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