An Illustrated Guide to ARIZONA WEEDS

The University of Arizona Press



PEA FAMILY-Leguminosae

CAMELTHORN-Alhagi camelorum Fisch.

DESCRIPTION-A spiny, intricately branched, completely hairless shrub 1 1/2 to 4 feet high, reproducing by seeds, but principally from deep vertical roots and extensive rhizomes. The greenish stems bear slender vicious spines, green with yellow tips, 1/4 to 1 3/4 inches long. The alternate wedgeshaped leaves, yellowish above, bluish green beneath, are 1/4 to 1 1/4 inches long, 1/8 to l/2 inch broad, and have very short stalks.

The small pealike flowers, about 3/8 inch long, are pinkish purple to maroon. These occur on short slender spinetipped branches which arise uniformly and in large numbers along the upper part of the stems. When the pods mature and fall off, these branches become persistent spines.

The reddish brown jointed seedpods are curved upward, and commonly have 1 to 4 seeds, or up to 9. The pod is deeply indented, and each seed is clearly outlined like a bead on a string. The kidneyshaped seed is grayish brown, about l/8 inch long, and 1/12 inch broad.

DISTRIBUTION-Camelthorn, introduced from Asia, grows principally in deep moist soil, but also in dry rocky soil. Abundant in colonies along the banks, bottomlands, and drainage of the Little Colorado and Salt rivers, along canals, irrigation ditches, and sometimes spreading to adjacent cultivated fields; in Navajo, Coconino, Gila, Maricopa, and Yuma counties; 100 to 5,000 feet elevation; flowering May to July, the seedpods persisting until October or November.

The underground roots and rhizomes branch greatly, but usually after they are 2 to 4 feet deep. Once established, a colony increases in size each year. In less than 20 years, the infestation along the canals near Gillespie Dam (Maricopa County) has become continuous for more than l5 miles.

Copyright (c) 1972 The Arizona Board of Regents

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