President Teddy Roosevelt, the quintessential conservationist, said, “A grove of giant redwoods or sequoias should be kept just as we keep a great or beautiful cathedral.” Each time I am in Tucson, Ariz., I have been able to fully appreciate his point, but not for a typical tree like a redwood, oak, or sequoia. Instead, the superstar of Tucson and the Sonoran Desert is the saguaro cactus.
A stand of upright plants with few limbs and no leaves dominating a mountainside at sunrise is inspiring. At a certain distance from such a stand, an observer might wonder why we should preserve a landscape of telephone poles. But the close-up view is awesome, and the plant itself has qualities as singular as those of the redwoods. Both represent their state symbolically. Redwoods are the state tree of California. Saguaro enjoys recognition as the state flower of Arizona.
The saguaro cactus is the largest member of the cactus family in North America and is the only species in its genus. This means there is no other species that is closely related or that can be confused with this spectacular plant. The impressive green giants of the Sonoran Desert seem to be respected by all the residents. No one would dream of using a saguaro cactus for target practice or harming one of the plants in any way. A gun would more likely be used against someone who violated the sanctity of the saguaro cactus.
Like many Arizonians, saguaro cacti are also armed. Many have one or two, some three or more, horizontal “arms,” which then grow vertically to create the classic captured-bandit pose. But the majority simply stand upright with no arms because it takes as many as 50-75 years to grow the first one. Plants grow slowly in a desert. According to the National Park Service, “a saguaro grows between 1 and 1.5 inches in the first eight years of its life” and takes at least 35 years to reach maturity. A 50-foot-tall adult saguaro might be approaching 3 feet in diameter, weigh 6 tons and be 125 years old. The oldest ones, estimated to be more than 200, would have germinated almost a century before Arizona was a state.
In much of the Sonoran Desert habitat, saguaro cacti are the dominant plant, towering above mesquite trees, agaves and barrel cacti. The saguaro cactus has a critical role in the desert community. Gila woodpeckers and gilded flickers interact with the cactus, the only tall “tree” to be found, in the manner other woodpeckers do with a pine tree. They look for insects and excavate holes for their nests. Other birds, including elf owls, the world’s smallest raptors, also make their nests in holes in the cactus. Harris hawks sometimes nest on saguaros with arms.
Saguaro typically bloom at night, hence one of their chief pollinators are bats. Of course, the bats are not being altruistic and simply helping out the cactus. The nectar of the saguaro cactus is very rich in proteins, and one scientific study found that the amino acids associated with the cactus pollen have a positive effect on lactation in some bat species. Because most of the flowers are closed up during the day, the nectar is not depleted by diurnal birds and insects and is available as a valuable nutrient source for the bats.
At 10-year intervals a census is taken of the number, sizes, and ages of saguaro in Saguaro National Park near Tucson. The census is always in the same year as the U.S. Census. Since saguaro cacti do not move around and have no political agenda, a cactus population census is more reliable than a census of humans. In the previous estimate, in 2010, 1.6 million saguaro lived in the national park. The rough estimate for the 2020 census is that the numbers have increased to more than 2 million. As President Roosevelt recommended, we should strive to keep these icons of the desert as we do redwoods and sequoias.
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