—William Hornaday, upon making his first visit to the desert laboratory on Tumamoc Hill in 1907
"More amazing perhaps than any aspect of its biology is Man's emotional involvement with the saguaro—the saguaro is a 'hero' among plants. He has endowed it with human attributes and bestowed upon it affection and concern for its 'problems.'"
—Scotty Steenbergh and Charles Lowe, Ecology of the Saguaro II
The saguaro is one of the world's most studied wild plant species, probably because of its charisma and ready accessibility, but also because, as a large cactus, it is decidedly different from plants more familiar to researchers. Virtually every aspect of its life and its place in cactus evolution has been minutely examined. The essays in this book bear witness to the ongoing fascination researchers find in the great cactus, as well as the plant's unusual characteristics. There is simply no other plant like it in the United States, so instantly identifiable, so predictably located, and possessor of such a variety of distinct characteristics. It also has a national park dedicated to it, joining only the Joshua tree, the coastal redwood and the sequoia in that honor. The vast literature concerning the saguaro is testimony to its prominence as a symbol, to the perceptions it inspires, its role in human society, and its role in desert ecology.
The saguaro, with its great size and characteristic shape—its arms stretching heavenward, its silhouette often resembling a human—has become the emblem of the Sonoran Desert of southwestern Arizona. This is rightly so, for it is by far the largest and tallest cactus in the United States and our tallest desert plant as well. In this volume, we present a summary of current information about this, the desert's most noteworthy plant.
Saguaros occasionally reach 12 meters (40 feet) in height, and individuals over 15 meters (50 feet) tall appear from time to time. The record height is 23 meters (78 feet), a well-known plant of a single stalk growing near Cave Creek, Arizona, which was toppled by winds in 1986. Photos of that plant are elusive, but it was clearly a very tall cactus, perhaps the tallest of any cactus ever recorded. While other cactus species may produce individuals taller than the average saguaro, none has been documented of that stupendous height. In 1907 William Hornaday reported a saguaro between 55 and 60 feet in height. He was leader of a 1907 scientific expedition to Pinacate Volcanic Range in Mexico near the border with southwestern Arizona and was in the company of distinguished researchers. The saguaro's sole competitor for tallness in the deserts of the United States is the Joshua tree (Yucca brevifolia), a native of the Mohave Desert, a yucca that only rarely reaches 9 meters (30 feet) in height.
Saguaros are among the tallest cacti in terms of average height. They are also among those with the greatest mass. Neobuxbaumia mezcalaensis of southern Mexico, a single-stalked columnar cactus and distant relative of the saguaro, probably reaches greater average height, with individuals reaching in excess of 18 meters (60 feet). Other columnar giants include Pachycereus weberi and Mitrocereus fulviceps of southern Mexico and Pachycereus pringlei, the cardón sahueso of the Sonoran Desert in Baja California and the coastal regions and islands of central Sonora. Pachycereus pringlei and the truly massive P. weberi routinely exceed the mass of the saguaro. While columnar cacti are widespread in South America, none reaches the height or mass of the larger saguaros.
The most famous incident involving cacti of any kind occurred in 1982. The episode featured a saguaro growing near Phoenix, Arizona, and an unfortunate drunk named David Grundman, a hapless chap. Grundman, having imbibed an excess of strong drink, decided to knock over a saguaro with his jeep. He failed, succeeding only in damaging his vehicle. In a fit of rage at the unobliging saguaro, he fired both barrels of a shotgun at its base. The blast weakened the trunk, and the great plant toppled, crushing Grundman beneath. Few observers shed tears over the vandal's demise. A published ballad commemorates his folly.
Part of the allure of saguaros, attributable to their towering height, is that they are a truly tree-size cactus, the only such plant in the United States. They are unmistakable, truly incapable of being confused with any other plant growing in this country, and they lend themselves to artistic depiction like no other plant. They appear dramatically on the landscape as the visitor enters the Sonoran Desert of the United States and disappear just as suddenly beyond that desert's boundaries, except in the extreme south.
People indigenous to the Sonoran Desert region have been intimately familiar with saguaros for millennia. For many of them, especially the Tohono O'odham, it was their most important plant, providing food, drink, lumber, tools and shade. The O'odham term for saguaro is haashañ. They refer to the Slate Mountains, toward the northern edge of the O'odham Reservation as Haashañikam, or "Place where saguaros grow in abundance."
