Weed Seed: Sonchus arvensis (Perennial sow thistle)
Perennial sow thistle
Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.
Canadian: Occurs in all provinces and territories (Brouillet et al. 2016Footnote 1).
Worldwide: Native to Europe and temperate Asia, as far as the Russian Far East. Introduced in North America, Argentina, Chile, Australia, New Zealand, Japan, Indonesia and the Philippines (USDA-ARS 2016Footnote 2). In the United States it occurs throughout except for a few southern states (Kartesz 2011Footnote 3).
Duration of life cycle
Seed or fruit type
- Achene length: 2.5 - 3.5 mm
- Achene width:1.0 - 1.5 mm
- Achene thickness: 0.5 - 1.0 mm
- Long oval-shaped achene; flattened
- Achene has a dull surface with longitudinal folds and small transverse ridges
- Achene is dark brown
- Pappus of fine white filaments 2-3 times as long as the achene may be present
Habitat and Crop Association
Cultivated fields, pastures, meadows, lawns, gardens, fences, shores, ditches, thickets, forests, roadsides and disturbed areas (Lemna and Messersmith 1990Footnote 4, Darbyshire 2003Footnote 5). A weed of any annual crop in temperate areas, notably cereals, corn, oilseed crops, sugarbeet, potatoes and vegetables (CABI 2016Footnote 6).
Perennial sow thistle was probably introduced into North America as a seed contaminant (Lemna and Messersmith 1990Footnote 4).
A single plant may produce 3000-9750 seeds (Lemna and Messersmith 1990Footnote 4), which can remain viable in the soil for several years (CABI 2016Footnote 6).
Annual sow thistle (Sonchus oleraceus)
- Annual sow thistle achenes are similar in size, oval shape, being compressed and having longitudinal ridges as perennial sow thistle.
- Annual sow thistle achenes are narrower at the base, a lighter colour with variable transverse wrinkling as perennial sow thistle.
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