Conyza canadensis (Canadian Horseweed)
|Also known as:||Canada Fleabane|
|Life cycle:||annual, biennial|
|Habitat:||sun; fields, prairies, roadsides, railroads, gravel pits, vacant lots, yards, disturbed soil|
|Bloom season:||July - October|
|Plant height:||6 inches to 7 feet|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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A large branching cluster of stalked flowers at the top of the plant. Individual flowers are about 1/8 inch across with 20 to 40 minute white or pinkish rays (petals) and a yellow center disk. The flowers aren't very noticeable until you get relatively close to the plant, and look like they are just starting to open up even when in full bloom. Bracts are narrow and smooth to sparsely hairy.
Leaves and stem:
Leaves are narrow, to 4 inches long and less than ½ inch wide, becoming progressively smaller as they ascend the stem. The leaf edges are covered in stiff hairs, on the lower part of the plant have small widely spaced teeth, those on the upper plant are toothless. There is little or no stalk. Leaves are alternately attached and crowded along the stem. Stems are mostly unbranched except near the flowers, stout, covered in stiff hairs, and mostly erect, though may fall over from the weight of the flowers.
Canadian Horseweed is a common weedy plant that grows almost anywhere. It seems to prefer dry, disturbed soil, but will grow in moist habitats as well. In the harshest conditions it may be small and spindly but can become quite tall and robust in favorable habitat.
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Photos by K. Chayka taken in Ramsey County. Other photos courtesy Peter M. Dziuk.
Have you seen this plant in Minnesota, or have any other comments about it?