Marsh Thistle (Cirsium palustre)

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Biennial plant growing to about 1.5 m. Usually un-branched except the upper portion , stems are winged and armed with spines that result from its decurrent leaf bases. Much of the plant is covered in long, sticky hairs. It has deep segmented, spine-tipped leaves that have prominent woody veins. They are linear-oblong in shape and have tufts of hairs on the lower surface. The lower leaves are 15-20 cm long. This plant usually has many purple flower heads borne on short peduncles that do not reach more than 1 cm in length.

Key Identifiers
  • Flowers grouped in compact clusters at end of branches
  • Stems distinctly spiny-winged
  • Spine-tipped leaves with woody veins
  • Absence of strong spiny-tips on the phyllaries (bracts at the base of the flower head)
Location in Canada
In Canada, C. palustre has been reported in British Columbia, Ontario, Quebec, Nova Scotia and Newfoundland. The likelihood of this plant being in Alberta is quite high along the BC border.


British Columbia Ministry of Agriculture

British Columbia Ministry of Agriculture
Similar species
  • Canada thistle (Cirsium arvense) Lacks the spiny “winged” stem.
  • Welted thistle (Carduus crispus) Flowers heads are in a loose cluster and leaves lack prominent woody veins.
  • Bull thistle (Cirsium vulgare) Distinguished from all other thistles by the covering of short, sharp prickles on the upper, dark green surface of the leaf blade, these prickles (apart from the obvious spines along the margins and tips of the lobes) make the surface very harsh to the touch. Branches usually bear only a single flower head.

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For more information about the content of this document, contact Chris Neeser.
This document is maintained by Shelley Barkley.
This information published to the web on April 11, 2012.
Last Reviewed/Revised on August 21, 2018.