Scientific Name: Conyza canadensis

Common Name: horseweed

Other Common Names: houseweed, horseweed, fleabane, marestail, Canada fleabane, Canadian horseweed

Synonyms: Conyza canadensis var. canadensis; Erigeron canadensis; Leptilon canadense

Habit: Seedlings bear 2 to 3.5 mm long by 1-2 mm wide ovate hairless cotyledons. The spatula shaped first leaves are hairy on the upper side and at the leaf margin. Canada Fleabane reaches heights from 7.5 to 180 cm this highly branched plant is covered with short bristly hairs. The crushed plant is said to have a carrot-like scent. Canada fleabane has a fibrous root system.

Leaves: The alternate oblong or lance-shaped leaves are 2-10 cm long. The leaves are frequently bristly haired especially near the base and are short stalked. The leaves are smaller in size toward the top of the plant. These smaller leaves can be as large as 8 cm long and 1 cm wide they are stalkless with smooth margins.

Identifying Characteristics: Flowers white to yellow 3-5 mm across, Stems with numerous branches, carrot odor to crushed leaves and stem. Leaves contain herpene an irritant to the nostrils of horses. May cause skin irritations in some people. This plant is also an alternate host to several plant pathogens i.e. aster yellows, tobacco mosaic virus, and tobacco ring spot virus.

Flower Seed Head: White ray and yellow disk florets compose the numerous flower heads measuring 3-5 mm across. The ray florets are usually hidden by the floral bracts. The numerous flower heads are crowded in to terminal clusters.

Seed Fruit: The fruit an achene bears an oblong, yellowish-brown, and flattened seed that is usually less than 2 mm long. The pappus is white to tan in color. Plants are capable of producing 10,000 seeds

Where Found: Throughout Canada and the United States in cultivated crops, pastures, and meadows.

  • Life cycle: biennial

  • Milky sap: Not Present

  • Plant type: Herb

  • Thorns: Not Present

  • Plant family: Asteraceae

  • Leaf arrangement: alternate

  • Ochrea: Not Present

  • Leaf margin: serrated

  • Stem hairs: has hairs

  • Flower color: white; yellow; pink

  • Growth habit: upright and nonwoody

  • Stem: round or oval

  • Leaf structure: simple

  • Leaf hairs: has hairs

  • Flower diameter: pencil; dime

  • Flower symmetry: radial symetery

  • Root structure: fibrous; taproot

  • Leaf stalk: none