The saguaro is a large, tree-sized cactus species native to the Sonoran Desert in the U.S. state of Arizona. The saguaro is a large, tree-sized cactus species native to the Sonoran Desert in the U.S. state of Arizona. Some specimens may live for more than 150 years. The largest known saguaro is the Champion Saguaro. It grows in Maricopa County, Arizona, and is 13.8 meters (45.3 ft) tall with a girth of 3.1 meters (10 ft).