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Saguaro ( Carnegiea gigantea)
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Saguaro - Carnegiea gigantea
The saguaro (scientific name Carnegiea gigantea) is a large, tree-sized cactus species in the monotypic genus
Carnegiea. It is native to the Sonoran Desert in the U.S. state of Arizona, the Mexican state of
Sonora, a small part of Baja California in the San Felipe Desert and an extremely small area of
California, U.S. The saguaro blossom is the State Wildflower of Arizona.
The common name saguaro came into the English language through the Spanish
language, originating in the O'odham language.
Saguaros main habitat is Sonoran Desert, wherein the range is limited by freezing temperatures in
winter. Saguaros are also limited by elevation. They are generally found growing on rocky slopes and well drained
flats, from nearly sea level to approximately 1100 m in elevation. Saguaros growing higher than 1100 m are usually found on
south-facing slopes where freezing temperatures are less likely to occur, or are shorter in
duration. They grow slowly from seed, and not at all from cuttings. Whenever it
rains, saguaros soak up the rainwater. The cactus will visibly expand, holding in the
rainwater. It conserves the water and slowly consumes it.
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. A saguaro's growth is extremely slow. After 15 years, the saguaro may be barely a foot
tall. At about 30 years saguaros begin to flower and produce fruit. By 50 years-old the saguaro can be as tall as 2 m. After about 75 years on
average, it may sprout its first branches, or "arms". By 100 years the saguaro may have reached 7,5 m. An adult saguaro is generally considered to be about 125 years of
age. Saguaros may live at least 150 years. Giant Saguaro or more attain the grandest
sizes, towering as high as 15 m or more and weighing 10 tons, sometimes more, dwarfing every other living thing in the
desert. Saguaros rank among the largest of any cactus or desert plant in the
world. The average life span of a saguaro is at least 150 - 175 years of age.
However, biologists believe that some plants may live over 200 years.
One of the largest saguaros known to exist possessed these amazing statistics: It lived 300
years, was over 12m tall, had 45 arms, and weighed 13 tons!
The spines on saguaro having a height less than 2 meters 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 aureoles which originate at the apex of the
plant. Individual spine growth reaches mature size in the first season and then cease to
grow. Areoles are moved to the side and the apex continues to grow upwards. Thus, the older spines are towards the base of a columnar cactus and newer spines are near the
apex. Current studies are underway to examine the relationship of carbon and isotope ratios in the tissues of spines to the past climate and photosynthetic history of the
plant.
The night blooming white and yellow flowers appear April through June and the
sweet, ruby-colored fruit matures by late June.Form a cluster of creamy white petals around a dense group of yellow
stamens, on a 6-10 long tube. Though normally found at the terminal end of the main trunk and
arms, flowers may also occur down the sides of the plant. Flowers will continue to be produced throughout a saguaro's
lifetime.
The saguaro has more stamens per flower than any other cactus flower. Saguaro flowers are self incompatible thus require cross
pollination. Large quantities of pollen are required for complete pollination as there are numerous
ovules. A well-pollinated fruit will contain several thousand tiny seeds.
The major pollinators are bats, primarily the lesser long-nosed bat, feeding on the nectar from the
night-blooming flowers, which often remain open in the morning. There are a number of floral characteristics geared toward bat
pollination: nocturnal opening of the flowers, nocturnal maturation of pollen, very rich
nectar, position high above the ground, durable blooms that can withstand a bat's
weight, and fragrance emitted at night. One additional evidence is that the amino acids in the pollen appear to help sustain lactation in
bats. The flowers remain open into the daylight hours and continue to produce nectar after
sunrise. Doves and bees appear to be the primary daytime pollinators.
Unlike the Queen of the Night cactus, not all of the flowers on a single Saguaro bloom at the same
time. Instead, over a period of a month or more, only a few of the up to 200 flowers open each
night, secreting nectar into their tubes, and awaiting pollination. These flowers close about noon the following
day, never to open again. If fertilization has occurred, fruit will begin to form
immediately.
The 3-inch, oval, green fruit ripens became ryby just before the fall rainy
season,
in June, splitting open to reveal the bright-red, pulpy flesh which all desert creatures seem to
relish. This fruit was an especially important food source to Native Americans
(O'odham tribes) of the region who used the flesh, seeds and juice. Seeds from the Saguaro fruit are prolific -- as many as 4,000 to a single fruit -- probably the largest number per flower of any desert
cactus. One saguaro produces tens of thousands of seeds in a year, and as many as 40 million in a lifetime of 175 to 200
years, but out of all the seeds that a saguaro produces in a lifetime, few will survive to
adulthood.
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.
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, Arizona.
The Seri people of northwestern Mexico used the plant which they call mojepe for a number of
purposes.
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 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. 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. To point this out the Texas rockabilly band the Reverend Horton Heat has a song
"Ain't No Saguaro In Texas".
Source:
http://en.wikipedia.org/wiki/Saguaro
http://www.cactus-art.biz/schede/CARNEGIA/Carnegia_gigantea/
Carnegia_gigantea/carnegia_gigantea.htm
http://www.desertusa.com/july96/du_saguaro.html
