UNIQUE PLANT OF THE DAY ... The Saguaro Cactus (Carnegiea gigantea) is one of the defining plants of the Sonoran Desert. These plants are large, tree-like columnar cacti that develop branches (or arms) as they age, although some never grow arms. These arms generally bend upward and can number over 25. The roots of saguaro cactus can store up to 8 tons of water, collected during the brief periods of rain. You find this cactus in southern Arizona and western Sonora, Mexico.