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Native Wildflowers of the North Dakota Grasslands

JPG -- species photo

Wavyleaf Thistle (Cirsium undulatum)


A native plant of the Dakota prairies, wavyleaf thistle should not be confused with the noxious Canada thistle that infests our cropfields and gardens. Wavyleaf thistle is found on dry open soil from British Columbia to Texas and eastward to Michigan and Iowa, at elevations up to 9,500 ft.

This thistle has rose-purple flower heads that may be over two inches wide and an inch and a half tall. For floral beauty, these heads contrast nicely with the leaves and stems that are whitish gray because of a covering of wooly hairs. However, most people object to the sharp yellow spines that project from the intricately cut leaves and the sides of the flower heads. The thick perennial taproot of wavyleaf thistle penetrates deeply into the dry prairie soil. At maturity, the airborne seeds (achenes) with their feathery bristles are termed thistledown.

Wavyleaf thistle is avoided by livestock, but does not seem to increase in heavily grazed pastures, regardless of this obvious competitive advantage over more palatable plants. The thick roots of wavyleaf thistle were cooked for food by several tribes of native Americans. Thistledown is relished by birds for food and nest linings.

This plant is a member of the huge sunflower family (Asteraceae), in which the flowers are grouped into heads. Aster means "star" in Greek, in reference to the radiate arrangement of the flowers in the heads. The generic name is derived from the Greek cirsos, "a swollen vein," for which the early herbalists thought thistle a remedy. The specific name undulatum refers to the wavy leaf margins. Wavyleaf thistle was first described under a different genus by English naturalist Thomas Nuttall in the early 1800's. The species was later given its currently accepted name by the distinguished German botanist Curt Sprengel (1766-1833), professor of medicine at Halle.


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