Koeberlinia spinosa is a species of flowering plant native to the southwestern United States and northern Mexico known by several common names, including crown of thorns, allthorn, and crucifixion thorn. It is the sole species of the monotypic genus Koeberlinia, which is sometimes considered to be the only genus in the plant family Koeberliniaceae. Alternately it is treated as a member of the caper family. This is a shrub of moderate to large size, sprawling to maximum heights over 4 m (13 ft). It is entirely green while growing and is made up of tangling straight stems which branch many times. The tip of each rigid stem branch tapers into a long, sharp spine. Leaves are mainly rudimentary, taking the form of tiny deciduous scales. Most of the photosynthesis occurs in the green stem branches. The shrub blooms abundantly in white to greenish-white flowers. The fruits are shiny black berries each a few millimeters long; they are attractive to birds.