Seris, people of the coast of Sonora who are geographically close to the O'odham but linguistically and culturally distant, call the saguaro mojepe. They rely extensively on the plants for fruits and building materials. Mayos and Yaquis, whose lands lie at the southern edge of the Sonoran Desert and the saguaros' range, call it saguo, a word from which the common name seems to be derived. Sonoran historian and linguist Horacio Sobarzo notes that traditional Sonorans formerly referred to a tall man of elegant posture as a saguarón, or "big saguaro."
Spaniards arrived in the Sonoran Desert on foot and on horseback from southern Mexico, where they had already become familiar with Mexico's variety of cacti, including an impressive array of columnar cacti and had noted the important role that cacti played in pre-Columbian cultures of New Spain. They labeled any columnar cactus a cardón, or big thistle, a name still applied to a variety of columnar cacti in Latin America. Others they described as órganos, apparently for their resemblance to organ pipes, others still as candelabro, impressed by their resemblance to candelabras.
From the 16th century onward, Spanish and, later, Mexican botanists collected and classified cacti with scrupulous precision. Their work was rendered less onerous by the expertise of native botanists, who long ago had catalogued cacti according to their appearance and their usefulness. The Spaniard Francisco Hernandez, who studied the medicinal uses of plants in New Spain and published his findings in 1651, chronicled this knowledge. From the first expeditions to the Americas, Spaniards had been enchanted with cacti and transplanted large numbers of plants to gardens in Europe, where European botanists became acquainted with them. Postconquest documents from Mexico are replete with references to cacti, often referred to as nochtli, the Nahuatl (Aztec) generic term for them.
In the mid-18th century, the Swedish botanist Carl Linnaeus proposed a new order of plant and animal taxonomy that would gain worldwide acceptance, that of binomial nomenclature. His system provided a single standard of classification that crossed linguistic and ideological boundaries and imposed order on the world of botanists. Among the plant families he recognized was the Cactaceae (Cactos). And thus, when a cohort of European-trained taxonomists and plant explorers visited the landscapes of New Spain and catalogued its botanical wonders, their nomenclature was published in a form still useful to botanists. Included in their numbers was the eminent Mexican statesman Melchor Ocampo, who published a classification of cacti in 1844.
In the 1780s, King Charles III of Spain commissioned a multidisciplinary, but primarily botanical, expedition to carry out a comprehensive inventory of the riches of New Spain. The result was a 16-year project carried out between 1787 and 1803 that extended from Vancouver Island to San Francisco (still a part of the Spanish Empire) to Nicaragua. The leaders of the expeditions were the Spaniard Martin Sesse and the Mexican Jose Mariano Mocino, noted botanists whose species descriptions survive to this day. They readily imposed Linnaeus's system onto their extraordinary collection of plants. The result was a folio of incomparably fine drawings of plants. Many species' descriptions still bear the authors' designation Sessé & Moc. Their expedition (or expeditions, for there were multiple forays led by different leaders) was the most ambitious and encompassing ever launched in the Americas.
It is unclear which portions, if any, of northwest New Spain were included in the Sesse and Mocino expeditions, and so we have no record of the saguaro being catalogued. Members traveled as far north as Vancouver Island, but perhaps more for political and geographical reasons than to collect plants, and did not appear to venture far inland. A separate journey may have reached the southern limits of the saguaro's range, but no plant vouchers or records have been recorded from Sonora.
If members had traveled inland from San Francisco to Mexico City, they would almost certainly have penetrated the Sonoran Desert and traveled through forests of saguaros. Captain Juan Bautista de Anza had traveled in the opposite direction, from central Sonora to the San Francisco Bay area only a decade earlier (1775), ultimately founding the city. Anza's expedition departed from the hamlet of San Miguel de Horcasitas, Sonora, in the heart of saguaro country, and he and his expedition of about 250 people would have been intimately familiar with saguaros and their uses. A Franciscan priest, Pedro Font compiled a voluminous diary of the expedition, but paid little attention to natural history. He did record a myth related by the River Pimas (Akimel O'odham), who lived near the confluence of the Santa Cruz and Gila Rivers. He reports that the Indians spoke of a powerful figure named the Drinker, who arrived in their country.
