Weed Seed: Inula britannica (British yellowhead)

Family

Asteraceae

Common Name

British yellowhead

Regulation

Prohibited Noxious, Class 1 in the Canadian Weed Seeds Order, 2016, 2016 under the Seeds Act. All imported and domestic seed must be free of Prohibited Noxious weed seeds.

Distribution

Canadian: Occurs in ON and QC (Brouillet et al. 2016Footnote 1).

Worldwide: Native to Europe and temperate Asia. Introduced to Canada and the United States (NY, DC). May be an occasional escape rather than truly established in North America (eFloras 2016Footnote 2).

Duration of life cycle

Perennial

Seed or fruit type

Achene

Identification features

Size

  • Achene length: 1.0 - 1.5 mm
  • Achene width: 0.2 - 0.5 mm
  • Pappus length: 4.0 - 6.0 mm

Shape

  • Achene is oblong with flat ends

Surface Texture

  • Surface of achene has several longitudinal ribs, is rough and covered with thin white hairs

Colour

  • Achene is medium brown

Other Features

  • Pappus hairs are barbed, appear to be persistent.
  • Thin, distinctive ring of white tissue at the base of the achene.

Habitat and Crop Association

Wet places (e.g., streambanks, ditches, marshes, wet woods and grasslands), nurseries, roadsides and waste places (FNA 1993+Footnote 3, CABI 2016Footnote 4). Its roots and rhizomes are known to contaminate Hosta spp. root systems (CABI 2016Footnote 4).

General Information

Introductions of British yellowhead into Canada and the eastern United States started in approximately the 1920s and have mostly occurred through the nursery trade. Populations either did not persist or are small and contained (Lehtonen and Schall 2000Footnote 5).

In the Netherlands, where this species is known to be associated with Hosta spp., it has been subject to aggressive control since 2000 (Lehtonen and Schall 2000Footnote 5).

Similar species

Common groundsel (Senecio vulgaris)

  • Similar size, oblong shape, hairs on surface as British yellowhead.
  • The surface hairs of common groundsel are short and thick; the hairs of British yellowhead are longer and thin. Common groundsel does not have a white ring of tissue at the base of the achene.

Photos

Figure 1 - British yellowhead (Inula britannica) achene with pappus
British yellowhead (Inula britannica) achene with pappus
Figure 2 - British yellowhead (Inula britannica) achene with pappus
British yellowhead (Inula britannica) achene with pappus
Figure 3 - British yellowhead (Inula britannica) immature achenes
British yellowhead (Inula britannica) immature achenes
Figure 4 - British yellowhead (Inula britannica) base of achene
British yellowhead (Inula britannica) base of achene

Similar species

Figure 5 - Similar species: Common groundsel (Senecio vulgaris) achene
Similar species: Common groundsel (Senecio vulgaris) achene
Figure 6 - Similar species: Common groundsel (Senecio vulgaris) achenes
Similar species: Common groundsel (Senecio vulgaris) achenes
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