While traveling, one often comes across sights that seem ordinary to locals, but are exotic to the visitor. Take for example the giant Saguaro cacti that I saw while passing through Arizona. I became fascinated by these amazing plants when I was able to examine them up close instead of driving by at 60 mph. Not that they are unimpressive from afar, as thousands are seen rising up from the desert floor, arms welcoming curious sightseers.
I think what intrigues me the most is their structure- How can a plant that is over 50 ft high, composed mostly of water (Large saguaros can contain as much as 8-12 tons of water), with shallow roots, remain upright for over 100 years? I had to know, so I read a couple of books from local libraries in the past few months and found some answers. The main source was by David Yetman called, “The Great Cacti, Ethnobotany and Biogeography”. This guy really, really loves Cacti!!
My curiosity started when I was camped at Pinal County West Park in Maricopa, Arizona. As I walked the trail through the park, I saw many of these giants in various degrees of decay and death. I saw their “guts” so to speak.
The Carnegiea giantea is the only columnar cactus species found in the U.S. and grows primarily in southern Arizona. It grows at a rate of 1 foot every 15 years and its branches or arms appear only after 70 years. They grow in altitudes from sea level to above 10,000 feet and are typically found on rocky slopes on the south side of mountains.
Because of their extreme height and weight (sometimes weighing over 12 tons), and shallow root systems, they are susceptible to damage from high winds and lightning strikes. Scientists postulate that lightning strikes account for the main mechanical reason for the death of these magnificent plants. Other reasons are freezing temperatures and bacterial invasion. It is hard to determine the exact cause of death, because saguaros will remain standing, languishing for many years before turning brown, shedding their flesh, and eventually falling down. Exposure to temperatures of 15 degrees F for just 1 hour will kill a Saguaro, but they can tolerate temperatures of 147 degrees F for 1 hour before rapid cell death occurs.
Cacti have evolved over millennia to adapt to harsh dry climates. Most have eliminated leaves to save from water evaporation. Succulent stems serve as water storage reservoirs, and the waxy outer skin and special metabolism help the endure the heat and dryness. Spines help insulate the plants by lowering the temperature and protect from UV radiation as well as mitigate the effect of drying winds. More than one desert lover, camped near a Saguaro swear they’ve heard music when the the wind blows through the spines!
The roots are shallow, no more than a few centimeters below the surface, but can stretch for over 30 feet in every direction. Roots drink up literally “tons” of water during rainstorms. This water can be stored for 1-2 years in the flesh of the cactus. “Rain roots” often develop after rainstorms. These are deciduous roots that shrivel up and drop off when no longer needed.
Almost every part of the Saguaro is used by desert creatures including humans. Bats and doves sip nectar from the white, night-blooming flowers. Foxes and coyotes eat the red fruit in the summer and ants shuttle away the tiny black seeds once the fruit falls to the ground. Woodpeckers and Flickers peck holes in the fleshy stem, then after a thick callus forms, a hollow “boot” is left, which is appropriated by other birds, such as the tiny Elf Owl.
Ribs that remain after the death of the giant are used as essential building materials for humans to make Ramadas ( roofed, open-sided structures that provide shade), and cross pieces for walls and roofs of native dwellings.
Many people have tried to transplant mature Saguaros, but fail, especially if the plants have multiple arms (which indicates that they are over 70 years old). Despite the fact that these cacti have evolved to overcome the rigors of their hostile environment, they can still be overwhelmed by the casual cruelty of nature and humankind.
As I wander the country with eyes wide open to the curiosities of this great land, I hope to inspire others to look more deeply into their own natural surroundings. And remember, to always “Go with the Flo”