade 1–12 cm long, 1 or 2 times deeply pinnately divided, the ultimate segments narrowly linear, often threadlike, 0.5–1.5 mm wide. Involucre 6–15 mm long, 7–15 mm in diameter, the outer series of bracts 6–13 mm long, spreading to loosely ascending, linear to narrowly triangular or narrowly lanceolate, tapered to a sharply pointed tip, mostly with slender, white margins; the inner series of bracts 7–13 mm long, erect or strongly ascending, lanceolate to narrowly ovate, rounded or more commonly angled to a bluntly or sharply pointed tip, mostly with relatively broad, white margins. Ray florets with the corolla 1.5–4.0 cm long, most commonly pink, less commonly white or purplish pink. Disc florets with the corolla 5–7 mm long, yellow. Fruits 7–16 mm long (including the beak), the surface glabrous but often dotted with scattered impressed glands, smooth or appearing minutely pebbled. 2n=24. July–October.

Introduced, uncommon and sporadic (native of Arizona, Mexico; introduced widely in the U.S., Canada). Railroads, roadsides, and open, disturbed areas.