Canada Thistle

(Cirsium arvense)

 

Color Photographs: Copyright Nearctica.com, Inc.

Line Drawing: Britton, N.L., and A. Brown. 1913. An Illustrated Flora of the Northern United States and Canada, Second Edition.

 

Canada Thistle (Cirsium arvense)

Alien: Native of Europe.

Identification: Plant much branched. Flower head small (0.5 to 0.75 inches in diameter) arranged in clusters near the apex of the plant. Flower head round to ovoid topped with a cluster of lilac florets. Flower head bracts closely appressed, sometimes tinted with violet. Stem smooth, without spines or spiny plates. Leaves heavily incised with spines arming each of the lobes. Plant 1 to 5 feet in height.

Distribution: Throughout North America except for the southeastern United States.

Habitat: Canada Thistle is a weed of disturbed areas including pastures, fields, empty lots, and roadsides.

Flowering period: July to September.

Note: Canada Thistle is a misnomer because the species is an import from Europe.

Canada Thistle (Cirsium arvense)

Similar Species:

The small, multiple, nearly smooth flower heads are a distinctive feature of Canada Thistle.

Similar Species

No Similar Species