Weed Seed: Jacobaea vulgaris (Tansy ragwort)



Common Name

Tansy ragwort


Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.


Canadian: Occurs in BC, MB, NB, NL, NS, ON, PE, QC (Brouillet et al. 2016Footnote 1).

Worldwide: Native to northern Africa, Europe and temperate Asia and introduced in North America, China, Australia, New Zealand, and beyond its native range in Europe (Finland, Norway, Russia) (USDA-ARS 2016Footnote 2). In the United States, it occurs mostly in the west and northeastern regions (Kartesz 2011Footnote 3).

Duration of life cycle

Short-lived perennial

Seed or fruit type


Identification features


  • Achene length: 1.3 - 2.5 mm
  • Achene width: 0.4 - 1.0 mm


  • Achene elongate; tapered at base and top is truncate

Surface Texture

  • Achene surface has a satin sheen with a roughened surface
  • Achene is ribbed, with short hairs in the grooves


  • Achene is light yellow to golden brown with white-haired furrows

Other Features

  • A long, white pappus sometimes present on immature achenes
  • Achenes are dimorphic; the uncommon outer fruits are hairless

Habitat and Crop Association

Pastures, hay fields, old fields, roadsides, railway lines and disturbed areas (Bain 1991Footnote 4, Darbyshire 2003Footnote 5). Not a known weed of crops, however a problem in pastures due to toxicity (Royer and Dickinson 1999Footnote 6).

General Information

Tansy ragwort is thought to have been introduced into Canada in the 1850s in ships' ballast (Bain 1991Footnote 4). Tansy ragwort contains alkaloids which are toxic to cattle, deer, horses and goats. A single plant can produce as many as 150,000 seeds, which can remain viable for over 20 years (Ministry of Agriculture, Food, and Fisheries 2002Footnote 7).

Similar species

Common groundsel (Senecio vulgaris)

  • Common groundsel has a similar size, cylindrical shape, longitudinal ribs and short surface hairs as tansy ragwort.
  • Common groundsel (length: 2.8 - 3.0 mm) is generally longer, a darker colour and the surface hairs are more dense than tansy ragwort.


Tansy ragwort (Jacobaea vulgaris) achenes
Tansy ragwort (Jacobaea vulgaris) achene
Tansy ragwort (Jacobaea vulgaris) achene
Tansy ragwort (Jacobaea vulgaris) achene, collar (top-down view)
Tansy ragwort (Jacobaea vulgaris) achene, collar (side view)

Similar species

Similar species: Common groundsel (Senecio vulgaris) achene
Similar species: Common groundsel (Senecio vulgaris) achenes
Similar species: Common groundsel (Senecio vulgaris) achene, close-up of surface
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