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Ministry of Agriculture, Food and Rural Affairs

canada fleabane

Scientific Name: Conyza canadensis

Other names: horseweed, mare’s-tail and, vergerette du Canada

Family: Asteraceae or Compositae

General Description: Canada Fleabane is a winter or summer annual weed, reproducing only by seed.

Habitat: Canada fleabane occurs throughout Ontario in grain fields, pastures, waste places, roadsides, and gardens.


  • Seeds are 1-2 mm long, almost transparent
  • Seeds are carried for long distances by wind via their attached pappus (parachute)
  • Most seedlings emerge from late August through October and overwinter, others emerge from March to early May
  • Seedling plant begins as a basal rosette


  • Stems, erect
  • 10-180cm high
  • Hairy
  • little branched


  • Seedling leaves are soft, hairy and bright green
  • Older leaves are much harsher
  • Narrowly oval, rarely more than 1cm wide
  • Taper to a slender stalk
  • Sparsely hairy leaves with smooth or slightly toothed margins
  • Gradually decreasing in size from base to top of plant


  • Flowers are numerous on many short branches near the top of the main stem
  • Flower heads 3-5mm across
  • Ray florets are white but very short and usually concealed by the slightly longer involucral bracts around each flower head
  • Disk florets are yellowish and are light and fluffy at maturity
  • Flowers from July to late autumn.

Often Confused With / Distinguishing Features
Canada fleabane is easily distinguished by many narrow, bright green leaves and many small, yellow-green flower heads. The ray florets are inconspicuous and when mature, the flowers look light and fluffy. When parts of the weed are crushed they have a faint odour that is similar to the scent of carrots.

Herbicide Resistance
There are populations in Ontario that are resistant to:
1) glyphosate (WSSA group 9)
2) cloransulam (WSSA group 2)
3) glyphosate (WSSA group 9) and cloransulam (WSSA group 2)
4) paraquat (WSSA group 22)


Canada fleabane, hairy seedling leaves Canada fleabane, hairy seedling leaves Canada fleabane showing rosette of leaves Young Canada fleabane leafOld, mature leaf of Canada fleabaneWhole, mature plant of Canada fleabaneFlowers of the Canada fleabane weed

Click to enlarge.