102. Senecio L. (groundsel)

Plants annual. Stems erect or ascending, unbranched or few-branched, sometimes lined or angled, glabrous or with patches of fine, woolly (cobwebby) hairs, sometimes with scattered, minute hairs toward the tip. Leaves in a basal rosette and alternate, progressively reduced in size from the stem base to tip, cobwebby-hairy when young, often becoming glabrous or nearly so at maturity, sessile or the lowermost long-tapered to a poorly defined petiole, the bases strongly clasping the stem. Leaf blades sometimes pinnately lobed, the margins otherwise shallowly or irregularly toothed or wavy to nearly entire, the venation pinnate. Inflorescences terminal and axillary from the uppermost leaves, panicles consisting of loose clusters to less commonly solitary flowers at the branch tips, rounded to broadly rounded in profile. Heads discoid or radiate, short- to long-stalked, with numerous florets. Involucre cylindrical to slightly wedge-shaped, the bracts in 2 series, glabrous or nearly so, those of the inner series more or less flat dorsally, those of the outer series minute, ascending and usually incurved. Disc corollas bright yellow. Style branches with a stigmatic line along each inner margin. Fruits narrowly oblong to narrowly oblong-elliptic in outline, not flattened, 5–10-ribbed, minutely hairy to less commonly nearly glabrous, brown. About 1,300 species, nearly worldwide, but most diverse in the Old World.

The description above applies only to the two species present in Missouri. Even in the restricted sense, Senecio on a worldwide basis includes plants with a bewildering array of growth forms and morphologies. Note that the native Missouri species formerly classified in Senecio have been transferred to the genus Packera.