Weed Seed: Centaurea iberica (Iberian starthistle)
Invasive Plant - Iberian Starthistle (Centaurea iberica)
Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order, 2016 under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.
Listed on the List of Pests Regulated by Canada established under the Plant Protection Act.
Canadian: Absent from Canada (Brouillet et al. 2016Footnote 1).
Worldwide: Native to areas from eastern Europe to extreme western China and India. Introduced in the United States, where it has been found in the Pacific states, Wyoming and Kansas (CFIA 2012Footnote 2). Also introduced in Argentina and outside of its native range in Europe (CABI 2016Footnote 3).
Duration of Life Cycle
Biennial; may behave as an annual or short-lived perennial
Seed or Fruit Type
- Achene length: 3.0 - 4.3 mm
- Achene width: 1.5 - 2.0 mm
- Pappus length: 1.0 - 3.3 mm
- Oblong-shaped achene with rounded bottom and flat top, compressed; large notch near the base along the narrow edge
- Achene is smooth with satin sheen
- Achene is white and brown-streaked; variable in colouration
- White pappus is composed of flat bristles of variable lengths
- Outer bristles of pappus tend to be shortest, increasing in length towards the inside
Habitat and Crop Association
Fields, pastures, rangelands, woodlands, shrublands, banks of watercourses, roadsides and disturbed areas ( DiTomaso and Healy 2007Footnote 4, CABI 2016Footnote 3). In the United States, it is highly competitive along roadsides and in rangelands.
Iberian starthistle was accidently introduced into the western United States, from where it has since spread, most notably in the 1920s (DiTomaso and Healy 2007Footnote 4) and the 1950s (Graham and Johnson 2003Footnote 5).
Purple starthistle (Centaurea calcitrapa)
- The achenes of purple starthistle are a similar size, oblong shape and smooth surface with reddish-brown streaks that appear like wood-grain.
- The achenes of purple starthistle have a smaller basal notch, dull surface and lack a pappus compared to Iberian starthistle.
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