1. Description
    Spines  Flowers  Fruit  Genome 

2. Distribution and habitat

3. Nests

4. Conservation

5. Ethnobotany

6. Gallery

7. References

8. External links

The saguaro ({{IPAc-en|s|ə|ˈ|w|ɑː|r|oʊ}}, {{IPA-es|saˈɣwaɾo}}) (Carnegiea gigantea) is an arborescent (tree-like) cactus species in the monotypic genus Carnegiea, which can grow to be over {{convert|40|ft|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. In 1994, Saguaro National Park, near Tucson, Arizona, was designated to help protect this species and its habitat.

The image of the saguaro is indelibly linked with that of the American Southwest, especially in western films. The common name saguaro came into the English language through the Spanish language, originating in the Mayo language.

Saguaros have a relatively long lifespan, often exceeding 150 years. They may grow their first side arm any time from 75–100 years of age, but some never grow any arms. A saguaro without arms is called a spear. Arms are developed to increase the plant's reproductive capacity, as more apices lead to more flowers and fruit.

A saguaro is able to absorb and store considerable amounts of rainwater, visibly expanding in the process, while slowly using the stored water as needed. This characteristic enables the saguaro to survive during periods of drought.

Description

The saguaro is a columnar cactus that grow notable branches, usually referred to as arms. As many as 25 arms may grow on one plant. They are slow growing but routinely live to 150 or 200 years old. They are the largest cactus in the United States. Their roots are shallow yet wide, growing only to {{Convert|6|in|mm|abbr=}} deep, but extend as wide as the plant is tall.^[3]

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. Saguaros grow slowly from seed, never from cuttings, and grow to be over {{convert|40|ft|m|1|abbr=off}} in height.^[4] The largest known living saguaro is the Champion Saguaro growing in Maricopa County, Arizona, measuring {{convert|13.8|m|ft|1|abbr=off|order=flip}} high with a girth of {{convert|3.1|m|ft|abbr=off|order=flip}}. The tallest saguaro ever measured was an armless specimen found near Cave Creek, Arizona. It was {{convert|78|ft|m|1|abbr=off}} in height before it was toppled in 1986 by a windstorm.^[5] When rain is plentiful and the saguaro is fully hydrated it can weigh between {{convert|3200|-|4800|lb}}.{{Citation needed|date=March 2019}}

Spines

The spines on a saguaro can grow up to {{convert|1|mm}} 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).^[6]

Flowers

The white, waxy flowers appear in April through June, opening well after sunset and closing in mid-afternoon. They continue to produce nectar after sunrise.^[7]

Flowers are self-incompatible, thus requiring cross-pollination. Large quantities of pollen are required for complete pollination because many ovules are present. This pollen is produced by the extremely numerous stamens, which in one notable case totaled 3,482 in a single flower.^[8] 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, mostly honey bees, are the main contributors for fruit. 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.^[9]

The primary 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

The ruby red fruits are {{convert|6|to|9|cm|in|order=flip}} long and ripen in June, each containing around 2,000 seeds, plus sweet, fleshy connective tissue. The fruits are edible and prized by local people.

The fruits are often out of reach and are harvested using a pole (often a saguaro rib) {{convert|2|to|5|m|ft|0|order=flip}} long, to the end of which is attached a smaller pole, crosswise. This pole is used to knock the fruits free.

The O'odham tribes have a long history of saguaro fruit use.^[10] 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 their crops.

Genome

The saguaro genome is around 1 billion base pairs long.^[11] Sequencing has revealed that the genome of the saguaro's chloroplast is the smallest known among non-parasitic flowering plants.^[12]

Distribution and habitat

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.^[13][14] Though the geographic anomaly has lessened in recent years, Western films once enthusiastically placed saguaros in the 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".^[15] No wild saguaros are found anywhere in New Mexico, Texas, Colorado, Utah, or Nevada, nor in the high deserts of northern Arizona.^[14]

Saguaros are endemic to the Sonoran Desert and are found only in western Sonora in Mexico and in southern Arizona in the US {{En dash}} although plants are occasionally found in southeastern California. Elevation is a limiting factor to its environment, as the Saguaro is sensitive to extended frost or cold temperatures. Within their range, they are more ^[3]

Nests

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.^[16] 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 birds, such as elf owls, flycatchers, and wrens.^[17] 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.

Conservation

Harming or vandalizing a saguaro in any manner, such as shooting them (sometimes known as 'cactus plugging')^[18] is illegal by state law in Arizona. When houses or highways are built, special permits must be obtained to move or destroy any saguaro affected.^[19] Exceptions to this general understanding exist; for example, a private landowner whose property is {{convert|10|acre|ha}} or less, where the initial construction has already occurred, may remove a saguaro from the property.^[20] 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.^[21]

In 1982, a man was killed after damaging a saquaro. David Grundman was shooting and poking at a saguaro cactus in an effort to make it fall. An arm of the cactus, weighing {{convert|500|lb|kg}} fell onto him, crushing him and his car. The trunk of the cactus then also fell on him.^[18][22] The Austin Lounge Lizards wrote the song "Saguaro" about this death.^[22]

Contrary to published statements,^[23] there is no law mandating prison sentences of 25 years for cutting a cactus down; however it is considered a class four felony with a possible 3 year, 9 month maximum sentence.^[24]

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.
• The ribs of dead saguaros are used as building material.^[3]
• Cactus boots, excavated by birds{{Which|date=March 2019}} and taken from dead saguaros, have been used by native peoples as water containers.^[3]

Gallery

References

• 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.
• {{cite book |last=Felger |first=Richard |author2=Mary B. Moser. |title=People of the desert and sea: ethnobotany of the Seri Indians |location=Tucson |year=1985 |publisher=University of Arizona Press}}

External links

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

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