Weed Seed: Sonchus arvensis (Perennial sow thistle)

Family

Asteraceae

Common Name

Perennial sow thistle

Regulation

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

Distribution

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

Perennial

Seed or fruit type

Achene

Identification features

Size

  • Achene length: 2.5 - 3.5 mm
  • Achene width:1.0 - 1.5 mm
  • Achene thickness: 0.5 - 1.0 mm

Shape

  • Long oval-shaped achene; flattened

Surface Texture

  • Achene has a dull surface with longitudinal folds and small transverse ridges

Colour

  • Achene is dark brown

Other Features

  • 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).

General Information

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).

Similar species

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.

Photos

Perennial sow-thistle (Sonchus arvensis) achenes
Perennial sow-thistle (Sonchus arvensis) achene
Perennial sow-thistle (Sonchus arvensis) achene, close-up of surface
Perennial sow-thistle (Sonchus arvensis) achene

Similar species

Similar species: Annual sow thistle (Sonchus oleraceus) achenes
Similar species: Annual sow thistle (Sonchus oleraceus) achene
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