There are three species, ranging from North America to South America. The species of allenrolfea are subshrubs or shrubs with erect or decumbent growth. The stems are much branched, succulent, glabrous and appear to be articulated. The alternate leaves are sessile and stem-clasping, fleshy, glabrous, their blades reduced to small, broadly triangular scales, with entire margins and acute apex. The inflorescences are terminal spikes with spirally arranged flowers. Cymes of three or five flowers are sitting in the axils of deciduous, peltate, fleshy bracts. The fruit in an ovoid, compressed utricle with membranous pericarp. The erect seed is brown or reddish brown, oblong, with smooth surface.