Cirsium arvense
 
Canada Thistle

Male Flower

Moose Mountain Provincial Park
21-August-2009

Note there are female flower parts present.  However, they are sterile rendering the flower functionally staminate.

bullet

Arvense: Answers to key questions in Budd's Flora and Flora of Alberta leading to this species. 
bullet

perennial plants

bullet

plants from deep creeping rootstocks; NOT [plants without creeping rootstocks]

bullet

male and female flowers on separate plants; NOT [male and female florets on the same plant or flower head]

bullet

bracts of involucre only slightly, if at all, cobwebby, and if so the inner bracts twisted and not spine-tipped; NOT [bracts of involucre covered with cobwebby hairs, and all bracts spine-tipped]

bullet

heads small, less than 2.5 cm high; NOT [heads larger, more than 2.5 cm high]

bullet

involucres 1-2 cm high; NOT [involucres more than 2 cm high]

bullet

involucres rarely over 12 mm wide; NOT [involucres usually more than 12 mm wide]

 

bullet

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

juice watery; NOT [juice milky]

bullet

leaves with spiny margins

bullet

bracts of involucre not dry or parchmenty, usually green; NOT [bracts of involucre dry, parchmenty or membranous, not green]

bullet

some involucral bracts spiny-tipped

bullet

involucral bracts without hooked bristles

bullet

receptacle densely bristly; NOT [receptacle naked]

bullet

flower heads with all florets tubular

bullet

stamens united to form a tube around the pistil

bullet

pappus present, distinct; NOT [pappus none or inconspicuous]

bullet

pappus of capillary bristles; NOT [pappus of scales, or of awns, or a crown or none]

bullet

pappus bristles much longer than achene; NOT [pappus hairs not longer than achene]

bullet

pappus bristles plumose; NOT [pappus bristles naked or merely minutely barbellate]