Structurally, the giant cactus is well adapted to meet the stern requirements of its habitat. Its widespread root system, as much as 70 feet in diameter, lying close to the surface of the ground, anchors and holds the heavy plant erect. The shallow root system quickly and efficiently collects and channels to the main stem any moisture that may penetrate the topsoil. The trunk and branches have a cylindrical framework of long slender poles or ribs fused at the constricted base. This woody skeleton supports the mass of pulpy tissue, the whole being covered with tough, waxy, spine-bearing “skin.” Numerous vertical ridges, like the pleats of a huge accordion, permit the stems and branches to expand in girth as the tissues swell with water during wet weather and to shrink during times of drought. So efficient is the saguaro’s water-storage system that, even after years of extreme drought, the plant retains enough moisture in reserve to enable it to produce flower buds. The buds appear in vertical rows at the tips of the main stem and branches, a few opening each evening over a period of several weeks in May and June. The flowers, up to 4 inches in diameter, have waxy white petals. This beautiful blossom is the State flower of Arizona. The egg-shaped fruits mature in late June and July, splitting open when ripe to reveal masses of juicy, deep-red pulp filled with tiny black seeds. Pulp and seeds are consumed by several kinds of birds, especially white-winged doves. Many fruits that fall to the ground are promptly eaten by rodents and other animals. Indians, too, eat the fruits. European explorers who followed Coronado’s expedition into this region found peaceful Papagos and Opatas living here, hunting animals and utilizing many native plants. Among the most dependable of Papago food sources was the fruit of the giant cactus. So important was this fruit harvest in their economy that they designated this season as the start of the new year. Today, in some parts of the desert, Pima and Papago Indians still harvest the fruits. The word “saguaro” is believed to derive from a Spanish corruption of a Papago word for the big cactus. [Illustration: Spiny armor of the saguaro.] [Illustration: Saguaro in full bloom.] Saguaros provide not only food for man and beast, but homes for animals. Walk through a giant cactus forest and you will be amazed at the number of holes drilled in these plants. The holes are made by Gila woodpeckers and related gilded flickers, which often relinquish them after one nesting season. The next occupant may be any of a host of desert dwellers, including screech and elf owls, purple martins, and invertebrates. Some birds use the plant as a foundation for their homes. White-winged doves, for instance, often build flimsy stick platforms on the tips of saguaro arms; red-tailed hawks and horned owls construct more substantial nests in the forks.