New Mexican locust, sometimes (though erroneously) called al- 

 garoba or, colloquially, agarroba, is a large, thorny shrub or small 

 tree, varying from several feet up to 20 or 25 feet in height. With 

 the exception of the little known southern New Mexican species 

 R. rusbyi, it is the only species of the genus occurring naturally in 

 the Western States. It ranges from western Texas to southern Colo- 

 rado, southern Nevada, and south into the mountains of northern 

 Sonora. The altitudinal distribution of this species varies from about 

 4,000 to 9,000 feet. At the lower altitudes it grows chiefly in canyon 

 bottoms and on north slopes, but at the higher elevations the species 

 occurs also on dry ridge tops and rocky slopes. Scattered patches 

 of this shrub are common in open ponderosa pine stands, and also 

 occur, on some small scale, in openings in aspen and spruce-fir types. 



This shrub is usually considered as poor to fair forage for cattle 

 and horses. Cattle seem to relish the flowers ; both cattle and horses 

 crop the leaves to some extent. The new growth is most palatable 

 and is grazed in early summer before the thorns develop. Chapline 1 

 designates New Mexican locust as an important browse species of 

 high palatability for goats in the Southwest. Sheep graze it mod- 

 erately on some ranges, particularly when there is a scarcity of 

 other browse forage. This plant has been heavily grazed and seri- 

 ously damaged by deer on the Kaibab National Forest. However, 

 such severe use indicates extreme overstocking; under conservative 

 use by deer the species is utilized rather lightly. Black locust 

 (Rabvnw pseudoacacia) of the Eastern States, often cultivated in the 

 West as a common shade tree, is a closely related species and is 

 recognized as poisonous; there are no indications, however, that 

 New Mexican locust produces undesirable effects upon livestock. 2 



New Mexican locust reproduces by both suckers and seed, and re- 

 covers rapidly from overgrazing, when given opportunity. It is 

 important in erosion control, as it establishes itself readily on rel- 

 atively poor sites, and thrives on steep slopes and gully banks. An 

 attractive shrub, easily transplanted, New Mexican locust is some- 

 times used for ornamental purposes and grows well under cultivation. 



This locust, which usually attains a height of from 10 to 15 feet, 

 grows in clumps, frequently f orming dense thickets that afford good 

 cover for game birds. The trunk is seldom over 4 inches in diameter, 

 and the top is open and spreading. The leaves resemble those of 

 the common black locust very closely; the large and showy flowers 

 varying from a bright to dark rose-pink, or occasionally nearly 

 white, lack the sweet fragrance of the white flowers of black locust. 

 New Mexican locust is easily distinguished from R. rusbyi by the 

 sticky hairs which beset the flowers, seedpods, and flower and fruit 

 stalks. The flowers appear from April to August ; the pods are usu- 

 ally fully formed by the middle of September. 



1 Chapline, W. R. PRODUCTION OF GOATS ON FAR WESTERN RANGES. U. S. Dept. Agr. 

 Bull. 749, 35 pp., illus. 1919. 



2 Dayton, W. A. IMPORTANT WESTERN BROWSE PLANTS. U. S. Dept. Agr. Misc. Pub. 

 101, 214 pp., illus. 1931. 



