Cirsium ownbeyi is a rare North American species of flowering plant in the aster family known by the common name Ownbey's thistle. It is native to the United States, where it has a narrow distribution in northeast Utah, southwest Wyoming, and northwest Colorado. There are almost 30 known populations, with a total of over 25,000 individuals.
Cirsium ownbeyi is a perennial herb growing 30 to 70 centimeters (12-28 inches) tall from a taproot and branched caudex. There are one or more erect stems. The leaves are up to 30 centimeters (12 inches) long. The flower heads are oval and up to 2.5 centimeters (1 inch) long and wide. They are coated in green phyllaries with spines up to a centimeter long. The head contains white, pink, or purplish flowers up to 2 centimeters long. Blooming occurs in June through August. The fruit may be 2 centimeters long including its long pappus.
This species grows in Dinosaur National Monument, where it is threatened by disturbance caused by park visitors. It is also threatened by the seed-eating weevil Rhinocyllus conicus, which was introduced to the area as an agent of biological pest control against musk thistle.
- Cirsium ownbeyi. The Nature Conservancy.
- Biota of North America Program 2014 county distribution map
- Cirsium ownbeyi. Flora of North America.
- Welsh, Stanley Larson. 1982. Great Basin Naturalist 42(2): 200–201
- Cirsium ownbeyi. Center for Plant Conservation.