At one time the Drinker became angry with the people and killed a great many of them and changed them into saguaros and this is why there are so many saguaros in the country. (The saguaro is a green, watery trunk of considerable height and evenly round and straight from its foot to its top, with rows of thick thorns all the way up, and usually having two or three branches formed in the same fashion, that look like arms.)
The Anza expedition passed through the Akimel O'odham and Maricopa lands in late October 1775, so they did not witness the flowering or fruiting periods, which probably would have attracted the priest's attention, if only to disparage the natives' use of saguaro wine. Ignaz Pfefferkorn, Jesuit missionary in the 1760s first at Tubutama on the Rio Altar, then at Cucurpe, on the Rio San Miguel, both in northern Sonora in areas thick with saguaros, wrote substantially on the geography of Sonora, including its plants, but had little to say about the saguaro. He pronounced it to be similar in size to the organ pipe cactus, a clear mistake on his part.
Earlier records of saguaros are mostly sketchy. By the time Spaniards arrived in Mexico's northwest for good, beginning in the 1620s, they had endured hardship, heat and many unreceptive Indians. Furthermore, they had already encountered a large variety of columnar cacti in their journeys from the landing at Veracruz, so the spiny giants were no novelty. Apart from a couple of observant Jesuit missionaries, few of the early immigrants recorded more than passing descriptions of saguaros in their notes. Sonora lay roughly 2,000 km from Mexico City, all of it on horseback or foot, and the region was (from the standpoint of Spanish or, later, Mexican interests) constantly plagued by Indian rebellions, making settled life difficult and unattractive to plant collectors, who would have to have been a hardy bunch. The remarkable plant diversity of central and southern Mexico was sufficient to absorb the work of a phalanx of botanists. The northwest was put off till later.
For explorers and agents arriving from the United States, however, saguaros were the first columnar cacti they encountered, and their impressions were noteworthy. It was not until an event of international importance that we have the earliest sustained descriptions of saguaros: reports from the Boundary Survey Commission, charged with fixing the boundary between Mexico and the United States.
In the war against Mexico, beginning in 1843, U.S. military domination forced Mexico into the Treaty of Guadalupe Hidalgo of 1848, in which Mexico ceded an enormous chunk of what is now the Southwest to the United States for about $15 million. The new U.S. territory included all of what are now Arizona and New Mexico and much of California, plus parts of Colorado, Nevada, Utah, and Wyoming. The annexed lands also included a significant portion of saguaro habitat—all those plants located north of the Gila River. John Russell Bartlett, a renowned man of letters, headed the early Boundary Survey Commission, a party dispatched by the U.S. government to determine just what the United States had got for its money and military success and to fix the border. From Bartlett's field notes, later published privately as his Personal Narrative, appeared the first widely circulated English language popular descriptions of the saguaro. While Bartlett was not specifically instructed to submit geographical descriptions to the U.S. government, he was a keen observer of nature, and his diary and drawings brought to public attention the peculiar and wondrous plant known as the saguaro and its fruits, which he referred to as petahayas.
General W. H. Emory, whose notes describing the saguaro were among the first to be circulated among botanists, succeeded Bartlett as director of the Boundary Survey Commission, perhaps in 1853. Emory had a passion for collecting specimens for scientific study, and his enthusiasm infected members of the survey team. Under his direction, they also gathered thousands of plants and pressed and shipped them for description or identification to botanists stationed at leading institutional herbaria in the eastern part of the United States. Other officials of the survey also contributed botanical collections from the Sonoran Desert region, many species of which still bear their names, such as Bigelow, Parry, Schott, Thurber, and Wright. For the cactophile (a person with unusual fondness for cacti), the most useful publication to emerge from the survey is Cactaceae of the Boundary, published in 1858 by Dr. George Engelmann, after whom the Engelmann spruce is named. A prominent botanist trained as a medical doctor who could also serve as physician for the survey team, Engelmann's taxonomy of the saguaro is sophisticated: he wrote the original species description, which to this day bears his name. His original description of the plant (Cereus giganteus), first published in 1848,10 is remarkably detailed and his ecological observations accurate and informative. The drawing of the plant included in his publication, however, is a tad romantic and vastly exaggerates the saguaro's size.
