Saguaro
Saguaro | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Order: | Caryophyllales |
Family: | Cactaceae |
Subfamily: | Cactoideae |
Tribe: | Echinocereeae |
Genus: | Carnegiea Britton & Rose[3] |
Species: | C. gigantea
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Binomial name | |
Carnegiea gigantea | |
Natural range of Carnegiea gigantea | |
Synonyms[4] | |
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The saguaro (
Saguaros have a relatively long lifespan, often exceeding 150 years. They may grow their first side arm around 75–100 years of age, but some never grow any arms. Arms are developed to increase the plant's reproductive capacity, as more
Saguaros have been a source of food and shelter for humans for thousands of years. Their sweet red fleshed fruits are turned into syrup by native peoples, such as the
Description
The saguaro is a columnar cactus that grows notable branches, usually referred to as arms. Over 50 arms may grow on one plant, with one specimen having 78 arms.[6] Saguaros grow from 3–16 m (10–52 ft) tall, and up to 75 cm (30 in) in diameter. They are slow growing, but routinely live 150 to 200 years. They are the largest cactus in the United States.[7][8]
The growth rate of this cactus is strongly dependent on
Height | Age (Years) |
---|---|
0.5 feet (0.15 m) | 9 |
1.0 foot (0.30 m) | 13 |
5.0 feet (1.5 m) | 27 |
10.0 feet (3.0 m) | 41 |
20.0 feet (6.1 m) | 83 |
25.0 feet (7.6 m) | 107 |
30.0 feet (9.1 m) | 131 |
35.0 feet (10.7 m) | 157 |
Saguaros have a very large root network that can extend up to 30 m (100 ft), and long taproots of up to 1 m (3 ft 3 in) deep.[7]
Saguaros may take between 20 and 50 years to reach a height of 1 m (3 ft 3 in).[7] Individual stomatal guard cells and medulla cells can live and function for as long as 150 years,[14] possibly the longest living of all cells, except possibly nerve cells in some tortoises.[citation needed]
As a cactus, it uses crassulacean acid metabolism photosynthesis, which confers high levels of water-use efficiency. This allows the saguaro to only transpire at night, minimizing daytime water loss.[15]
A saguaro without arms is called a "spear".[16]
Some saguaros grow in rare formations called a cristate, or "crested" saguaro. This growth formation is believed to be found in one in roughly 10,000 saguaros, with 2743 known crested saguaros documented.[17] The crest formation, caused by fasciation, creates a seam of abnormal growth along the top or top of the arm of the saguaro.[18]
Ribs
Inside the saguaro, many "ribs" of wood form something like a skeleton, with the individual ribs being as long as the cactus itself and up to a few centimeters in diameter. The rib wood itself is also relatively dense, with dry ribs having a solid density around 430 kg/m3 (27 lb/cu ft), which made the ribs useful to indigenous peoples as a building material. While the ribs of dead plants are not protected by the Arizona native plant law, the Arizona Department of Agriculture has released a memo discussing when written permission is needed before harvesting them because of the importance of the decomposition of cactus remains in maintaining desert soil fertility.[19]
The composition of the ribs is similar to that of hardwoods.[20]: 326
Spines
The spines on a saguaro are extremely sharp and can grow to 7 cm (3 in) long,[7] and up to 1 mm (1⁄32 in) per day. When held up to the light or bisected, alternating light and dark bands transverse to the long axis of spines are visible. These bands have been correlated to daily growth. In columnar cacti, spines almost always grow in areoles that 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 upward. Thus, older spines are toward the base of a columnar cactus and newer spines are near the apex. Studies are underway[when?][by whom?] 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).[21]
The spines may cause significant injury to animals; one paper reported that a bighorn sheep skull had been penetrated by a saguaro spine after the sheep collided with a saguaro.[22] They can also cause severe injury to humans, being as sharp and nearly as strong as steel needles. Their long, unbarbed nature means that partially embedded spines can be easily removed, but their relative length can complicate injuries. The spines can puncture deeply, and if broken off, can leave splinters of spine deep in the tissue that can be difficult to remove. Fully embedded spikes are also difficult to remove. Such injuries do not usually result in infection, though, as the cactus spines are generally aseptic. However, spines that remain embedded may cause inflammatory granuloma.[23]
Flowers
The white, waxy flowers appear in April through June, opening well after sunset and closing in midafternoon. They continue to produce nectar after sunrise.
