Conyza canadensis (Canadian Horseweed)

Plant Info
Also known as: Canada Fleabane
Genus:Conyza
Family:Asteraceae (Aster)
Life cycle:annual, biennial
Origin:native
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):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals Cluster type: panicle

[photo of flowers] 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: Leaf attachment: alternate Leaf type: simple

[photo of leaves] 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.

Fruit: Fruit type: seed with plume

[photo of fruit] Seeds are light brown with a tuft of light brown hair to carry them off in the wind.

Notes:

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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More photos

Photos by K. Chayka taken in Ramsey County. Other photos courtesy Peter M. Dziuk.

Comments

Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Robbi - St. Cloud
on: 2011-07-09 00:45:24

Am pulling this out of my flowerbed often.

Posted by: K. Chayka - New Brighton
on: 2011-07-09 04:20:43

Me, too. :)

Posted by: A. L. - St. Paul
on: 2012-05-15 20:54:29

I ordered a great amount of compost from a local nursery (very reputable)last May (2011). I put in a native and perennial garden in my front lawn, and then I put about 4 to 5 inches of this compost on every inch of the garden. Now i have Horseweed. I am pulling like mad! Am going back to the nursery this week to ask for my money back.

Posted by: K. Chayka
on: 2012-05-15 21:20:32

A.L., there are worse things than horseweed. At least it is a native "weed" and not really that difficult to control. I had a fair amount in my own garden and pulling it for just one season has pretty much eliminated it.

Posted by: Jane - Todd County - near the Long Prairie River
on: 2014-08-08 23:09:33

This weed is everywhere! It has taken over our horse pasture. Some advice has been to till it under and reseed (heavily). A few weeks ago we did mow the pasture - to cut the weeds - and allow the grass to make some progress. However, it is so dry right now - that the opposite has happened - weeds everywhere choking out the grass. This is a terrible weed to have around livestock/horses. We had planned to burn off the pasture this fall and heavily reseed. But wonder about tilling/reseeding now - even though it is so dry. Please reply if you have advice?? Thank you!

Posted by: Brenda Pittman - Faribault, Rice County
on: 2017-08-13 10:23:03

We have planted various wildflower seed packets and never knew what these plants were until this year. Not sure if we should give them as much space as the other native flowers growing in the space such as black eyed Susan's, purple coneflower, and iron weed.

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