The Saguaro Cactus

The hot cruel sun of the desert beats down on long prickly arms that extend skyward from tall green trunks. Here in the Sonoran Desert, located on the border of the United States and Mexico, the air is dry and every drop of water is fought for viciously. In this arid climate, saguaro cacti battle for survival.

Every part of the cactus helps the plant gather and keep what little water is available. Unlike trees, which often have roots extending dozens of feet underground to reach deep reserves of water, saguaro cacti have very short roots that spread out wide to better capture rainwater. The trunk of the cactus is corrugated, or folded, almost like an accordion. When the cactus is full of water, the trunk can expand to store water for use in drier times. The waxy green surface of the cactus' trunk prevents the cactus from drying out and losing the water stored within.

Many species of cacti have similar methods of storing water in dry climates. The saguaro cactus is unique, however, in its incredible size and growth. Scientists think that saguaro cacti can live to be up to 200 years old. Cacti this old can be more than 40 feet tall and weigh more than a car. Despite this impressive size, saguaro cacti start from humble beginnings. The cactus begins life under the shade of a desert tree, called a nurse tree, that will shield it from the hot sun and from the hungry glances of animals. At ten years old, the saguaro is only about the size of a thumb. As the little cactus grows larger and larger, it begins to demand more water from the soil. Soon, the nurse tree that sheltered the young plant is deprived of water and dies.

As the saguaro grows, it becomes a source of food and shelter for a multitude of desert creatures. Although the prickly spines of the cactus deter animals while the cactus is young, as the saguaro ages, the spines spread out. This allows the first brave explorer, the Gila woodpecker, to approach the trunk. The woodpecker bores a hole in the trunk to make its home. In following years, owls, finches, and sparrows will use the hole to raise their young. When the saguaro matures and begins to produce flowers, bats will visit by night to eat the sweet nectar. In the summertime, the saguaro fruit becomes a tasty snack for many reptiles, insects, and mammals. In times of drought, rodents, deer and sheep will eat chunks of the cactus’ water-filled trunk to quench their thirst. Young cacti can even be found sprouting within the sheltered cavities, or holes, in the trunks of older saguaro. In the harsh environment of the Sonoran Desert, the strong saguaro is an oasis of life.