Pollination is considered relatively generalized in that multiple species can produce effective pollination when some populations are excluded. Main
The primary nocturnal pollinator is the
Flowers grow 8.6–12.4 cm (3.4–4.9 in) long, and are open for less than 24 hours. Since they form only at the top of the plant and the tips of branches, saguaros growing numerous branches is reproductively advantageous. Flowers open sequentially, with plants averaging four open flowers a day over a bloom period lasting a month.[7] In Southern Arizona, saguaros begin flowering around May 3 and peak on June 4.[27] A decline in bat populations causes more daytime flower openings, which favors other pollinators.[28]
Fruit
The ruby red fruits are 6 to 9 cm (2+1⁄2 to 3+1⁄2 in) long and ripen in June, each containing around 2,000 seeds, plus sweet, fleshy connective tissue.[8][29]
The fruits are often out of reach and are harvested using a pole (made of two or three saguaro ribs) 4.5 to 9 m (15 to 30 ft) long, to the end of which cross-pieces, which can be made of saguaro rib, catclaw, or creosote bush, are attached. This pole is used to hook the fruits or knock them free.[30]
Saguaro seeds are small and short-lived. Although they germinate easily, predation and lack of moisture prevent all but about 1% of seeds from successful germination. Seeds must wait 12–14 months before germination; lack of water during this period drastically reduces seedling survival. The existence of
Native American Indians of the Southwest would make bread from the ground seeds of saguaro.[32]
Genome
The saguaro genome is around 1 billion base pairs long.[33] Sequencing has revealed that the genome of the saguaro's chloroplast is the smallest known among nonparasitic flowering plants. Like several other highly specialized plant taxa, such as the carnivorous Genlisea and parasitic Cuscuta, the saguaro has lost the ndh plastid genes, which codes for production of NADPH dehydrogenase pathway, but unlike those taxa, the saguaro remains fully autotrophic; i.e. it does not eat or steal part of its food. The saguaro is remarkable for the scale and completeness of gene loss; essentially no traces of the 11 ndh genes remain in the plastid. The genes appear to have been copied to the nuclear DNA and mitochondrial DNA, but those copies are non-functional. How the saguaro thrives in a high stress environment without working copies of this fairly important gene remains unknown, but it is possible that the functions of the ndh genes have been taken on by another pathway.[34]
Taxonomy
Carnegiea gigantea is the only species in the monotypic genus Carnegiea.[7] The first description of the species was made by William H. Emory in 1848, during his surveys along the pre-Gadsden Purchase United States-Mexican border.[35] This description allowed cactus expert George Engelmann to formally name it, during his work on the United States and Mexican Boundary Survey, published in 1859.[36] The next major taxonomic treatment came from The Cactaceae, the seminal work on cactus by Nathaniel Lord Britton and Joseph Nelson Rose.[citation needed]
What tribe Carnegiea gigantea belongs to is a matter of taxonomic dispute. A molecular analysis of the cactus family in 2010 placed the saguaro in the Echinocereinae.[37] The ARS Germplasm Resources Information Network places it in the Echinocereeae.[38]
The generic name honors businessman and philanthropist
Distribution and habitat
The Saguaro is endemic to the Sonoran Desert and is found primarily in western Sonora in Mexico, and in southern and portions of western Arizona in the US. There are only 30 known wild saguaros found in southeastern California.[41] Elevation is a limiting factor to its environment, as the saguaro is sensitive to extended frost or cold temperatures.[8] No confirmed specimens of wild saguaros have been found anywhere in Nevada, New Mexico, Texas, Colorado, Utah, nor in the high deserts of northern Arizona.[42] The northern limits of their range are the Hualapai Mountains in Arizona.[7] They are the northernmost columnar cacti in the Americas.[20]: 320
Ecology
The saguaro is a keystone species, and provides food, shelter, and protection to hundreds of other species. Every stage of the saguaro's life sustains a significant number of species, from seedling to after its death.[43]
As food for wildlife
The saguaro provides voluminous amounts of pollen, nectar, and fruits.[43] The fruits are eaten by the white-winged dove and ants, so that seeds rarely escape to germinate.[44] White-winged doves are important pollinators, visiting blooms more often than any other bird species. For desert white-winged doves, 60% or more of their diet is saguaro-based. Their breeding cycle coincides with that of the saguaro blooming.[45]
