*Cirsium arvense (Linnaeus) Scopoli. Canada Thistle, Field Thistle. Phen: Jul-Nov. Hab: Pastures, disturbed areas. Dist: Native of Europe.

Origin/Endemic status: Europe

Taxonomy Comments: Two varieties are often recognized: var. arvense, with leaves shallowly undulate-lobed and with only a few fine marginal prickles, and var. horridum, with leaves strongly sinuate-pinnatifid and with numerous well-developed marginal prickles.

Synonymy: = Ar, FNA19, GrPl, K1, K3, K4, Mi, NE, NY, Pa, S, Tn, Va, W; = Breea arvense (L.) Less.; = Carduus arvensis (L.) Robson – RAB; > Cirsium arvense (L.) Scop. var. arvense – C, F, G, Il, Oh3, SE1; > Cirsium arvense (L.) Scop. var. horridum Wimm. & Gräbner – C, G, Il, Oh3, SE1; > Cirsium arvense (L.) Scop. var. integrifolium Wimm. & Graebn. – F; > Cirsium arvense (L.) Scop. var. mite Wimm. & Gräbner – F; > Cirsium arvense (L.) Scop. var. vestitum Wimm. & Graebn. – F

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