Saguaro

This article is about the cactus. For the Palm OS software, see Saguaro (Palm OS). For the baseball team, see Surprise Saguaros.

Saguaro Carnegiea gigantea
File:SaguaroCactusAZ.JPG
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Core eudicots
Order:	Caryophyllales
Family:	Cactaceae
Subfamily:	Cactoideae
Tribe:	Pachycereeae
Genus:	Carnegiea Britton & Rose
Species:	C. gigantea
Binomial name
Carnegiea gigantea (Engelm.) Britton & Rose
File:Carnegiea gigantea range map 3.png
Natural range of Carnegiea gigantea
Synonyms
Cereus giganteus Engelm. Pilocereus engelmannii Lem. Pilocereus giganteus Rumpler

The saguaro (/səˈwɑːroʊ/, Spanish pronunciation: [saˈɣwaɾo]) (Carnegiea gigantea) is an arborescent (tree-like) cactus species in the monotypic genus Carnegiea, which can grow to be over 70 feet (21 m) tall. It is native to the Sonoran Desert in Arizona, the Mexican State of Sonora, and the Whipple Mountains and Imperial County areas of California. The saguaro blossom is the state wildflower of Arizona. Its scientific name is given in honor of Andrew Carnegie.

The common name saguaro came into the English language through the Spanish language, originating in the Mayo language.

Growth

Some saguaros are cristate or "crested" due to fasciation.

Saguaros have a relatively long lifespan. They may grow their first side arm any time from 75–100 years of age, but some never grow one at all. A saguaro without arms is called a spear.

The arms are grown to increase the plant's reproductive capacity (more apices lead to more flowers and fruit). The growth rate of saguaros is strongly dependent on precipitation; saguaros in drier western Arizona grow only half as fast as those in and around Tucson, Arizona. Saguaros grow slowly from seed, never from cuttings. Specimens may live for more than 150 years and grow to be over 40 ft tall. The largest known living saguaro is the Champion Saguaro growing in Maricopa County, Arizona, and is 13.8 m (45.3 ft) tall with a girth of 3.1 m (10 ft). The tallest saguaro ever measured was an armless specimen found near Cave Creek, Arizona; it measured 78 feet (24 m) tall before it blew over in a windstorm in 1986.

Saguaros soak up the rainwater and visibly expand. They conserve the water and slowly consume it.

Genome

The saguaro genome is around 1.5 billion base pairs long (about the half of the human genome's length). Sequencing has revealed that the genome of the saguaro's chloroplast is the smallest known among non-parasitic flowering plants.

Spines

The spines on a saguaro that is shorter than 2 m grow rapidly, up to a millimeter per day. When held up to the light or bisected, alternating light and dark bands transverse to the long axis of spines can be seen. These transverse bands have been correlated to daily growth. In columnar cacti, spines almost always grow in areoles which originate at the apex of the plant. A spine stops growing in its first season. Areoles are moved to the side and the apex continues to grow upwards. Thus, older spines are towards the base of a columnar cactus and newer spines are near the apex. Studies are underway to examine the relationship of carbon and oxygen isotope ratios in the tissues of spines of an individual to its climate and photosynthetic history (acanthochronology).

Flowers

File:Saguaro cactus blossoms.jpg

Saguaro flowers

Edible fruit of the saguaro

Flowers appear in April through June. They are white and open well after sunset and close in mid-afternoon. They continue to produce nectar after sunrise. Flowers are self-incompatible, thus require cross-pollination. Large quantities of pollen are required for complete pollination because many ovules are present. A well-pollinated fruit contains several thousand tiny seeds. Saguaros have a redundant pollination system, i.e. full fruit set is possible even if only a fraction of the pollinating species are present.

Main pollinators are honey bees, bats, and white-winged doves. In most years, diurnal visitors are the main contributors for fruit, most of them honey bees. Other diurnal pollinators are birds such as Costa's hummingbird, the black-chinned hummingbird, the broad-billed hummingbird, the hooded oriole, Scott's oriole, the Gila woodpecker, the gilded flicker, the verdin, and the house finch.

The main nocturnal pollinator is the lesser long-nosed bat, feeding on the nectar. A number of floral characteristics are geared toward bat pollination: nocturnal opening of the flowers, nocturnal maturation of pollen, very rich nectar, position high above ground, durable blooms that can withstand a bat's weight, and fragrance emitted at night. Further, the amino acids in the pollen appear to help sustain lactation in bats.

