Carnegiea gigantea

Carnegiea gigantea, commonly known as the saguaro (pronounced /səˈwɑroʊ/) is a large tree-sized cactus that is the only species in the Carnegiea genus. It is native to the Sonoran Desert in Arizona, a small part of Baja California in the San Felipe Desert, and in a small area of California. The saguaro blossom is the state Wildflower of Arizona.

The common name, saguaro came to the English language through the Spanish language. Its true etymology remains unknown.

Growth
Saguaros have a relatively long lifespan, with some specimens living up to 150 years. They take up to 75 years to develop one side arm, which are grown to increase reproductive capability (more apices equal more flowers and fruits). The growth rate of a saguaro strongly depends upon the amount of precipitation; saguaros in the drier part of Arizona grow only half as fast as those in and around Tucson, Arizona. This species can grow anywhere from 15 to 50 feet tall; the largest recorded saguaro is the Champion Saguaro, standing at 45.3 feet tall, with a girth of 10 feet. It is currently growing in Maricopa County, Arizona. The saguaro will grow slowly by seed, and not at all by cuttings.

Spines
The spines of the saguaro have a height of less than 2 meters, but grow rapidly, up to a millimeter each day. When held up to the light or bisected, alternating light and dark bands transverse to the long axis of the spine can be seen. These bands have been correlated to daily growth. In columnar cacti, spines will almost always grow in aureoles, which originate at the plant's apex. Individual spine growth reaches mature size in the first season and then ceases to continue growing. Areoles are moved to the sides and the apex continues to grow upwards. Thus, the older spines are near the base of the columnar cactus while the newer spines are closer to the apex. Current studies are underway to explain the past climate and photosynthetic history of the plant (acanthochronology).

Flowers
The flowers are colored white and yellow, and bloom during nights between April and June. In late June, these flowers will mature into ruby-colored fruits. Saguaro flowers are self incompatable, and require cross pollination. Large quantities of pollen are needed for complete pollination, because there are numerous ovules. A well-pollinated fruit may contain several thousand seeds.

The major pollinators of the saguaro are bats, primarily the lesser long-nosed bat (Leptonycteris yerbabuenae), which feeds on the nectar from the flowers, which are open at night, and sometimes in the mornings. There are several floral characteristics geared to pollination via bats, such as nocturnal opening of the flowers, nocturnal maturation of pollen, very rich nectar, the position high above th ground, durable blooms that can withstand the weight of the bat, and the fragrance which is emitted at night. One additional evidence is that the amino acids in the pollen seem to help sustain lactation in bats. The flowers remain opening during the day and continue producing nectar after sunrise. Doves and bees appear to be the main daytime pollinators.

Fruit
The ruby red fruit ripen during June. Each fruit contains about 2000 tiny seeds and a fleshy tissue. The fruit are edible and prized by local people, using the fruits sometimes in foods. The O'odham tribes have used the saguaro's fruit for a long time.

Ecological relationships
Several species of bats, doves, and bees pollinate the saguaro, due to its self-incompatibility.

The saguaro provides homes for several native birds, such as Gila woodpeckers, purple martins, house finches, and gilded flickers, which will excavate holes into the cactus. The Gilded Flickers will excavate large holes high on the saguaro's stem. The nest cavity is deep, and the parents and young are completely hidden from view. The saguaro will then create a callus tissue over its wound. When the saguaro dies, its soft flesh rots, but the callus remains behind, a so-called "saguaro boot", which was used by native people for storage.

The Gila woodpeckers will create new nest holes each season rather than reusing old ones, leaving convenient nest holes for other animals, especially elf owls. Recently, early-breeding, aggressive, non-native birds have taken over the nests of the elf owls who breed and nest later.

Laws
Harming a saguaro, including cactus plugging is illegal by state law in Arizona, and when houses or highways are being built, a special permits must be obtained to move or destroy any saguaro in the way.

Location
The saguaro is found commonly in Arizona, but is also found in Baja California and California.

This plant is sometimes used as an emblem in commercials and logos to convey a sense of the southwest, even if the product has no connection to Arizona or the Sonoran Desert. For instance, no saguaros are found within 250 miles of El Paso, Texas, but the silhoutte is found on the label of some Old El Paso products. Though the geographic anomaly has lessened in recent years, Western films once placed saguaros in Monument Valley of Arizona, as well as in New Mexico, Utah, and Texas. There are no wild saguaros anywhere in such western U.S. states as Texas, Colorado, Utah, New Mexico, or Nevada, nor in the high deserts of northern Arizona.

Ethnobotany

 * The ribs of the saguaro were once used for construction and other purposes by Native Americans that inhabited the areas where the saguaro live.
 * The Seri people of Mexico used the plant for numerous reasons.
 * Saguaro boots used for storage, but are now sold as curiosities.
 * The fruit is edible.