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Ministry of Agriculture, Food and Rural Affairs

Annual sow-thistle

Scientific Name: Annual sow-thistle, Sonchus oleraceus L.

Other Names: Laiteron potager, Common annual sow-thistle, laiteron lisse, laiteron commun.

Family: Composite or Aster Family (Compositae

General Description: Perennial, reproducing by seed and by spreading underground rhizomes.

Habitat: Annual sow-thistle occurs throughout Ontario in waste places, along fence lines, roadsides, around buildings and occasionally in gardens. 

Stems & Roots

  • The part of the leaf closer to the stem is very narrow.
  • The base of the leaf clasping the stem has 2 angular or pointed lobes.
  • All margins with small teeth and soft weak spines.  

Flowers & Fruit

  • Seed ridged lengthwise and each ridge has numerous small cross-wrinkles.

Often Confused With/Distinguishing Characteristics
Easily distinguished by having leaves which are deeply lobed with the terminal lobe being short, broad and rounded or triangular.


Annual sow-thistle Annual sow-thistle Annual sow-thistle flower Annual sow-thistle
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