Cirsium arizonicum, Arizona Thistle
Scientific Name: Cirsium arizonicum
Common Name: Arizona Thistle
Also called: Spanish: Cardo Santo
Family: Asteraceae, Sunflower Family
Synonyms: (Cirsium arizonicum var. arizonicum, C. arizonicum var. nidulum, C. nidulum, Cnicus arizonicus)
Duration: Biennial or perennial.
Size: Up to 4 feet or more.
Growth Form: Subshrub from a tap-rooted caudex or runner roots; spiny all over, basal rosette with 1 or more stems, erect or ascending, tomentose or glabrous; stems wooly to cobwebby.
Leaves: Green; basal leaves sessile, 4 to 8 inches, some lobed, tomentose, spiny throughout; cauline leaves alternate; leaves variable, linear, elliptic or oblong, sharply toothed, upper leaves more glabrous, clasping, spines along margins.
Flower Color: Red, pink, purple or lavender (rarely white); 1 to 100 erect heads; disk flowers only; corolla tube shaped, 1 or several heads on short peduncles; phyllaries green, ovate or lanceolate; fruit is an achene.
Flowering Season: May to October or November.
Elevation: 3,000 to 7,000 feet.
Habitat Preferences: Upper deserts, pine, pinyon-juniper and chaparral communities, sunny open areas, woodland openings and rocky slopes.
Recorded Range: Arizona Thistle is found in the southwestern United States in AZ, CA, NM, NV and UT. In Arizona, it is found in higher elevations in the northern and southern parts of the state. It is also native to northwest Mexico.
North America & US County Distribution Map for Cirsium arizonicum.
U.S. Weed Information: No data available.
Invasive/Noxious Weed Information: In North America the genus Cirsium is listed as a Noxious Weed by the States of Arkansas and Iowa. Plants included here are invasive or noxious.
Wetland Indicator: is on the USDA 2012 National Wetland Plant List. In North America Cirsium arizonicum has the following wetland designations: Arid West, FACU; Great Plains, FAC; Western Mountains, Valleys, and Coast FAC.
Threatened/Endangered Information: No data available.
Genus Information: In North America there are more than 90 species and 113 recorded taxa overall for Cirsium. World wide, The Plant List includes 481 accepted species names and includes a further 812 of infraspecific rank for the genus.
In the Southwestern United States: Arizona has 19 species of Cirsium, California has 26 species, Nevada has 16 species, New Mexico has 19 species, Texas has 12 species, Utah has 23 species. All data is approximate and subject to taxonomic changes.
There are 5 varieties of Cirsium arizonicum in Flora of North America;
Cirsium arizonicum var. rothrockii, (AZ, NM);
Cirsium arizonicum var. arizonicum, (AZ, CA, NM, NV, UT);
Cirsium arizonicum var. chellyense, (AZ, NM)
Cirsium arizonicum var. bipinnatum, (AZ, NM, NV, UT);
Cirsium arizonicum var. tenuisectum, (CA, NV).
Comments: Arizona Thistle characteristics are variable across their relatively wide geographic range with five varieties having been described. The type species is from the Babocomari, Arizona, and Santa Cruz, Sonora (Wright).
The genus Cirsium has achieved adverse notoriety from two introduced European thistles now wide-spread throughout North America; Canadian thistle, Cirsium arvense is listed as noxious in 33 states and Bull Thistle, Cirsium vulgare, is also a noxious weed. However most southwestern native thistles, including Arizona Thistle, are non-aggressive; non-invasive species that have evolved to thrive without becoming weedy in their respective select geographic southwestern ecosystems. Many native thistles are now threatened with some species at risk of extinction.
Cirsium arizonicum has bright red flowers and a long tube making it attractive to hummingbirds and, as with most thistles it is also attractive to many native bees and insects. The Xerces Society for Invertebrate Conservation acknowledges in their 2017 publication "Native Thistles: A Conservation Practitioner's Guide" that "native thistles are misunderstood and wrongly maligned group of wildflowers..." when in fact native thistles provide resources for many species of bees, butterflies and other wildlife which rely heavily on these species plants. "Monarch butterflies visit native thistle flowers more than any other wildflowers in some regions during their migration back to Mexico".
The genus Cirsium is from the Greek word "kirsion" "a kind of a thistle" which is translated from the Greek word "kirsos" meaning "swollen vein or welt"; a reference to their remedy against swollen veins and welts as thistles were quite often used as a remedy for these types of ailments.
The species epithet arizonicum is a direct reference meaning of or from or otherwise honoring Arizona.