Prosopis pubescens, commonly known as screwbean mesquite, is a species of flowering shrub or small tree in the pea family, Fabaceae, that is native to the southwestern United States (Texas, Arizona, New Mexico, California, southern Nevada and Utah) and northern Mexico (Baja California, Chihuahua, Coahuila, Sonora).
This plant grows to about 7 m (23 ft). It has light brown bark, usually short, straight spines 1 to 3 centimeters long, twice-compound leaves, and numerous small yellowish flowers appearing in elongate spikes. The tightly twisted seedpods (legumes) are up to 5 centimeters long and very much resemble turned screws.
This morphology may have been an evolutionary defense against seed predators such as bean weevils (Bruchinae). The seeds germinate after being scarified in the digestive tracts of animals that eat them. The plant also grows in a clockwise spiral.
