An Illustrated Guide to ARIZONA WEEDS
The University of Arizona Press
COMMON COCKLEBUR-Xanthium strumarium L. (X. saccharatum Wallr.)
DESCRIPTION-Common cocklebur is a coarse bushy annual with stout, usually red-spotted stems, 2 to 3 feet high; reproducing by seed. The large rough glandular green leaves are longstalked. triangular, somewhat lobed, about 2 to 14 inches long, and 1 to 8 inches broad. The short flowering branches arise from the leaf axils along the main stems. The inconspicuous male flowers are grouped into several to many round clusters at the top, with the conspicuous brown female burs at the base. The footballshaped burs, 1/2 to 1 inch or more long, enclose 2 female flowers, and are covered by about 400 stiff, glandular-hairy spines, 1/8 to 1/4 inch long, ending in a hook. The male flowers drop off quickly, but the burs persist, with the 2 blackish achenes. The 2 seeds inside, about 1/2 inch long, remain fertile for many years.
DISTRIBUTION-Common cocklebur grows in moist flooded soil of roadsides, cultivated fields, pastures, and flats throughout the state, particularly troublesome in wet years around water holes on the sheep ranges of northern Arizona; 100 to 6,000 feet elevation; flowering June to October. The vicious burs form tangled clots in the manes, tails, or wool of animals, often resulting in a lower value of the wool.
POISONOUS PROPERTIES-The seeds and the seedling plants of cockleburs are particularly poisonous to hogs; however, sheep, cattle, horses, and chickens have also been poisoned by eating the seedlings. The seeds are rarely eaten; the seedlings contain the poisonous principle which decreases rapidly as the seedling plant grows.
SPINY COCKLEBUR-Xanthium spinosum L.
DESCRIPTION-Only 2 species of cocklebur occur in Arizona, but they do not resemble one another. Spiny cocklebur has I or more stout yellow 3-forked spines, 1/2 to 1 inch or more long, at the base of each leaf. The long narrow pointed leaves, 1 to 5 inches long, mostly 2- to 5-lobed, are silvery white beneath and dark green above, with the midvein white. The short-spired burs are only 1/3 to 1/2 inch long. Spiny cocklebur grows in similar situations as common cocklebur, but is not common. Areas where it is troublesome are the Chino, Skull, and Peeples valleys in Yavapai County; also in Santa Cruz and Pima counties.
Copyright (c) 1972 The Arizona Board of Regents