''Cirsium arizonicum'', the Arizona thistle, is a

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

n species of thistle in the family Asteraceae, native to the

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

and northwestern Mexico. It has been found in Arizona, southeastern California, New Mexico, Nevada, Colorado, Utah,

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is d ...

, and northwestern

Chihuahua Chihuahua may refer to: Places *Chihuahua (state), a Mexican state **Chihuahua (dog), a breed of dog named after the state **Chihuahua cheese, a type of cheese originating in the state **Chihuahua City, the capital city of the state **Chihuahua Mun ...

.Flora of North America
''Cirsium arizonicum''
/ref>Jepson Flora
''Cirsium arizonicum''
/ref> ''Cirsium arizonicum'' is a

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

plant that can be either biennial or perennial, reaching 30–150 cm in height. The spiny

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are oblong-obovate with pinate lobes; the basal leaves are larger, 10–40 cm long, while leaves on the upper stem can be only 3 cm long. The inflorescence is 3–4 cm in length and 1.5–2 cm diameter, red to pink or purple, with all the florets of similar form (no division into disc and ray florets); individual plants are very variable in the number of heads produced, from one to 100. Flowering is from mid spring to mid fall. The species occurs in mountains, at elevations of 900–3,600 m. Five varieties have been identified: * ''Cirsium arizonicum'' var. ''arizonicum'' (syn. var. ''nidulum'' (M.E.Jones) S.L.Welsh) – Arizona, New Mexico, California, Nevada, Utah,

* ''Cirsium arizonicum'' var. ''bipinnatum'' (Eastwood) D.J.Keil. Four Corners thistle – Arizona, New Mexico, Colorado, Utah,

* ''Cirsium arizonicum'' var. ''chellyense'' (R.J.Moore & Frankton) D.J.Keil (syn. ''C. chellyense'' R.J.Moore & Frankton) Navajo thistle – Arizona, New Mexico * ''Cirsium arizonicum'' var. ''rothrockii'' (A.Gray) D.J.Keil (syn. ''C. rothrockii'' (A.Gray) Petrak). Rothrock's thistle – Arizona, New Mexico,

; this variety is found on both rims of the Grand Canyon and for a short distance below. * ''Cirsium arizonicum'' var. ''tenuisectum'' D.J.Keil. Desert mountains thistle – California, Nevada,

References

{{Taxonbar, from=Q5122050 arizonicum Flora of the Southwestern United States Flora of Mexico Plants described in 1874 Taxa named by Asa Gray