Cirsium arvense
Canada Thistle
Female Flower Head Bottom
Moose Mountain Provincial Park
21-August-2009
Note the outer flowers hide a smaller portion of the involucre than the outer flowers of the male heads do.
Arvense: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.
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Cirsium: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus.
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