Weed Seed: Senecio inaequidens (South African ragwort)

Invasive Plant - South African Ragwort (Senecio inaequidens)

Family

Asteraceae

Common name

South African ragwort

Regulation

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.

Distribution

Canadian: Absent from Canada (Brouillet et al. 2016Footnote 1).

Worldwide: Native to southern Africa and introduced to many European countries and Taiwan (CFIA 2014Footnote 2). Reports from Mexico and parts of South America may refer to Senecio madagascariensis (CFIA 2012Footnote 3).

Duration of life cycle

Perennial

Seed or fruit type

Achene

Identification features

Size

  • Achene length: 2.0 - 3.0 mm
  • Achene width: 0.2 - 0.5 mm

Shape

  • Oblong-shaped achene with a narrow top

Surface texture

  • Achene has several longitudinal ribs; surface is roughened, appears sparkling under lights

Colour

  • Achene usually dark brown, may be light brown or green in immature specimens

Other features

  • Achene surface between the ribs is densely covered with worm-like white hairs
  • Immature achenes have a long, white pappus 2-3 times the length of the achene

Habitat and crop association

Colonizes a wide range of open ruderal habitats, as well as stream banks, coastal dunes, grasslands, vineyards and pastures (CFIA 2012Footnote 3).

General information

Historic introduction sites of South African ragwort in Europe were closely tied with the wool industry (CABI 2016Footnote 4). Pastures that contain South African ragwort produce lower quality forage due to the poisonous alkaloids in the plant (Dimande et al. 2007Footnote 5).

This species produces thousands of seeds per year that can be carried by water, hay, humans or machinery into new habitats (CABI 2016Footnote 4, Heger and Böhmer 2006Footnote 6).

Similar species

Common groundsel (Senecio vulgaris)

  • Similar size, oblong shape, and surface hairs.
  • Common groundsel tends to be sharply narrowed at both ends; South African ragwort is narrowed at one end. The surface hairs of common groundsel are short and sparse; the hairs of South African ragwort are longer and more dense.

Madagascar ragwort (Senecio madagascariensis)

  • Similar oblong shape, rough texture, surface hairs, and is closely related to South African ragwort.
  • Madagascar ragwort achenes are generally shorter than South African ragwort (2.0 - 2.5 mm long), both ends of achenes narrowed, usually red brown with short white hairs on the ribs.

Photos

South African ragwort (Senecio inaequidens) achenes
South African ragwort (Senecio inaequidens) achene
South African ragwort (Senecio inaequidens) achene, close-up of surface
South African ragwort (Senecio inaequidens) achene, top down view

Similar species

Similar species: Common groundsel (Senecio vulgaris) achenes
Similar species: Common groundsel (Senecio vulgaris) achene
Similar species: Madagascar ragwort (Senecio madagascariensis) achene
Similar species: Madagascar ragwort (Senecio madagascariensis) achenes
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