''Ambrosia cordifolia'', called the Tucson bur ragweed, is a North American species of plant in the family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

. It is native to northern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

( Sonora, Sinaloa, San Luis Potosí, Guanajuato, Baja California Sur) and the State of

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. ''Ambrosia cordifolia'' is a shrub up to 50 cm (20 inches) tall. Leaves are triangular or heart-shaped.

Flower head A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...

s are small and inconspicuous, as the plant is

wind-pollinated Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including grasses, sedges, and rushes. Other common anemophilous pla ...

. The heads develop into spiny

bur A bur (also spelled burr) is a seed or dry fruit or infructescence that has hooks or teeth. The main function of the bur is to spread the seeds of the bur plant, often through epizoochory. The hooks of the bur are used to catch on to for exam ...

s as the seeds ripen. The reference to the

city of

Tucson , "(at the) base of the black ill , nicknames = "The Old Pueblo", "Optics Valley", "America's biggest small town" , image_map = , mapsize = 260px , map_caption = Interactive map ...

in the common name refers to the species' first discovery by Cyrus G. Pringle in the mountains near Tucson in 1884.Gray, Asa 1884. Synoptical Flora of North America 1(2): 445
as ''Franseria cordifolia''

References

External links

Pollen Library, Tucson Burr-Ragweed (Ambrosia cordifolia)Cabeza Prieta Natural History Association, Sonoran Desert Plants, ''Ambrosia cordifolia'' (Heart-leaf Bur-sage)
cordifolia Flora of Arizona Flora of Baja California Sur Flora of Guanajuato Flora of San Luis Potosí Flora of Sinaloa Flora of Sonora Plants described in 1884 Taxa named by Asa Gray {{Heliantheae-stub