Carnegiea gigantea, Giant Saguaro

Southwest Desert Flora

Home to the plants of the Sonoran, Chihuahuan and Mojave Deserts

Cirsium ochrocentrum, Yellowspine Thistle

Centaurea melitensis, Maltese Star-thistle

Centaurea melitensis, Maltese Star-thistle, Southwest Desert Flora Centaurea melitensis, Maltese Star-thistle, Southwest Desert Flora    Centaurea melitensis, Maltese Star-thistle, Southwest Desert Flora

Centaurea melitensis, Maltese Star-thistle, Southwest Desert Flora    Centaurea melitensis, Maltese Star-thistle, Southwest Desert Flora

Scientific Name: Centaurea melitensis
Common Name: Maltese Star-thistle
Also called: Maltese Star-thistle, Maltese Star Thistle, Malta Starthistle, Napa Thistle, Spotted Knapweed, and Tocalote, (Spanish: Cardo)
Family: Asteraceae, Sunflower Family
Synonyms: ( )
Status: Introduced, European.
Duration: Annual or biennial.
Size: To 3 feet.
Growth Form: Forb/herb; stems erect, stiff, mostly 1 stem, large plants openly branched.
Leaves: Green, grayish green; alternate; fine hairs, basal rosette pinnately divided, oblong or oblanceolate, lower leaves usually dried by bloom period; upper leaves variable, linear or elliptical, margins smooth, toothed or wavy.
Flower Color: Yellow; discoid flowers only, numerous, corollas yellow, 1 or more spiny flowering heads; spine tipped bracts or phyllaries subtending flower heads, cobwebby, straw colored, central spin longest, slender and recurved; fruit is an achene, fine tan or white pappus bristles.
Flowering Season: May to July.
Elevation: To 4,500 feet.
Habitat Preferences: Various habitats, lower and upper deserts, pinyon-juniper communities, chaparral and grasslands, disturbed areas, roadsides and agriculture areas.
Recorded Range: Primarily a western invasive species in North America quickly spreading east of the Mississippi River extending currently to Massachusetts. Invasive also in Hawaii. In central, south northwest and northeast Arizona.

U.S. Weed Information: Centaurea melitensis can be weedy or invasive as noted by the USDA, Natural Resources Conservation Service. It is considered a noxious weed in 46 states. Plants included here may become weedy or invasive.
Invasive/Noxious Weed Information: Centaurea melitensis is listed by the USDA, Natural Resources Conservation Service as a Federal and State Noxious Weed.
Wetland Indicator: No data available.
Threatened/Endangered Information: No data available.

Genus Information: 37 species in Centaurea across the North America, Newfoundland and Greenland. Only 2 native species in North America, 8 species in Arizona, 2 native species native in Arizona:
Centaurea Americana, American Star-thistle and
Centaurea rothrockii, Rothrock's Knapweed (AZ, NM).

Comments: Maltese Thistle is an aggressive weed introduced from Europe and Africa and it continues to spread across North America where it is already listed as a noxious weed in most states. The numerous common names of a plant is often a clue as to its economic significant or importance across its range, either positive or notoriously, such as the case for Maltese Thistle.

Ethno botanical uses have been described for California Brickellbush; view the complete species account from Native American Ethnobotany, University of Michigan, Dearborn.

Date Profile Completed: 8/13/2012; Updated, 07/25/2015
References:
U.S. Dept. of Agriculture, Natural Resources Conservation Service on-line database
Arizona Flora, Kearney, Thomas H., Peebles, Robert H., 1960, University of California Press, Berkley and Los Angeles
The Jepson Manual, Citation: http://ucjeps.berkeley.edu/interchange/I_treat_indexes.html Mon Aug 13 10:30:39 2012
David J. Keil, Jörg Ochsmann, FNA | Family List | FNA Vol. 19, 20 and 21 | Asteraceae | Centaurea, Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 16+ vols. New York and Oxford. (accessed 08/013/2012).
SEINet for synonyms, scientific names and recorded geographic locations, http://swbiodiversity.org/seinet/
USDA - http://plants.usda.gov/core/profile?symbol=ceme2 accessed 08/01/2014 Assorted authors. State noxious weed lists for 46 states. State agriculture or natural resource departments. Nevada: Malta thistle Noxious weed - New Mexico: Maltastarthistle - Class B noxious weed