Weed Seed: Carduus acanthoides (Spiny plumeless thistle)

Family

Asteraceae

Common Name

Spiny plumeless thistle

Regulation

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

Distribution

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

Worldwide: Native to northern Africa, temperate Asia, and most of Europe. Introduced to North America, Argentina, Uruguay, New Zealand, and beyond its native range in Europe (USDA-ARS 2016Footnote 2). Occurs across the continental United States, with the exception of some southwestern and southeastern states (Kartesz 2011Footnote 3).

Duration of life cycle

Annual or biennial

Seed or fruit type

Achene

Identification features

Size

  • Achene length: 2.5 - 3.0 mm
  • Achene width : 1.5 mm

Shape

  • Achene is elongate, tapering at the base, compressed laterally; may have a small hump to one side of the collar

Surface Texture

  • Achene is smooth, with longitudinal lines and transverse wrinkles on the surface

Colour

  • Achene is cream-coloured to light brown, often has a pink tint
  • The collar at the top of the achene is often yellow

Other Features

  • The style peg at the top of achene is usually short and thick.
  • Immature achenes can have a filamentous white pappus 1.3 - 2.0 cm long.

Habitat and Crop Association

Cultivated fields, pastures, rangelands, roadsides and disturbed areas (Desrochers et al. 1988Footnote 4, Darbyshire 2003Footnote 5).

General Information

Spiny plumeless thistle was first recorded on the east coast of North America in the late 19th century, possibly arriving in ships' ballast (Desrochers et al. 1988Footnote 4). It may form dense stands on disturbed sites and invade native and restored grasslands (Ministry of Agriculture, Food, and Fisheries 2002Footnote 6).

Similar species

Nodding thistle (Carduus nutans)

  • Nodding thistle achenes are a similar size and brown colour, elongate shape with a thick top peg, and longitudinal and transverse lines on the surface.
  • Nodding thistle achenes have a yellow base and the achene surface is covered with a smooth, varnish-like coating.
  • Immature nodding thistle achenes may have a wrinkled surface similar to spiny plumeless thistle, but they will have a yellow base.

Photos

Figure 1 - Spiny plumeless thistle (Carduus acanthoides) achenes
Spiny plumeless thistle (Carduus acanthoides) achenes
Figure 2 - Spiny plumeless thistle (Carduus acanthoides) achene
Spiny plumeless thistle (Carduus acanthoides) achene
Figure 3 - Spiny plumeless thistle (Carduus acanthoides) achenes
Spiny plumeless thistle (Carduus acanthoides) achenes
Figure 4 - Spiny plumeless thistle (Carduus acanthoides) top of achene
Spiny plumeless thistle (Carduus acanthoides) top of achene
Figure 5 - Spiny plumeless thistle (Carduus acanthoides) bottom of achene
Spiny plumeless thistle (Carduus acanthoides) bottom of achene
Figure 6 - Spiny plumeless thistle (Carduus acanthoides) achene
Spiny plumeless thistle (Carduus acanthoides) achene

Similar species

Figure 7 - Similar species: Nodding thistle (Carduus nutans) achenes
Similar species: Nodding thistle (Carduus nutans) achenes
Figure 8 - Similar species: Nodding thistle (Carduus nutans) achene
Similar species: Nodding thistle (Carduus nutans) achene
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