''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, and northwestern Chihuahua (state), Chihuahua.
[Flora of North America]
''Cirsium arizonicum''
/ref>[Jepson Flora]
''Cirsium arizonicum''
/ref>
''Cirsium arizonicum'' is a herbaceous plant that can be either biennial plant, biennial or perennial plant, perennial, reaching 30–150 cm in height. The spiny leaf, leaves 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 floret, 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 Variety (biology), varieties have been identified:][
* ''Cirsium arizonicum'' var. ''arizonicum'' (syn. var. ''nidulum'' (M.E.Jones) S.L.Welsh) – Arizona, New Mexico, California, Nevada, Utah, Sonora, Chihuahua (state), Chihuahua
* ''Cirsium arizonicum'' var. ''bipinnatum'' (Eastwood) D.J.Keil. Four Corners thistle – Arizona, New Mexico, Colorado, Utah, Sonora
* ''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, Sonora; this variety is found on both rims of the Grand Canyon and for a short distance below.]
References
{{Taxonbar, from=Q5122050
Cirsium, arizonicum
Flora of the Southwestern United States
Flora of Mexico
Plants described in 1874
Taxa named by Asa Gray