Flowering cactus (Cleistocactus sepium var.. veintimigliae). The Cleistocactus cacti often form long spiny columns, as seen here. Cacti are found in arid environments, and have tissues adapted to minimise water loss. Cactus leaves are reduced to narrow spines, and the plant surface is covered in a thick, waxy outer layer. Many cacti also have a means of storing water. This variety of Cleistocactus sepium is found only in the Guayllabamba valley in Pichincha, Ecuador.