European Marsh Thistle (Cirsium palustre)

Photo by Steve Garske, GLIFWC

Distribution map of European marsh thistle in Wisconsin

Map courtesy of the WI
State Herbarium

DESCRIPTION

This herbaceous biennial grows 4 to 5 feet tall, primarily in moist areas. Leaves in first-year rosettes are spiny, long, deeply lobed and hairy on the underside. On flowering plants, leaves are 6 to 8 inches long near the base and shorter toward the top. Flowering stems are erect, thick, sometimes reddish in color, branched at the top and bristling with spiny "wings" aligned with the stem. Clusters of spiny purple flower heads bloom in June and July and by late summer produce tiny seeds attached to feathery "thistle-down."

LOOK-ALIKES

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The native marsh thistle (Cirsium muticum) has non-spiny stems and flower heads. Other common invasive thistles include Canada thistle (Cirsium arvense) which has spiny leaves but non-spiny stems and flower heads, plus bull thistle (Cirsium vulgare) and plumeless thistle (Carduus acanthoides) which have sharply spined leaves, stems and flower heads.

HABITS & HABITAT

In Wisconsin, European marsh thistle occurs in localized populations, primarily in northern counties. It prefers moist, acidic soils and is found along roadsides and in wetlands, forest edges and fields. Like other thistles, its seeds are readily dispersed by wind.

CONTROL

Mechanical: Repeated mowing or selective cutting close to the ground can reduce an infestation within three or four years. The rosettes can be hand-pulled or dug. Flowering heads can be cut off while in the unopened bud stage. If cut during or after flowering, flower heads should be gathered and destroyed.
Chemical: Clopyralid or metsulfuron-methyl may be used as foliage sprays. 1 to 2% active ingredient solution of glyphosate can also be used during the stage when plants are 6 to 10 inches tall, during the bud to flowering stage, or when applied to rosettes in the fall. If plants are near open water, use only herbicides approved for such use.