Olneya tesota (ironwood) (palo fierro)

It is a moderate-sized, winter deciduous tree that grows 15-30 feet in height with a spreading crown and this scaly gray bark. Ironwood is sensitive to cold temperatures and does not extend into the Mojave Desert or higher elevations of the Sonoran Desert in Arizona. It favors broad washes and middle slopes of large alluvial fans, often occurring with blue palo verde (Parkinsonia florida). The pinate gray-green leaves of ironwood features a pair of sharp, curved spines beneath each leaf along the major branches and trunk of the tree. Although many desert trees serve an important ecological role as nurse plants-aiding in the establishment of seedlings. Ironwood is also a legume with root nodules that fix nitrogen. The name ironwood come from the extremely high density of its wood, which is so dense that it will sink in water. "California Desert Plants, Philip W Rundel, Robert J Gustafson, Michael E Kauffmann."