The boundaries resulting from the Treaty of Guadalupe Hidalgo did not include the portion of desert territory to the south that surveyors considered the best route for constructing a railroad connecting the eastern and southwestern United States. As a result, negotiations between the two nations began almost immediately after the signing of the Treaty of Guadalupe Hidalgo for the United States to acquire much of what is now southern New Mexico and southern Arizona—land that afforded the least mountainous and safest route for a railroad. While many Mexicans and U.S. citizens protested any further annexation of Mexican territory by the ambitious nation to the north, the Mexican government needed money and consequently agreed to sell the parcel to the United States. The transaction was completed in 1853 in a treaty known as the Gadsden Purchase in the United States and Tratado de la Mesilla in Mexico. The acquisition fixed the current border of Arizona and New Mexico with Mexico. Establishing its precise location fell to the existing boundary commission, which simply added the Gadsden Purchase to its survey package. And thus, the densest saguaro forests came to reside within the boundaries of the United States.
The construction of the southern Pacific railroad through the Sonoran Desert region, as envisioned by the promoters of the Gadsden Purchase, was completed in 1880. Almost overnight, passenger service made arrival in the desert far easier for the armed forces, land speculators, adventurers, and sufferers of asthma and tuberculosis, long before the advent of improved roads. It also opened a vast area of research for students of natural history. Scholars and scientists could board the railroad on the East Coast and arrive in southern Arizona four days later. In 1903, scientists associated with the Carnegie Institution founded the Desert Laboratory in Tucson, Arizona, an important stop along the Southern Pacific route. The laboratory was constructed on a high shoulder of a volcanic peak called Tumamoc Hill, which overlooks the Santa Cruz River (in reality, a small stream at the time, now a dry wash except for occasional ephemeral runoff) and lies only a couple of miles from the city's center. The founding purpose of the Desert Laboratory was to promote research into the relationships among plants and animals and the desert in which they lived. It seems certain that the driving force surrounding the creation of the laboratory was scientists' fascination with the saguaro, which abounds on Tumamoc Hill, and it is around this time that scholarly descriptions of the ecology of the saguaro cactus began appearing in learned journals.
No scientist could match the importance of Forrest Shreve in describing the ecology of deserts, especially the Sonoran Desert. He can be safely labeled the founder of Sonoran Desert ecology. It was he who first proposed specific boundaries to the Sonoran Desert, limits he suggested based on his own expeditions and fieldwork. Shreve moved to Tucson in 1908 to join the Desert Laboratory and used it as a base for field studies that took him to nearly every landscape in the desert Southwest, northwest Mexico, and Baja California. His first publications on the saguaro and desert ecology appeared in 1910, and he published almost continuously until his death in 1950. The first of his two-volume Vegetation and Flora of the Sonoran Desert was published posthumously in 1951. Volume 2 was completed by his collaborator Ira Wiggins and published in 1964. The work contains the results of Shreve's decades-long studies of the Sonoran Desert, its plants, and its vegetation, along with the flora of the region compiled by Wiggins. While Shreve's writing is somewhat dry and his pronouncements clinical, the saguaro emerges as the most important plant in his vast studies.
Perhaps the most important study of cacti emerged from the work of Nathanial L. Britton and Joseph N. Rose. Between 1919 and 1923, they published a magisterial four-volume, lavishly illustrated work, The Cactaceae, funded in part by the Carnegie Institution. The Desert Laboratory was influential in the volumes' scope. Many of Britton and Rose's descriptions remain intact, in spite of seemingly unending revisions, lumpings, and splittings by subsequent taxonomists.
It is also important to acknowledge the profound expansion of knowledge of Mexican cacti resulting from the work of Mexican cactologist Helia Bravo-Hollis. In 1978, Mexico's National Autonomous University published the first volume of her three-volume work Las Cactáceas de México, which she had begun in the 1930s. The third volume was published in 1991 with the assistance of the eminent Mexican cactologist Hernando Sanchez-Mejorada and remains an invaluable resource for students of cacti and of the distribution of the family in Mexico, though it has yet to be translated into English.
Since Shreve's publications, numerous scientists have published studies of the ecology, biochemistry, phenology, and biogeography of the saguaro. The plant seems an irresistible object of study from a multitude of perspectives, as this volume demonstrates.
Excerpted with permission from The Saguaro Cactus: A Natural History by David Yetman,