Annuals, (15-)30-80+ cm (taproots fibrous-rooted). Herbage puberulent (hairs abundant, curly). Stems single. Leaves evenly distributed; petiolate; blades obovate to oblong, 3-7(-12) × 1-3(-4) cm, usually 1-2-pinnate, bases tapered, ultimate margins dentate (distal leaves similar, clasping, bractlike). Heads 12-24 in corymbiform arrays. Calyculi 0 or of 1-5+ linear to filiform bractlets. Phyllaries ± 13 (± 21), 4-7+ mm, tips greenish or minutely black. Ray florets 0 or 1-8+; corolla laminae usually 1-2+ mm (barely surpassing phyllaries). Cypselae hairy (especially on angles). 2n = 40. Flowering late spring-summer (northern areas of cool, climate); winter (southern areas). Mildly disturbed woodlands, open, sandy sites; 100-300 m; introduced; B.C., N.B., Nfld. and Labr. (Nfld.), N.S., P.E.I., Que.; Calif., La., Mass., Mich., N.J., Ohio, Oreg., Pa., Wash., Wis.; Eurasia. Senecio sylvaticus is a Eurasian weed that favors cool, wet climates. It is well established in coastal areas of the Pacific Coast and in parts of Newfoundland and Quebec; elsewhere in the flora, it appears to be sporadic.
