Marsh Thistle

Photo Credit: Daniel Laubhann

Common Name: Marsh Thistle

Scientific Name: Cirsium palustre

Habitat: grassland, grassland wet, forests - wet areas, ditches

Provincial Designation: Prohibited Noxious

Prohibited Noxious weeds are plant species designated in the Alberta Weed Control Act. Prohibited noxious weeds must be destroyed when found, meaning all growing parts need to be killed or the plant's reproductive mechanisms need to be rendered non-viable.

Origin

Marsh thistle is native to Europe. The method of its introduction into North America is unknown. It was first collected in the U.S. in 1902 and Newfoundland in 1910.

Legislated Because

It is unpalatable and replaces desirable forage plants. It can invade undisturbed riparian habitats, moist fields, and meadows. It replaces native vegetation, leading to a reduction in forage for wildlife and livestock.

Description

Several 1-2 cm wide flowers appear clustered at the end of the stem. The flowers are typically purple and occasionally white.

The leaves are typically spiny and deeply lobed.

A key characteristic of this plant is the prickly wings that grow along its stem.

This thistle usually grows in moist areas and reaches up to 2 m tall.

Can Be Confused With

Native Thistles - Cirsium species - When in doubt, please report suspicious thistles to to invasiveweeds@edmonton.ca
Canada Thistle - Cirsium arvense - but who cares - they’re both noxious weeds!