NOXIOUS WEED
CO, NM, UT

Synonym: Breea arvense.  Cirsium arvense.  (Canada Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Meadows, disturbed areas.  Summer.
Near Yellow Jacket Canyon, August 3, 2005.

Canada Thistle spreads easily by both seed and root and it is, thus, 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 Breea 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, and the name which William Weber accepts, Breea arvense, was given in 1832.

"Arvense" is Latin for "of fields", and "Breea" honors William Thomas Bree, botanist and theologian.  (More biographical information.)

Synonym: Breea arvense.  Cirsium arvense.  (Canada Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Meadows, disturbed areas.  Summer.
Near Yellow Jacket Canyon, August 26, 2005.

The prickly basal rosette of leaves of Breea arvense.

Synonym: Breea arvense.  Cirsium arvense.  (Canada Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Meadows, disturbed areas.  Summer.
Near Yellow Jacket Canyon, August 3, 2005.

Synonym: Breea arvense.  Cirsium arvense.  (Canada Thistle)
Asteraceae (Sunflower Family)

Foothills, montane. Meadows, disturbed areas.  Summer.
Near Yellow Jacket Canyon, August 3, 2005.