Saguaro cacti are the superstars of the Sonoran Desert
President Teddy Roosevelt, the quintessential conservationist, said, “A grove of giant sequoias or sequoias should be preserved just as we keep a great and beautiful cathedral.”
While in Tucson, Arizona, I was recently able to fully appreciate her sentiment. But not because of the redwoods or redwoods or any other trees. The superstar of the Sonoran Desert is the saguaro cactus.
From a distance, an observer could be forgiven for wondering why someone planted a line of slightly misshapen telephone poles. Upon closer inspection, the poles are revealed to be the stems and arms of saguaro cacti.
These erect plants with only a few limbs and no leaves dominate the landscape, and a close view is equally impressive. The plant itself has qualities as singular as those of the redwood, and each symbolically represents its state. The redwood is California’s state tree. The saguaro flower is the state flower of Arizona.
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The largest member of the cactus family in North America, the saguaro cactus is the only species of its genus. No other species is closely related to this spectacular plant.
Human residents respect these impressive green giants of the Sonoran Desert. No one I’ve met would think of using one for target practice or hurting a saguaro cactus in any way. A gun would be more likely to be turned on someone who violated the saguaro’s sanctity.
Like Arizonans, saguaro cacti can be armed. Many have one or two horizontal arms that bend and then grow vertically to create the classic captured bandit pose. Some may have three or more arms.
The majority simply stand upright without arms as it takes 50 to 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.” It takes at least 35 years to mature.
A 50-foot-tall adult saguaro can approach 3 feet in diameter, weigh 6 tons, and be 125 years old. The oldest, estimated to be over 200 years old, would have germinated nearly a century before Arizona became a state.
In much of the Sonoran Desert habitat, saguaro cacti are the dominant plant, towering over mesquites, agaves, and barrel cacti. The saguaro cactus plays a vital role in the desert community. Gila Peaks and Golden Sparkles interact with cacti, the tallest vegetation in the vicinity, as other peaks do with pine trees. They search for insects and dig holes for their nests.
Other birds, including elven owls, the smallest raptors in the world, also make their nests in cactus holes. Harris hawks sometimes nest on arm saguaros.
Saguaros usually flower at night and bats are one of their main pollinators. Of course, bats don’t help cacti just to be altruistic. Saguaro cactus nectar is quite high in protein. A scientific study has revealed that the amino acids associated with cactus pollen have a positive effect on lactation in certain species of bats.
Because most flowers are closed during the day, the nectar is not depleted by diurnal birds and insects, meaning it is available as a valuable nutrient source for bats.
At Saguaro National Park in southern Arizona, a decennial census calculates the number of saguaro cacti present, as well as the size and age of resident plants. The census takes place in the same year as the US census.
Since saguaro cacti do not roam and have no political agenda, a census of the cactus population is more accurate than a census of humans. In the previous estimate (2010), 1.6 million saguaro lived in the national park. The ballpark estimate for the 2020 census is that the numbers have risen to over 2 million.
I’m sure President Roosevelt would want us to protect these desert icons just as we do redwoods and redwoods.
Whit Gibbons is a professor of zoology and senior biologist at the Savannah River Ecology Laboratory at the University of Georgia. If you have an environmental question or comment, email firstname.lastname@example.org.