Skip to content.
Français

Some features of this website require Javascript to be enabled for best usibility. Please enable Javascript to run.

Ministry of Agriculture, Food and Rural Affairs

Perennial sow-thistle

Scientific Name: Sonchus arvensis

Other Names: laiteron des champs, creeping sow-thistle, field sow-thistle, glandular-hairy perennial sow-thistle

Family: Composite or Aster family (Compositae)

General Description: Perennial sow-thistle is a perennial weed reproducing by seed and by buds on underground roots.

Habitat : Perennial sow-thistle occurs throughout Ontario in cultivated fields, pastures, meadows, woodland, waste places, roadsides, gardens and occasionally in lawns.

Seedlings

  • Leaves are broadly club-shaped
  • Leaves have irregularly toothed margins with prickles at the end

Stems

  • Stems are erect
  • Reaching a height of 60-150 cm
  • Smooth and hairless on the lower part but glandular-hairy towards the top and on branches
  • Each hair has a tiny gland at its tip

Leaves

  • Leaves are alternate (1 per node)
  • Leaves are variable in shape
  • Lower leaves are lobed and irregularly toothed
  • Middle and upper leaves are similar but have shorter stalks and clasp the stem
  • Uppermost leaves are small and narrow, have no lobes and very few teeth

Flowers and Fruit

  • Flower heads are bright yellow and 2.5 – 4 cm in diameter
  • Each flower head has strap-shaped ray florets
  • Flowers from June to late autumn  

Often Confused With / Distinguishing Features
The perennial sow-thistle is often confused with several weeds. The hairs with glands on its tips do not occur in smooth perennial sow-thistle which is often confused with perennial sow-thistle. It is also commonly mistaken for annual sow-thistle, spiny annual sow-thistle and dandelion.

Herbicide Resistance
No documented cases of herbicide resistance to date.

References
http://www.weedinfo.ca/en/weed-index/view/id/SONAR
http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/perennial_sowthistle.htm

 

Perennial sow-thistle seedling at the 2-leaf stage Perennial sow-thistle leaf Perennial sow-thistle before flowering Perennial sow-thistle flower head Perennial sow-thistle plantClick to enlarge.