The Barrel Cactus (Ferocactus wislizeni) and the Saguaro Cactus (Carnegiea gigantea) both grow in the desert of the American Southwest. These spiny plants are very diverse in their growth habit. The Saguaro Cactus is native to the Sonoran desert, which covers the southwestern third of Arizona, the southeastern tip of California, and northwestern Mexico. The Barrel Cactus also grows across the Sonoran desert, but its range extends eastward across southern New Mexico to western Texas.
Short and Round
Mature Barrel Cactus and Saguaro Cactus are very different in shape and size. A mature Barrel Cactus typically reaches about 5 feet (1.5 m) in height, but under ideal conditions, it can reach as much as 10 feet (3 m) high. A Barrel Cactus grows round and wide, with a diameter of more than 30 inches (75 cm), giving this plant its characteristic resemblance to a barrel. The Barrel Cactus thrives in U.S. Department of Agriculture hardiness zones 8 to 11.
Tall With Branches
The Saguaro is an icon of the American Southwest. It grows in USDA hardiness zones 9 and 10. It grows much taller than the Barrel Cactus, reaching heights of more than 50 feet (50 m). It is narrower in proportion to its height than a Barrel Cactus. Another major difference is that the Saguaro grows several erect lateral branches that parallel the main trunk, giving this plant its characteristic resemblance to a human hand. A Barrel Cactus doesn't grow branches.
The Barrel Cactus and Saguaro Cactus both produce edible fruit relished by desert wildlife. Barrel Cactus fruits are yellow, oval, and about 2 inches (5 cm) in diameter. They come from orange flowers that grow in a circle at the top of the plant. The Saguaro Cactus' fruits are oval, spiny, red, and 4 inches (10 cm) long, produced from white flowers that grow on the ends of the main trunk and branches.
Roots and Spines
A Barrel Cactus' root system is shallow, typically only about 2 inches (5 cm) below the soil surface, and spreads out laterally from the bottom of the barrel. A Saguaro Cactus has a more extensive and deep root system with lateral branches spreading out from a central taproot to a distance roughly twice the plant's height. The spines of a Barrel Cactus are very dense and curve inward in a hook shape, while the spines of the Saguaro are less dense and are straight.