Kansas Wildflowers and Grasses

HORSEWEED

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Conyza canadensis (L. ) Cronquist

Konza Prairie, Riley County, Kansas

Annual

Height: 3 inches to 10 feet, (often 1.5 to 5 feet)

Family: Asteraceae - Sunflower Family

Flowering Period: June, July, August, September

Also Called:

Mare's-tail, canada fleabane, canadian horseweed.

Stems:

Erect, solitary, unbranched below, occasionally branching above mid-point, coarsely hairy.

Leaves:

Alternate, numerous, sessile to short-stalked, simple, oblanceolate to linear, 4/5 to 4 inches long, 1/6 to 2/5 inch wide; margins entire or lower leaves with coarse teeth; stiff-hairy along margins and on mid-vein; tip pointed; basal leaves larger, sometimes falling early; stem leaves reduced upward.

Inflorescences:

Panicle, open, elongated, terminal; heads numerous, inconspicuous, bell-shaped, about 1/5 inch across; involucral bracts in 1-2 series, overlapping, lanceolate to linear, 1/10 to 1/6 inch long, greenish.

Flowers:

Ray florets 20-40, white or sometimes pale pink; disk florets 8-30, yellow.

Fruits:

Achene, egg-shaped to oblanceolate, around 1/25 inch long, flattened, tan to pale grayish-brown, tipped with 15-25 white to tan bristles 1/12 to 1/8 inch long, enclosing small seed.

Habitat:

Waste areas, prairies, fields, roadsides, gardens, stream banks, open disturbed sites.

Distribution:

Throughout Kansas

Origin:

Native

Reproduction:

By seed

Toxicity:

The leaves and flowers contain a chemical that is irritating to the skin and nostrils of horses. It has been reported toxic to sheep and cattle, but this has not been confirmed experimentally.

Uses:

Native Americans steeped the leaves and took the liquid for diarrhea and stomach pains and applied the cold infusion to snake bites and pimples. The crushed plant was rubbed on sunburns and sore joints and a poultice of the crushed plant was applied to earaches and to the temples for headaches.

Comments:

Horseweed is a common weed that can be quite variable in size. It has been known to flower when under 3 inches to as tall as 10 feet. It is one of the few North American weeds introduced to Europe, Africa and Asia. The foliage has a strong aroma.

Horseweed florets