Senecio glabellus Poir.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Fibrous-rooted, mostly single-stemmed annual or winter- annual 1.5–8 dm, glabrous or obscurely floccose-tomentose in the axils; lvs mostly once pinnatifid (or in part twice pinnatifid) with generally rounded teeth and lobes, or the basal sometimes merely round- toothed, the largest ones at or near the base of the stem, to 20 × 7 cm, progressively reduced upward; heads ± numerous, the disk 5–10 mm wide; invol 4–6 mm, its bracts ca 21 or 13; rays 5–12 mm; achenes minutely hairy or glabrous; 2n=46. Moist, open or shaded places, often a weed in low fields; N.C. and Ky. to Fla., w. to S.D. and Tex., and adventive n. to s. Ont. May–July.