Nests
Gila woodpeckers and gilded flickers create holes in the cactus to make nests, which are later used by other birds, such as elf owls, purple martins, and house finches.[46][47][48][49][50] Gilded flickers excavate larger holes higher on the stem compared to Gila woodpeckers. The resulting 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.[44]
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, tyrant flycatchers, and wrens.[51] 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.[citation needed] In 2020, a bald eagle was found nesting in a saguaro for the first time since 1937.[52][53]
Conservation
Harming or vandalizing a saguaro in any manner, such as shooting them (sometimes known as "cactus plugging")[54] 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.[55] Exceptions to this general understanding exist; for example, a private landowner whose property is 10 acres (4 hectares) or less, where the initial construction has already occurred, may remove a saguaro from the property.[56] 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.[57]
In 1982, a man was killed after damaging a saguaro. David Grundman was shooting and poking at a saguaro cactus in an effort to make it fall. An arm of the cactus, weighing 230 kg (500 lb), fell onto him, crushing him and his car. The trunk of the cactus then also fell on him.[54][58] The Austin Lounge Lizards wrote the song "Saguaro" about this death.[58]
Contrary to published statements,[59] no law mandates 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.[60]
Invasive species, such as
Climate change may threaten saguaros and their ecosystems, as deserts are particularly susceptible to climate effects. Rising daytime and nighttime temperatures will reduce the water use efficiency of saguaros, forcing them to use more water and making them more likely to die during drought periods.[15]
Uses
Ethnobotany
The utility of the saguaro is well known to
The seeds are ground into meal or eaten raw, but the raw seeds are mostly indigestible. They are also pressed for their oils. They also have minor use in the tanning of leather. In modern times, these uses have declined, and the seeds are now mainly used as chicken feed.[20]: 324
The ribs of the dead saguaro were used for construction and other purposes by Native Americans.[8] The Tohono O'odham use it for making fences and furniture. The ribs are also used as livestock fodder.[40]
A variety of alkaloids, including carnegine, gigantine, and salsolidine, make the stems quite bitter, and an unpalatable way to gain water.[20]: 323
Reports of saguaro use date back to the Coronado expeditions of 1540–1542, which noted its use in winemaking.[20]: 324
The old bird nests resist the elements and are gathered by Native Americans for use as storage vessels.[44] Cactus boots, excavated by gilded flickers and taken from dead saguaros, have been used by native peoples as water containers.[8]
The saguaro features prominently in indigenous folklore and religions.[20]: 320
Culture
Arizona made the saguaro blossom its territorial flower on March 13, 1901, and on March 16, 1931, it became the state flower.[66]
The saguaro is often used as an emblem in commercials and logos that attempt to convey a sense of the Southwest. Notably, no naturally occurring saguaros are found within 400 kilometers (250 miles) of El Paso, Texas, but the silhouette is found on the label of Old El Paso brand products.[67][42] Though the geographic anomaly has lessened in recent years,[citation needed] Western films once enthusiastically placed saguaros in the Monument Valley of Arizona (north of their native range), as well as New Mexico, Utah, and Texas.
Gallery
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Silhouette at sunset
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Saguaro towering over a 6 ft (1.8 m) man
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Mature five-armed in flower
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Snow-covered saguaro nearTucson
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Needles, Paradise Valley, Arizona
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Flowers, Scottsdale, Arizona
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The bare wooden ribs of a dead saguaro
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”Grand-daddy”, the largest saguaro ever recorded, died in the early 1990s
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Saguaro in blossom in springtime
References
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- ^ "Carnegiea gigantea (Engelm.) Britton & Rose". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved November 30, 2020.
- ^ "Carnegiea Britton & Rose". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved November 30, 2020.
