Compilation
Senecio jacobaea

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Name

Identification
Senecio jacobaea L. [family ASTERACEAE ] (stored under name);
Related name
  • Senecio tremolsii
  • Senecio flosculosus
  • Senecio jacobaea
  • Senecio ambraceus
  • Senecio subalpinus
  • Senecio sp.
  • Jacobaea vulgaris
  • Senecio eversii
  • Senecio laciniosa
  • Senecio nemorosus
  • Senecio palustris
  • Senecio foliosus
Common name
  • Tansy ragwort, Flora of North America Vol. 20
  • stinking Willie, Flora of North America Vol. 20

Flora

Entry for Senecio jacobaea Linnaeus [family COMPOSITAE]
Herbarium
Flora of North America (FNA)
Collection
Flora of North America
Resource Type
Reference Sources
Entry From
Flora of North America, Vol 20,
Names
Senecio jacobaea Linnaeus [family COMPOSITAE], Sp. Pl., 2: 870. 1753
Jacobaea vulgaris Gaertner [family ]
Treatment Author(s)
Theodore M. Barkley†
Information
Perennials, 20–80(–100) cm (taprooted or branched caudices surmounting taproots). Herbage sparsely and unevenly tomentose, glabrescent except in leaf axils and among heads. Stems (often purplish-tinged) usually single, sometimes loosely clustered. Leaves ± evenly distributed (basal often withering before flowering); petiolate (sometimes obscurely); blades ovate to broadly ovate (usually 1–3-pinnate, lobes mostly obovate to spatulate), (4–)7–20(–30) × (1–)2–5(–12) cm, bases usually tapered, ultimate margins dentate (distal leaves similar, smaller). Heads (10–)20–60+ in corymbiform arrays. Calyculi of 2–6 (inconspicuous) bractlets (less than 2 mm). Phyllaries ± 13, 3–4(–5) mm, tips black or greenish. Ray florets ± 13; corolla laminae 8–12 mm. Cypselae all sparsely hairy or ray cypselae glabrous. 2n = 40.
Phenology
mar-may (spring), jun-aug (summer), sep-nov (fall)
Altitude range
0–1500 m;
Distribution
St. Pierre and MiquelonEurope.USA Calif.USA IdahoUSA Ill.USA MaineUSA Mass.USA Mich.USA Mont.USA N.J.USA N.Y.USA Oreg.USA Pa.USA Wash.Canada B.C.Canada N.B.Canada Nfld. and Labr. (Nfld.)Canada N.S.Canada Ont.Canada P.E.I.Canada Que.
Discussion
Senecio jacobaea is a weed introduced from Europe and now well established in places of cool, damp summers. It is toxic to livestock and legally noxious in most states and provinces where it occurs.
The Russian botanist E. Wiebe (2000) resuscitated Jacobaea for plants that are treated here as Senecio jacobaea, S. erucifolius, and S. cannabifolius. Phylogenetic studies may confirm the utility of recognizing Jacobaea as a distinct genus; to do so here would be premature.
Native/Introduced
introduced;

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