Carduus: Answers to key questions in Budd's Flora and Flora of Alberta leading to this genus. 

	juice watery; NOT [juice milky]
	leaves not mottled
	leaves with spiny margins
	receptacle densely bristly; NOT [receptacle naked]
	bracts of involucre not dry or parchmenty, usually green; NOT [bracts of involucre dry, parchmenty or membranous, not green]
	some involucral bracts spiny-tipped; NOT [involucral bracts with hooked bristles]
	flower heads with all florets tubular
	stamens united to form a tube around the pistil
	achenes 3-4 mm long; NOT [achenes 6-7 mm long]
	pappus present, distinct; NOT [pappus none or inconspicuous]
	pappus of hairs; NOT [pappus of scales, or of awns, or a crown]
	pappus hairs much longer than achene; NOT [pappus hairs not longer than achene]
	pappus hairs naked or merely minutely barbellate; NOT [pappus hairs plumose]