Cirsium arvense (Canada Thistle)
| Also known as: | Field Thistle |
|---|---|
| Genus: | Cirsium |
| Family: | Asteraceae (Aster) |
| Life cycle: | perennial |
| Origin: | Europe |
| Status: |
|
| Habitat: | sun; old fields, along roads, waste areas, wetlands, lakeshores |
| Bloom season: | June - October |
| Plant height: | 3 to 5 feet |
| Wetland Indicator Status: | GP: FACU MW: FACU NCNE: FACU |
| MN county distribution (click map to enlarge): |  |
| National distribution (click map to enlarge): |  |
Pick an image for a larger view. See the glossary for icon descriptions.
Detailed Information
Flower: 
![[photo of flowers]](/udata/r9ndp23q/purple/canada-thistle-100_9303.jpg)
Flower heads are ¾ inch across, lavender to pale pink or sometimes white. The bracts are flat, except for the tip which peels back away from the flower head. The bract tips are pointed but not spined, and typically a purplish color, sometimes the entire bract is tinged purple. One plant typically has numerous flower heads, single or in small clusters at the ends of branching stems.
Leaves and stem:
![[photo of leaves]](/udata/r9ndp23q/purple/canada-thistle-100_9058.jpg)
Leaves are stalkless, up to 6 inches long with yellow spines scattered along the wavy edges. The lower leaves are up to 2½ inches across and deeply lobed, with a spine at the tip of each lobe. The upper leaves are more narrow, and generally more toothed than lobed. Leaves may be somewhat hairy on the underside. The stem is light green, slightly ridged and may have scattered hairs but is not usually spiny.
Fruit:
![[photo of fruit]](/udata/r9ndp23q/pd/cirsium-arvense-2.jpg)
Fruit is a brown seed with a tuft of long white hairs to carry it off in the wind, spreading itself far and wide.
Notes:
Canada Thistle is highly aggressive, can form large, dense colonies from its creeping roots, and crowds out native plants pretty much everywhere it grows. It is fairly easy to identify from the numerous small lavender to pinkish flower heads, and bracts that have no spines. While it prefers moist conditions it can sprout up and persist just about anywhere. It is currently designated as a Prohibited-Control noxious weed in Minnesota, but the MN Weed Advisory group is recommending a change to Restricted noxious weed, due to "lack of a viable statewide control method". Unfortunately, the lack of a statewide program applies to pretty much all invasive species in Minnesota at this time and they are in essence giving up the pretense they can do anything to stop its spread. We can only hope that will change someday.
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More photos
budding Canada Thistle plant
an infestation of Canada Thistle
Canada Thistle with Crown Vetch
first year emerging leaves
spring rosette
Canada Thistle invading a landscape planting
unusual white flowers
budding Canada Thistle plant
an infestation of Canada Thistle
Canada Thistle with Crown Vetch
first year emerging leaves
spring rosette
Canada Thistle invading a landscape planting
unusual white flowersPhotos by K. Chayka and Peter M. Dziuk taken at various locations across Minnesota.
Comments
Have you seen this plant in Minnesota, or have any other comments about it?
on: 2010-03-20 18:50:26
Once again Canada gets the blame, first it's our weather and now the weeds. Actually, Canada thistle is not native to Canada at all, and actually came across to canada with the first Eurpean settlers. It is native to Europe and Africa, therefore an invasive species.
on: 2010-03-20 21:38:14
Don't get down about it... It's only called Canada thistle because it invaded Canada first!
on: 2012-07-03 20:52:32
Spotted this today around the water in the park
on: 2022-06-05 10:33:00
This began showing up on my property sporadically for the past 8 years but then exploded this year after clearing a large number of boxelders from my yard. need heavy gloves and both hands to pull it from the root.
on: 2023-06-25 08:45:07
Had several bunches of these flowers, there pretty to look at got some great photos
on: 2023-06-25 09:33:38
Jerold, I think Canada thistle is pretty ugly once it goes to seed. It also produces a massive network of rhizomes that can crowd out other, more desirable plants, which increases its ugliness to me. As the saying goes, beauty is in the eye of the beholder.
on: 2023-07-19 08:12:39
Sadly, this is everywhere in my area. It's also sad that our cultural norm is shifting to where people think this is a normal part of the landscape (along with other invasives like spotted knapweed and tansy). I continue to photo the State "prohibited" species and submit to EDDMapS, though realistically, nothing is going to happen.
on: 2023-07-22 01:55:52
This plant is just absolutely taking over around the NW side of Lake of the Isles. I went back this summer to check out all the swamp milkweed and blue vervain I saw last year, but the majority of what I saw was a field of creeping thistles in seed. In late July while driving I see creeping thistles in seed next to so many lakes and rivers. What a terrible plant outside its native range
on: 2024-07-04 22:50:45
I spotted several colonies in the prairie area of Tamarack Nature Center.
on: 2024-09-12 13:09:18
This thistle volunteered in Spring near a roof dripline on the E side of a building--among some beakgrain I'd planted there. Precise location is under the "pre-1975 record" dot at the far east edge of Hennepin County in the above MN distribution map. I let it grow until now, not certain of its ID. Its mature leaves are about 8" long and 3" wide--a bit larger than the 6" long and 2.5" wide mentioned above. iNaturalist says it's Canada Thistle. As of now, about 4 months after initially spotting it, the horizontal root system has spread out around 4' total--with 8 new plants emerged within that 4' circumference. Easy to see how this thistle could totally take over an area. Wow.