Canada ThistleCirsium arvense
- Moss, Flora of Alberta – Common
- Global Invasive Species Database – Yes
- NatureServe Rank – High
- Haber, Upland – Moderate
- Haber, Wetland – No
- CWF, Status & Invasive Range – High, BC, SK, AB, MB, ON, QC, NF, NS, NB and southwestern US
- Alberta Revegetation Guidelines – No
- The Nature Conservancy – Yes, w/ ESA
- CBCN – Low
- AB Weed – Noxious
Spreads more vegetatively than by seed (the seed mostly falls not far from the parent, although the detached pappus spreads far and wide). Small root fragments can establish new plants, so that cultivation or pulling risk increasing the problem. Alleopathic. Unaffected or even encouraged by fire. Intolerant of fully saturated soil, but does well in moist margins as well as drier sites.
 Link to Bugwood Invasipedia for extensive information on biology, ecology, and management of this species.
As carbon dioxide in the atmosphere increases, all plants benefit. However, in growth chamber experiments, C. arvense gains biomass to a greater extent as concentration increases than do the native plants with which it competes.
Edible: see our recipe for thistle soup: . Peeled, the stems can be cooked and taste somewhat like Artichoke. Young leaves, de-prickled, can also be eaten. The flowers can be used to curdle milk.
Alberta Invasive Plants Council factsheet: 
US National Park Service fact sheet: 
E.W. Bork, C.W. Grekul, and S.L. DeBruijn, "Management of Canada Thistle in Pasture", University of Alberta, 2005 
Szczawinski & Turner, Edible Garden Weeds of Canada, ISBN 0-88902-752-8