Douglas Provincial Park
Note the yellow apical band. For C. undulatum the apical band is much narrower if it exists at all. Note also that the achene (minus the pappus) is less than 5 mm long. The achene of C. undulatum is more than 5 mm long. Finally, note that the pappus hairs (bristles) are plumose (having fine hairs on each side like a comb).
Budd's Flora requires that this plant not possess creeping rootstocks. Yet Flora of Alberta states the plant sometimes spreads by slender creeping roots. This is not inconsistent; a rootstock is not a root but rather an underground stem or rhizome.
Flodmanii: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species.
Cirsium: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus.