The Saguaro Cactus is found only in the Sonora Desert, from sea-level to elevations of approximately 4,000 feet, and limited by freezing winter temperatures. Though their habitat is threatened by human encroachment, the Saguaro is a common cactus and is not endangered. They are a protected species in the confines of Arizona’s Saguaro National Park.
Though it may eventually grow as tall as a 2 story house, the Saguaro is a very slow-developing cactus that only grows between 1 and 1 1/2 inches in the 1st 8 years of its life.
Its initial survival strategy involves finding protection under the bows of a “nurse tree”.
Species of trees used by the Saguaro in this manner include the Palo Verde, the Ironwood and the Mesquite. Often, as the Saguaro grows ever-larger, the nurse tree is killed as the cactus monopolizes all the nutrients and water in the soil. The Saguaro cactus is considered and adult at 125 years old. Its life span is normally between 150 and 175 years, though some are thought to be as old as 200. The Saguaro cactus has a number of distinctive physical features. The roots of the Saguaro grow in a radial pattern, the better to absorb moisture. Pleats on the cactus’ surface can expand to store enormous amounts of water, which comprise most of its bulk. Inside the cactus are a number of interconnected woody struts or ribs, numbering the same as the cactus’ pleats, which provide the structural stability needed to support its great weight. When the cactus reaches approximately 35 years of age it begins to produce flowers, normally on the tips of its branches and its trunk, and continues to do so for the rest of its life. The famous arm-like branches of the Saguaro begin to appear when the cactus is between 50 and 100 years old, depending on the amount of precipitation its habitat receives. Damage or mutation sometimes causes the formation of rare fanlike crests on the top of the cactus.
The Saguaro cactus is an important source of food and shelter for a variety of Arizona wildlife. Birds as diverse as the Gila Woodpecker and the Red-tailed Hawk make their nests in these cacti (one on the inside, one on the outside). Birds, coyotes and other animals eat the Saguaro’s fruit when it ripens in the late summer. The cactus’ pulpy flesh is also a food-source for everything form large animals like deer and Bighorn Sheep to rodents like jackrabbits and packrats. Local peoples also use the fruit as a foodstuff.
From April to June the bats, birds and insects that feed on the nectar of the Saguaros’ large, white flowers help to pollinate the cacti. When animals eat the Saguaro’s fruit its roughly 2,000 little black seeds pass harmlessly and unharmed through their digestive systems to be scattered throughout the Sonora Desert in the creatures’ droppings. Though only a tiny number of seeds take root, and few cacti survive to reach their gigantic potential, enough do to ensure the Saguaro’s status of the American King of Cacti.
