Native Range

Europe and western Asia

Appearance

Marsh thistle is an upright forb that typically grows as a biennial but can sometimes grow as a short-lived perennial. Plants grow up to 4 ft (1.2 m) tall on average from a fibrous root system. Stems are slender and have spiny wings along their entire length. Leaves are alternate, lance-shaped, lobed, have prominent spines along their margins, and hairy undersides. Flower heads appear in clusters at the ends of stems and branches. They have purplish florets and bracts, and the bracts are not very spiny. Seeds are cream-colored, streaked in brown, and are topped by a tuft of fine hairs.

Impact

Introduced thistles currently infest millions of acres across North America, primarily occurring in or along roadways, waterways, agricultural fields, rangelands, pastures, forests, and disturbed areas. They are responsible for millions of dollars of damage annually in reduced agricultural yields and lowered forage value in grazing systems. Introduced invasive thistles can also displace native vegetation, negatively impacting wildlife and threatening the delicate ecological balance within many habitats.

Reference

Randall, C.B., J.E. Andreas, and J. Milan. 2024. Introduced Thistles: History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2024-8- INTRODUCED THISTLES-P. https://bugwoodcloud.org/resource/files/29168.pdf

Resources

• Weed of the Week - USDA Forest Service

Selected Images

Maps

Invasive Listing Sources

• Alberta Weed Control Act
• New Hampshire Invasive Plant Species Watch List
• Pacific Northwest Exotic Pest Plant Council, 1998
• Wisconsin's Invasive species rule – NR 40

References