|
Cirsium arvense. Synonym: Breea arvense. (Canada
Thistle) Foothills, montane. Meadows,
disturbed areas. Summer. Canada Thistle spreads easily by both seed and root and it is, therefore, very difficult to exterminate. Cutting down this Thistle only brings up five times as many root sprouts as before. Herbicides or cutting off the above ground stem every few days are the only ways to remove this noxious weed -- and these two methods don't work very well either. Leaves of Cirsium arvense are very prickly, flower heads numerous and sweet smelling, and seed production is enormous. Flowers are unisexual and usually only male or female flowers occur on each plant. In 1753 Linnaeus named this species, a native of Eurasia, "Serratula arvensis", it was renamed "Cirsium arvense" (its most widely accepted name today) in 1772. Breea arvense, the name which William Weber accepts, was given in 1832. "Arvense" is Latin for "of fields", and "Breea" honors William Thomas Bree, botanist and theologian. (More biographical information.) |
|
|
Cirsium arvense. Synonym: Breea arvense. (Canada
Thistle) Foothills, montane.
Meadows,
disturbed areas. Summer. The leaves of Cirsium arvense are narrow, deeply notched, and armed with numerous spiny tips. It is common for basal rosettes of leaves to occur in clusters. |
|
|
Cirsium arvense. Synonym: Breea arvense. (Canada
Thistle) Foothills, montane.
Meadows,
disturbed areas. Summer. |
|
|
Cirsium arvense. Synonym: Breea arvense. (Canada
Thistle) Foothills, montane.
Meadows,
disturbed areas. Summer. |
Range map © John Kartesz,
County Color Key
|
Range map for Cirsium arvense |
Species present in state and native
Species present in state and exotic
Species not present in state
Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Eradicated
Questionable presence