- ^ "Carnegiea gigantea (Engelm.) Britton & Rose". Tropicos. Missouri Botanical Garden. Retrieved September 19, 2014.
- ^ "Definition of SAGUARO". January 14, 2024.
- ^ "Saguaro with 78 arms is named 'Shiva'". KGUN 9. June 24, 2021. Retrieved March 21, 2022.
- ^ US Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Retrieved October 2, 2019.
- ^ a b c d e f "Saguaro Cactus Fact Sheet". desertmuseum.org. Retrieved March 27, 2019.
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- ^ Brean, Henry (September 22, 2019), "Tree hunters stalk giants for Arizona's growing list of champions", tucson.com, retrieved January 30, 2020
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- ^ a b c Buckley, Steve (2011) [First published 2009]. Common Plants of Saguaro National Park (PDF). National Park Service; Sonoran Desert Network. p. 63.
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Cavities in saguaro cactuses in the Southwest are common. Both gilded flickers and Gila woodpeckers make these cavities for nesting, but they often choose different locations on the cactus.
- ^ "Gila Woodpecker". Nature Conservancy. Archived from the original on December 15, 2016. Retrieved October 28, 2011.
Although they do not use them immediately, waiting first for the sap to harden, Gila Woodpeckers excavate cavities in cacti and trees as nesting sites.
- ISBN 0811726967.
Cavities in saguaro cactuses in the Southwest are common. Both gilded flickers and Gila woodpeckers make these cavities for nesting, but they often choose different locations on the cactus. The stouter bills of the gilded flickers allow them to cut cavities through the wooden ribs near the top of the cactus where the ribs converge. Gila woodpeckers stay at midlevel on the cactus where the ribs are separated enough to cut a cavity between them. Cavities in saguaros are cut out by these birds the year before they are inhabited. The excavated cactus secretes a fluid that hardens into a scab, thus preventing water loss, which could kill the cactus, as well as waterproofing the inside of the nest cavity.
- ^ "Gila Woodpecker Fact Sheet". desertmuseum.org. Retrieved February 22, 2019.
- ^ "Gila woodpecker". Nature Conservancy. Archived from the original on May 2, 2010. Retrieved January 24, 2011.
Although they do not use them immediately, waiting first for the sap to harden, Gila woodpeckers excavate cavities in cacti and trees as nesting sites. Females typically lay two broods a year of three to five eggs, which incubate for 14 days. Once abandoned, the cavities are occupied by reptiles, rodents, and small birds like kestrels, elf owls, flycatchers, and wrens. In the desert, the woodpeckers perform the important ecological function of removing unhealthy flesh from the saguaro cactus. Some insects on which it feeds carry diseases, harmless to the bird, which damages the cactus and leaves discolorations. The marks signal larvae to the bird, and as it excavates the insects, it also cuts away the diseased tissue. As the sap hardens, the cactus is healed, and the excavation becomes a convenient nesting site.
- ^ "AZGFD spots first documented bald eagle nest in saguaro". KGUN. April 16, 2020. Retrieved April 16, 2020.
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- ^ "Arizona Revised Statutes, A.R.S. 3-904.(H): Destruction of protected plants by private landowners; notice; exception". Arizona State Legislature. Archived from the original on October 16, 2018. Retrieved December 18, 2021.
- ^ a b Mikkelson, David (February 8, 2015), Death by Saguaro, Snopes, retrieved January 20, 2017
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While damaging a cactus in Arizona will not warrant the rumored possibility of 25 years in prison, it is still considered a class four felony.
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- ^ Inc., General Mills. "Cooking Ideas from Old El Paso". oldelpaso.com. Retrieved April 24, 2018.
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Further reading
- Benson, L. (1981). The Cacti of Arizona. University of Arizona Press. ISBN 0816505098.
- Drezner TD (2005) Saguaro (Carnegiea gigantea, Cactaceae) growth rate over its American range and the link to summer precipitation. Southwest Nat 50:65–68.
- Felger, Richard; Mary B. Moser. (1985). People of the desert and sea: ethnobotany of the Seri Indians. Tucson: University of Arizona Press. ISBN 978-0816508181.