- Cirsium Palustre
Marsh plume thistle (Cirsium palustre) is a biennial and considered regionally noxious under the BC Weed Control Act. The majority of sites are located in the central interior. Marsh plume thistle is actively contained and monitored at sites in coastal BC, near Revelstoke, and Vernon. Marsh Plume thistle is a noxious weed in the Bulkley-Nechako and Fraser-Ft. George Regional Districts.
Marsh plume thistle is distinguished from other thistles by its single, slender, un-branched stem with spiny wings. Purple flowers cluster at the end, with spiny, hairy leaves that have prominent woody veins on the underside. Plants grow up to 1.5 metres in height at maturity.
Preferring moist to wet, naturally open, or disturbed habitats, marsh plume thistle spreads through wind and water seed dispersal, as well as ingestion and deposit by birds. Plants replace native vegetation in open, undisturbed, natural areas including wet meadows, fields, and riparian areas; thereby reducing native species and threatening natural diversity. Additionally, they form dense clumps in cut blocks, competing for moisture and nutrients with tree seedlings planted for reforestation. Tall stems can lead to snow press, permanently damaging tree seedlings.