The saguaro is a large species of cactus with a tree-like structure, which can reach a height of more than 12 m. It is part of the Carnegiea genus, which is a monotypic one, and it is native to the North American continent. It grows in the Mexican State of Sonora, Arizona's Sonora Desert, as well as some areas of California such as the Whipple Mountains and Imperial County. The botanical name
comes from Andrew Carnegie. The species' flower was designated as the state wildflower of Arizona and the Saguaro National Park was established near Tucson in 1994 in order to protect it. The saguaro has the specific shape of most cacti found in the American southwest. It consists of a very tall and thick main stem, resembling a column, and a number of large branches that grow upwards. Saguaro is covered by clusters of strong spines, about two inches long, which are found all over the smooth and waxy skin of the plant. Like all cacti, saguaro has a natural ability to store water
. It can absorb up to a ton of water, storing it in the outer pulp. Water makes it expand and greatly increases the trunk's diameter, similar to an accordion. Young saguaro plants are often found in locations shaded by a larger shrub or tree. Such places are protected and more humid than exposed locations, and help with germination. It has a very slow rate of growth, with a maximum of about one inch per year. It has a long lifecycle; some saguaros are more than 200 years old and develop up to five arms. Despite the massive weight and height of saguaro cactus, its root system is not well developed. The main tap root is about three feet deep, while many smaller roots grow from its base in a radial pattern. These stout side roots are no longer than one foot. On a radius grossly equal to the plant's height, there is a network of small and shallow roots. These help anchor the great cactus by wrapping around the rocks found in the ground. The saguaro can live for more than 150 years, which is uncommon for a cactus. Some saguaros never grow any arms, for unknown reasons, and are popularly known as spears. Otherwise, it takes between 75 and 100 years for the first one to grow and the oldest plants can have 5 of them. These side arms boost the plant's production of flowers and fruits. Saguaros have a slow rate of growth, directly linked to the amount of rain. Specimens around Tucson grow twice as fast as those in the western deserts of Arizona, where the climate is drier. This cactus can only grow from seeds
, as the cuttings are not viable. It expands slowly, eventually reaching heights of over 12 meters. The Champion Saguaro in Maricopa County, Arizona, is believed to be the largest one alive, with a height of 13.8 meters and a width of 3.1 meters. However, a spear saguaro growing near Cave Creek, Arizona, was even taller, reaching an impressive 23.8 meters. It was destroyed by a powerful storm in 1986. Saguaro cactus is very well adapted to the dry desert environment. When it rains, the saguaro is able to absorb and store a massive amount of water, which it uses later during periods of drought. The diameter of the trunk and arms greatly expands in the process. The bloom starts in April and can last until June. The white flowers open late at night and close back during the afternoon, producing nectar during the entire period. Pollination is complex, due to the large number of ovules it needs a large amount of pollen in order to be complete. Cross-pollination is required, since the flowers are not self-compatible. Flowers have a large number of stamens producing pollen; one flower was found to have no less than 3482 of them. As a result, thousands of small seeds can be found in one fruit, if pollination is complete. However, the fruit will develop even if only some of the ovules are pollinated, a process known as a redundant pollination system. A variety of species contribute to pollination, such as honey bees
and other insects but also doves or bats. Honey bees and other diurnal species are usually the most important pollinators. Besides bees, many bird species pollinate the flowers during the day. These include the black-chinned hummingbird, the broad-billed hummingbird, Costa's hummingbird, Scott's oriole, the Gila woodpecker, the gilded flicker, the verdin, house finch and the hooded oriole. During the night, the lesser long-nosed bat contributes to pollination when it comes to feed on the nectar. The saguaro is specially adapted for bat pollination, this is why the flowers are open during the night, produce nectar and emit fragrances at that time. The flowers have a strong structure design to sustain the weight of bats and are located very high where other species can't reach them. In addition, it appears that bat lactation is facilitated by some amino acids found in the saguaro pollen. The saguaro fruits mature in June and have a red color, with a length between 6 and 9 cm. They are edible and very popular in the native range of the saguaro cactus. The flesh is sweet and contains more than 2000 tiny seeds. Since they are located very high, it is impossible to pick the fruits by hand. A tool is required, consisting of two poles, with a length of 2 to 5 m. Sometimes, a saguaro rib is used for this purpose. Many tribes in the area have used the saguaro fruit for a very long time. It plays a special role for the Tohono O'odham tribes, who prepare a fermented alcoholic beverage from the red fruits. They believe it can bring rain and help their crops, so it is used in the rituals that mark the start of the summer agricultural season.