Canadian horseweed

Prepared by Jennifer L. D’Appollonio, Assistant Scientist, University of Maine, Orono, ME 04469. Updated February 2018.

Scientific name: Conyza canadensis (L.) Cronquist; also Erigeron canadensis L.

Common name(s): Canadian horseweed, horseweed, Canadian fleabane, Canada fleabane, coltstail, marestail, butterweed

Links: USDA PLANTS Profile, Go Botany

Images: (to see enlargements [PC]: click on image, then right click and choose “view image”)



-native North American plant

-seeds can germinate late summer – early fall or in the spring

-produces lots of seeds

-inhabits a wide range of growing and cultivation conditions

  • drought and water logged conditions


-very herbicide resistant

-resistant to roundup

-can be managed by

  • thick mulch layer
  • hand pulling
  • continued mowing
  • post emergent herbicides


Boggs, Joe, and Joe. “THE WEEKLY WEED: Canadian Horseweed (Conyza Canadensis).” BYGL, 2016,