Flowers in Israel: Canadian Horseweed

Conyza canadensis, Erigeron canadensis,
Canadian Horseweed, Canadian Fleabane, Hebrew: קייצת קנדית, Arabic: شيخ الربيع

Scientific name:   Conyza canadensis (L.) Cronquist
Synonym name:   Erigeron canadensis L.
Common name:   Canadian Horseweed, Canadian Fleabane
Hebrew name:   קייצת קנדית
Arabic name:   شيخ الربيع
Plant Family:   Compositae / Asteraceae, מורכבים


Life form:   Annual
Stems:   Erect, main stem branches only in the upper half; lateral stems shorter than the central stem
Leaves:   Alternate, entire, glabrous to densely covered with short stiff hairs
Flowers:   Whitish flower heads that consist of 7-13 disk flowers surrounde by 20-40 ray flowers with ligules; phyllary midveins brown, conspicuously filled with raisin, glabrous to hairy
Fruits / pods:   Achenes; pappus bristles mostly 2.5-3mm long, dirty white
Flowering Period:   June, July, August, September
Habitat:   Cultivated areas (weeds), Disturbed habitats
Distribution:   The Mediterranean Woodlands and Shrublands, Semi-steppe shrublands, Shrub-steppes, Deserts and extreme deserts, Montane vegetation of Mt. Hermon
Chorotype:   American
Summer shedding:   Ephemeral


Derivation of the botanical name:

Conyza, konops (Greek), “a gnat”, and used by Pliny as a name for some kind of a fleabane, or konis (Greek), “dust”, its powder being used to kill fleas.

canadensis, referring to Canada.
Erigeron, Greek, er, spring; geron, an old man; suggested by the hoariness of some vernal species.

  • The standard author abbreviation L. is used to indicate Carl Linnaeus (1707 – 1778), a Swedish botanist, physician, and zoologist, the father of modern taxonomy.
  • The standard author abbreviation Cronquist is used to indicate Arthur John Cronquist (1919 – 1992), a North American botanist and a specialist on Compositae.

This is the only Conyza species with white-yellow ligulate florets.