Plumeless Thistle - Carduus acanthoides

Above: Plumeless Thistle in Oak Savanna in Madison, Wisconsin (7/2/20).

Plumeless Thistle - Carduus acanthoides (Introduced - naturalized; ecologically invasive)

Plumeless Thistle is a biennial plant. Biennial means that it takes two seasons to complete their life cycle The first season they germinate and create a rosette. The second season they flower and produce seeds.

Plumeless Thistle is restricted in Wisconsin and is considered a ecological threat. It likes disturbed sites such as roadsides and ditch banks and will spread into fields and pastures. Plumeless Thistle can grow from 1'- 4' tall in it's second year.

Plumeless Thistle has pink/purple flower heads are usually about 1/2" - 1" wide.

Blooms July-October.

Above: Plumeless Thistle stem between sidewalk and curb on Tumalo Trail in Madison, Wisconsin (8/16/22). The stems are densely covered with leafy, spine-tipped “wings.”

Above: Plumeless Thistle leaf on shore of Lake Wingra in Vilas Park in Madison, Wisconsin (8/26/22). Leaves are deeply lobed and wavy around the edges with spines at the tips.

Other names: Spiny plumeless thistle, Welted thistle.

Etymology: Acanthoides – resembing a spine or thorn.

For more information on the Plumeless Thistle, visit Wikipedia.

Or, visit the UW-Madison Wisconsin Herbarium online virtual flora website page on Plumeless Thistle.

Or, download a pdf about Plumeless Thistle from the University of Wisconsin Extension's 2017 Weed Identification Series

Or, to eradicate, visit the Wisconsin DNR website on Plumeless Thistle.

Or, to compare it other Biennial thistles (Bull and Musk) download a Biennial Thistle Comparison pdf from the University of Wisconsin Extension's 2017 Weed Identification Series/Biennial Thistle Comparisons

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