Senecio vulgaris L.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Annual 1–4 dm from a ± evident taproot, leafy throughout, sparsely crisp-hairy or subglabrous; lvs coarsely and irregularly toothed to more often pinnatifid, 2–10 × 0.5–4.5 cm, the lower tapering to the petiole or petiolar base, the upper sessile and clasping; heads several or many, discoid, the fls all tubular and perfect; disk 5–10 mm wide; invol 5–8 mm, with ca 21 principal bracts and some short but well developed, black-tipped bracteoles; pappus very copious, from a little shorter than to equaling or generally surpassing the cors; achenes short-hairy chiefly along the angles; 2n=40. A weed in disturbed soil and waste places; native of the Old World, now widely distributed in n. temp. regions, and throughout our range. May–Oct.