Weed Seed: Carduus acanthoides (Spiny plumeless thistle)
Spiny plumeless thistle
Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.
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 length: 2.5 - 3.0 mm
- Achene width : 1.5 mm
- Achene is elongate, tapering at the base, compressed laterally; may have a small hump to one side of the collar
- Achene is smooth, with longitudinal lines and transverse wrinkles on the surface
- Achene is cream-coloured to light brown, often has a pink tint
- The collar at the top of the achene is often yellow
- 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).
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).
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.
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