Fruit

Maricopa women gathering saguaro fruits, photo by Edward S. Curtis, 1907

The ruby red fruits are 6–9 cm long and ripen in June. Each fruit contains around 2000 seeds plus sweet fleshy connective tissue. The fruits are edible and prized by local people.

The fruits cannot be picked by hand, but must be harvested using a pole (often a saguaro rib) 2 to 5 m long, to the end of which is attached another pole.

The O'odham tribes have a long history of saguaro fruit use. The Tohono O’odham tribes celebrate the beginning of their summer growing season with a ceremony using a fermented drink made from the bright red fruit to summon rains, vital for the crops.

Nests

File:DBG SaguaroBoot.jpg

Saguaro boot on display at Desert Botanical Garden in Phoenix, AZ

Native birds such as Gila woodpeckers, purple martins, house finches, and gilded flickers live inside holes in saguaros. Flickers excavate larger holes higher on the stem. The nest cavity is deep, and the parents and young are entirely hidden from view. The saguaro creates callus tissue on the wound. When the saguaro dies and its soft flesh rots, the callus remains as a so-called "saguaro boot", which was used by natives for storage.

The Gila woodpeckers (Melanerpes uropygialis) create new nest holes each season rather than reuse the old ones, leaving convenient nest holes for other animals, such as elf owls, flycatchers, and wrens. In recent years, early-breeding, aggressive, non-native birds have taken over the nests to the detriment of elf owls that breed and nest later.

Laws

Harming a saguaro in any manner, including cactus plugging, is illegal by state law in Arizona, and when houses or highways are built, special permits must be obtained to move or destroy any saguaro affected. Exceptions to this general understanding exist; for example, a private landowner whose property is 10 acres or less, where the initial construction has already occurred, may remove a saguaro from the property. This is common when the cactus falls over in a storm, its location interferes with a house addition, or it becomes a potential hazard to humans.

Ethnobotany

• The saguaro is an important source of food and shelter for the Tohono O’odham. Saguaro spines are sometimes used as sewing needles and the ribs are used to make harvesting tools.
• The ribs of the saguaro were used for construction and other purposes by Native Americans. A fine example can be seen in the roofing of the cloisters of the Mission San Xavier del Bac on the Tohono O'odham lands near Tucson.
• The Seri people of northwestern Mexico used the plant, which they call mojépe, for a number of purposes.

Location

The saguaro is often used as an emblem in commercials and logos that attempt to convey a sense of the Southwest, even if the product has no connection to Arizona or the Sonoran Desert. For instance, no naturally occurring saguaros are found within 250 miles (400 km) of El Paso, Texas, but the silhouette is found on the label of Old El Paso brand products. Though the geographic anomaly has lessened in recent years, Western films once enthusiastically placed saguaros in Monument Valley of Arizona, as well as New Mexico, Utah, and Texas. The Dallas, Texas-based band, Reverend Horton Heat, pokes fun at this phenomenon in their song "Ain't no Saguaro in Texas". No wild saguaros are found anywhere in New Mexico, Texas, Colorado, Utah, or Nevada, nor in the high deserts of northern Arizona.

Saguaro gallery

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  Saguaro silhouette at sunset

• Saguaro Cactus AZ.jpg

  Saguaro towering over a 6-ft man

• Saguaro5763.jpg

  Mature five-armed in flower

• Saguaro-3.jpg

  Snow-covered saguaro near Tucson. Saguaros can survive a few hours of below-freezing temperature.

• Saguaro1a.jpg

  Needles of a saguaro, Paradise Valley, Arizona

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  Saguaro flowers, Scottsdale, Arizona

• Dead saguaro1.jpg

  The bare wooden ribs of a dead saguaro

• Saguaro Unusual.JPG

  Unusually-formed crested or cristate saguaro near Kino Bay, Sonora

See also

• Arizona-Sonora Desert Museum
• Desert Botanical Garden
• Saguaro National Park

Bibliography

• Benson, L. (1981). The Cacti of Arizona. University of Arizona Press. ISBN 0-8165-0509-8.
• Drezner TD (2005) Saguaro (Carnegiea gigantea, Cactaceae) growth rate over its American range and the link to summer precipitation. Southwest Nat 50:65–68.

External links

• Flora of North America: Carnegiea gigantea
• Jepson Flora Project: Carnegiea gigantea
• Calphotos: Carnegiea gigantea
• USDA Plants Profile: Carnegiea gigantea
• Saguaro cactus.net