''Cirsium ownbeyi'', or Ownbey's thistle, is a rare North American species of flowering plant in the family Asteraceaey. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the United States, where it has a narrow distribution in northeast

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, southwest

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

, and northwest

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

. There are around 30 known populations with a total of approximately 25,000 individuals.''Cirsium ownbeyi''.
The Nature Conservancy.

Description

''Cirsium ownbeyi'' is a

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...

herb growing 30 to 70 centimeters (12-28 inches) tall from a

taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...

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 In botanical terminology, a phyllary, also known an involucral bract or tegule, is a single bract of the involucre of a composite flower. The involucre is the grouping of bracts together. Phyllaries are reduced leaf-like structures that form one o ...

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.''Cirsium ownbeyi''.
Flora of North America.Welsh, Stanley Larson. 1982. Great Basin Naturalist 42(2): 200–201

Habitat

This plant grows in

sagebrush Sagebrush is the common name of several woody and herbaceous species of plants in the genus '' Artemisia''. The best known sagebrush is the shrub '' Artemisia tridentata''. Sagebrushes are native to the North American west. Following is an al ...

, juniper-dominated habitat, and

riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks a ...

zones. The substrate is usually

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

, but sometimes

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

.''Cirsium ownbeyi''.
Center for Plant Conservation.

Conservation

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 Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and herbivorous. Approximately 97,000 species of weevils are known. They belong to several families, ...

Rhinocyllus conicus ''Rhinocyllus conicus'' is a species of true weevil. It is best known as a controversial agent of biological pest control which has been used against noxious thistles in the genera ''Carduus'', ''Cirsium'', ''Onopordum'', and ''Silybum''. The a ...

'', which was introduced to the area as an agent of biological pest control against musk thistle {''Carduus nutans'').

References

{{Taxonbar, from=Q5122066 ownbeyi Plants described in 1982 Flora of the Western United States Endemic flora of the United States