Saguaro National Park
Blasted and bewitching, the Sonoran desert of Mexico and the American Southwest has long stirred the imagination. Perhaps it is because, amid its arid plains and rocky arroyos, this dry, rugged land seems so indifferent to the needs of human life. Perhaps, too, it is the landscape's very harshness, its ceaseless challenge to the ingenuity of all living things, that so attracts us. And perhaps it is the cactus.
Certainly no plant is so closely linked to the desert Southwest as the giant saguaro, the second largest of 2,000 known species of cacti. (It is surpassed only by the cardon cactus of southern Mexico.) Oddly human in form, the saguaro has plump green arms that, outstretched and uplifted, seem to wave, although whether in greeting or warning, it is hard to say. And, unless you travel to Sonora, Mexico, nowhere else on Earth will you find a more stately assemblage of the prickly giants than here, in Saguaro National Park.
Saguaro East
Bracketing booming Tucson to the east and west, Saguaro National Park consists of two separate units: Saguaro East and Saguaro West. Saguaro East, also known as the Rincon Mountain District, is the larger of the two. Its 104 square miles include not only the great forests of aging saguaros but also the high-country wilderness of the Rincon Range, a majestic, brooding presence that looms to the east.
As you enter the district from Tucson, you encounter a landscape of awesome bleakness: an arid, rolling plain of boulders and sand, dry washes and arroyos, slender canyons and fan-shaped bajadas. The climate is undeniably harsh; in winter the temperature may dip into the 40s, but summertime highs routinely top 100ºF, and months may pass without a drop of rain. (The desert receives, on average, just 12 inches of rain per year, most of it in the fall and winter, when violent downpours can quickly fill arroyos and create dangerous flash floods.)
Untamable as it may appear, however, this is the land that the saguaro loves. And the saguaros of the Rincon Mountain District are some of the oldest and largest in the world. Reaching heights of 50 feet, the largest of these giants weigh in at eight tons. A great deal of its mass is actually water, as the saguaro is, in effect, a living storage tank. By means of a system of shallow roots that form a kind of catch-basin, it can collect as much as 200 gallons of water in a single downpour. This moisture is then stored in the spongy flesh of the cactus's limbs and trunk. Accordionlike pleats expand and contract according to the amount of water the plant has stored; the fatter a saguaro's limbs and trunk, the more water it contains inside.
The giant saguaros of the Rincon Mountain District are even more remarkable when you consider the odds against their existence. Although a single saguaro produces some 40 million seeds in its lifetime, perhaps one will take hold and grow to maturity. The lucky survivors are generally those that sprout in the shadow of a "nurse tree," such as a paloverde or a mesquite, which shades the young plant from the summer sun, protects it during winter cold spells, and conceals it from grazers.
Growth is slow and hard-won; a 10-year-old plant may be no taller than an inch. Those that survive the first decade of life grow roughly a foot every 15 years, mostly in spurts that closely follow the rhythms of seasonal rainfall. Thirty years pass before the plant produces its first flower; 75 years, before its first branches appear. Not until a century has come and gone does the plant reach a height of 25 feet and assume its familiar waving profile.
Even the most established of saguaros remain vulnerable. If the temperature dips below the freezing point for 36 hours, many will succumb to the cold. Lightning is another threat: it strikes and kills many of the oldest, tallest specimens.
Standing apart from others of its kind, the saquaro may seem to be nature's ultimate loner, a solitary survivor superbly adapted to the extreme conditions of desert life. But look more closely and you will see that the saguaro does not dwell alone. It is frequently described as a living apartment complex, since at every level there is evidence that the saguaro nurtures its fellow desert residents. Gila woodpeckers and gilded flickers carve nest holes in its trunk and branches; providing cool shade in summer and insulated warmth in winter, these cavities, when abandoned, are soon adopted by other birds, including screech owls, purple martins, and sparrow hawks, and by insects, such as honeybees.
The cactus's flowers, trumpet-shaped blossoms that appear on spring evenings and fade by the following afternoon, produce juicy red fruits that are relished by coyotes, foxes, and a number of other desert mammals. Humans, too, have put the saguaro to use. For centuries, local Indians have gathered the fruits to make wine, jams, and jellies, and have harvested the long ribs of the plant's skeleton for both fuel and building material.
Looking west
As indomitable as they appear, the saguaros of the Rincon Mountain District were once thought to be endangered. Poaching, grazing, urban growth, and old age had all taken their toll, and so the area now known as Saguaro West or the Tucson Mountain District was set aside to safeguard this living treasure. Saguaro West is considerably smaller than Saguaro East, at 34 square miles, just one third its size. Nestled against the Tucson Mountains, its dimensions are tidier, more manageable, perhaps, for the casual observer. (An air-conditioned visitor center with a shaded terrace makes it possible to survey the landscape without so much as setting foot on the desert floor.) The saguaros here are younger, not the aged titans that are found in Saguaro East but 100-year-old youngsters, marching in prickly profusion across the dusty bajadas and sun-seared hillsides.
Smaller and younger though it may be, Saguaro West is every bit as compelling as its larger partner to the east. The desert is the desert, after all, wild and untamable, a realm where nature's will, not human resourcefulness, is in command. And in the last analysis, perhaps this is the message of the saguaro, in whose upraised arms one may see not a wave of welcome or warning but of stoic triumph: we're here to stay.