Wavy-leaf Thistle: Cirsium undulatum Synonym: Cirsium undulatum var. undulatum)

Wavy-leaf thistle is a stout, single-stemmed short-lived perennial. The stem may be branched above, and stems range from 30-120 cm tall. All surfaces of the stem and leaves are persistently white-woolly haired, although the upper leaf surfaces may be less covered, and occasionally may be glabrous. The stems, leaves and flower heads are covered with sharp spines.

The leaves are coarsely toothed to pinnatifid. The teeth or lobes are usually greater than 7 mm wide. The heads are generally several to numerous and found at the ends of the branches. The involucre ranges from 2.4-4 cm high. The outer bracts are spiny tipped as seen in the photos. The flowers are pinkish-purple.

Wavy-leaf thistle is found in dry, open, well-drained habitats, and frequently in sand or gravel in the lowlands and foothills.

Wavy-leaf thistle may be found east of the Cascade Mountains from southern British Columbia south through central Washington to northern Oregon, then east across northern Idaho to the northern Great Plains. It may rarely be found as far south as southeastern Arizona.

Wavy-leaf thistle as seen atop Sourdough Ridge, Asotin Wildlife Area, Asotin County, WA........June 3, 2017.

Two close views of the flower head of wavy-leaf thistle as seen along the Dalles Mt. Road above 2000'.........July 7, 2006. Note the long spines at the tip of each involucral bract as well as the grayish longitudinal markings along the middle of each bract which make the flower heads of this species attractive.

Wavyleaf thistle as observed along the Stubblefield Trail in forest east of South Pine Lakes, Turnbull National Wildlife Refuge........July 4, 2018.

The photo at left shows a cluster of basal leaves of wavy-leaf thistle as seen along Washington Highway 14 at Milepost 91 above Avery, WA.........October 7, 2006. The photo at right shows a basal cluster of leaves of wavy-leaf thistle as seen in a rocky drainage above the east bank of the John Day River about two and one-half miles downstream of Oregon Highway 206 in Cottonwood Canyon State Park and adjacent BLM lands...........April 9, 2016.

The 3 photos seen above show views (from left to right) of the flower head, a stem leaf and a good view of an entire plant of wavy-leaf thistle as seen at the Sheep Mt. Unit Picnic Area, John Day Fossil Beds National Monument in central Oregon.........May 28, 2007.

An example of wavy-leaf thistle seen along Washington Highway 14 west of Roosevelt, WA........June 16, 2009.