Annuals, (10–)20–40(–60) cm (taprooted). Herbage densely fetid-viscid (hairs glandular). Stems single. Leaves evenly distributed; petiolate; blades obovate to oblong (pinnately dissected to pinnatifid), 2–7 × 1.5–4 cm, bases tapered or ± truncate, ultimate margins wavy or crenate-dentate (distal leaves sessile, smaller, ± clasping). Heads (1–)3–8(–30) in irregular, corymbiform arrays. Calyculi of 2–5 bractlets (largest to 4 mm). Phyllaries (± 13) ± 21, 5–7 mm, tips black. Ray florets ± 13; corolla laminae 1–2 mm (usually coiled, scarcely surpassing phyllaries). Cypselae usually glabrous, sometimes hairy. 2n = 40.

Flowering spring–fall. Disturbed sites, especially open sandy or gravelly places; 1–300 m; introduced; St. Pierre and Miquelon; Alta, B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que., Sask.; Conn., Ill., Maine, Mass., Minn., N.H., N.J., N.Y., Pa., R.I., Wis.; Eurasia.

Senecio viscosus is a smelly, Eurasian weed now widely scattered in areas of cool damp climates, often as a casual waif. The viscid hairs trap wind-blown particles of sand, dust, and soot, which give the surfaces varying textures and colors.