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.
Seeds are light brown with a tuft of light brown hair to carry them off in the wind.
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?
on: 2011-07-09 00:45:24
Am pulling this out of my flowerbed often.
on: 2011-07-09 04:20:43
Me, too. :)
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.
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.
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!
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.
on: 2020-07-31 22:33:59
I've seen something like this on road verges. The plants I found have lanceolate leaves with a single prominent mid-vein, and several teeny-tiny leaves in each leaf axil. Flower buds are clustered in upper leaf axils, and appear even on plants as small as 6-7" tall. Is this the COnyza canadensis, or something else? We planted a wildflower seed packet and unfortunately my mother threw away the package. I didn't know if the above plant was from the packet, or the neighborhood (nothing else seems to have sprouted).
on: 2020-08-01 06:07:18
Ellen, your mystery plant is probably something else. Post a photo on the Minnesota Wildflowers Facebook page if you like.
on: 2020-08-01 11:27:09
You're right, K. Chayka. I fortuitously found some real horseweed in the garden today, and I can see the difference now.
on: 2020-09-30 18:35:10
Well, turns out they were all horseweeds in different stages of growth.
on: 2021-07-21 13:13:58
Am volunteering to assist city in recovering a bee, bird butterfly garden. Horsesweed is in it. Dopurpose? It out or does it serve a purpose?
on: 2021-07-21 14:41:40
Patty, I don't know that horseweed serves any special purpose that can't be done by other more desirable members of the aster family. It can be quite prolific and some even question its native status. I pull it out of my own garden whenever I see it. I wouldn't want it in a restoration, either.
on: 2021-08-05 18:40:57
We built a berm behind our house last summer to keep from flooding. We planted it with native plants. This year the berm was overtaken by Canada Horseweed before I understood what it was. Now, it is so hot and dry I do not want to disturb the soil more, so I am wondering if I could just cut it next to the ground and deal with it again next year. Hopefully, we get some rain soon.
on: 2021-08-05 19:04:51
Bonnie, if the plants have already flowered, decapitate the stems and throw the flowering/fruiting parts in the fire pit. Cutting the rest of the stems off at ground level now may prevent further seed production this year, but you still have a seed bank from previous years to contend with.