Saguaro Cactus – Desert Botanical Garden, Papago Park, Phoenix, Arizona

The saguaro cactus (Carnegiea gigantea) is one of the defining plants of the Sonoran Desert. Indeed, they are found almost exclusively in the Sonoran Desert. The most important factors for their growth are water and temperature. If the elevation is too high, the cold weather and frost can kill the saguaro. Although the the Sonoran Desert experiences both winter and summer rains, it is thought that the Saguaro obtains most of its moisture during the summer rainy season.

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. Saguaros are covered with protective spines, white flowers in the late spring, and red fruit in summer.

Although the saguaro is the largest cactus in the United States, it grows very slowly. A 10 year old plant might only be 1.5 inches tall. Saguaro can grow to be between 40-60 feet tall (12-18m). Most of the saguaros roots are only 4-6 inches deep and radiate out as far from the plant as it is tall. There is one deep root, or tap root that extends down into the ground more than 2 feet. When rain is plentiful and the saguaro is fully hydrated it can weigh between 3200-4800 pounds. With the right growing conditions, it is estimated that saguaros can live to be as much as 150-200 years old. After the saguaro dies its woody ribs can be used to build roofs, fences, and parts of furniture. The holes that birds nested in or "saguaro boots" can be found among the dead saguaros. Native Americans used these as water containers long before the canteen was available.