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The Cacti: A Thorny Feast

Desert Food Chain The Cactus - Part 3


Given their spiny weaponry and heavy waxy coats, it would seem that the cacti of our Southwestern deserts have raised unbreachable defenses against foragers.  In fact, however, the cacti fulfill their role as producers in the food chain by setting a veritable banquet table for a number of animals, including the species we call “homo sapiens.” 

A Prickly Family

Cacti, with the family name of Cactaceae, first arose, in the New World, some tens of thousand of years ago.  Evolutionary newcomers to the botanical kingdom, they evoke a sense of the non-traditional or the modernist.  They could have sprung from the canvas of the famed 20th century Mexican artist and muralist Diego Rivera. 

“They are, without doubt,” said authority Clark Champie in his Cacti and Succulents of El Paso, “the oddest of the oddballs of the plant kingdom to the unending delight of the cactus fancier and utter despair of the plant classifier.  In no other plant family do the members play more tricks on the taxonomists as in this one.  For instance, some plant classifiers…insist that the number of genera [groups of species within a family] should run in the neighborhood of 20 to 25…  …other taxonomists think it might take as many as 150 genera to bring order to this unruly group of plants…  And the agreement on the number of species is no closer, with the conservatives thinking that something like 800 might do the job while those of a more liberal bent would like to the number of names running closer to 1800.” 

Our cacti here in the Southwest vary wildly in shape, size and bloom.  They occur, for instance, in the form of buttons, balls, barrels, globules, branching pads, branching stems, branching trees and towering columns.  They range in size from the humble thimble plains cactus, which measures perhaps an inch and a half in height and an inch in diameter, to the stately saguaro, which may reach more than 60 feet in height and two to three feet in diameter.  A representative of the smaller species weighs no more than a few ounces.  A large saguaro, by comparison, may weigh 10 tons or more.  Most of our cacti bloom from early spring into the fall, producing flowers in a rainbow of colors that bejewel the desert.  The blossoms range in size from a fraction of an inch to several inches in diameter. 

While we think of cacti as progeny of the desert, they “can be found in jungles, on high cold mountains, bare or grassy plains, along seashores, in sub-tropical areas, as well as in arid and semi-arid regions,” as W. Hubert Earle said in his Cacti of the Southwest.  They have extended their range across much of the Caribbean and the North and South American continents. 

Their variability notwithstanding, the cacti share certain defining characteristics that equip them for surviving desert drought.  They have thick, hard, succulent and wax-coated green stems that harbor water. 

The stems swell and shrink – a botanical camel’s hump – reflecting the store of water in the tissues.  Unlike any other plant family, the cacti stems bear circular- or oval-shaped organs called areoles from which spines grow, flowers blossom and new stems branch.  The areoles wind in perfectly arranged spiral rows around some species.  They crown phalanxes of conical-shaped tubercles in other species.  They march, in orderly pattern, along the edges of the ribs of barrel and columnar cacti.  They fall in regular columns along the edges and on the flat surfaces of prickly pear pads. 

The spines, actually modified leaves, minimize water evaporation and discourage some animals’ foraging.  The spines, according to Earle, can be porrect [extended horizontally], curved, hooked, round, stiff, acicular [needle-shaped], papery, feather-like, hair-like or sheathed.  The ironically-named teddy bear cholla, for instance, with its bristling spines, ranks as the porcupine of the plant world.  The senita, or old man, cactus, with its long wispy spines, suggests an elderly gentleman with flowing white hair and beard. 

Generally, cacti root systems spread radially near the surface, first in line for any rainfall, serving as an extensive network of conduits for conducting water to the stems.  Within hours after a rainfall, the roots “produce great number of tiny rootlets which quickly gather water and send it to the fleshy reservoirs of the plant,” according to George Olin in House in the Sun: A Natural History of the Sonoran Desert.

Unlike most of the families within the plant kingdom, cacti have perfected a biochemical method for gathering carbon dioxide – a compound integral to the daytime business of photosynthesis – during the cool of the night rather than under the heat of desert sunlight.  “Normal” plants open their stomata, or the pores in their leaves, during the day to “inhale” carbon dioxide, incorporating it immediately in the solar-energy-fueled process of photosynthesis.  This makes sense, especially given the modern notion of “just-in-time” deliveries of raw materials to factories, but it proves costly in terms of the water that escapes through the plants’ stomata.  Cacti, by contrast, open their stomata, or pores in their stems, during the night to gather carbon dioxide, converting it into an organic acid and effectively holding it in short-term storage.  When the sun rises and the heat climbs, the cacti batten down their stomata hatches.  They free the carbon dioxide from the organic acid internally as needed for photosynthesis during the day.  This extra step in the process of photosynthesis impedes efficiency – and in fact, as a result, cacti may grow more slowly than other plants – but it saves water, which can equal as much as 80 percent of a plant’s total weight.  A fair tradeoff in the desert.

Family Members

In our Southwestern deserts, the Cactaceae family includes an array of clans, or genera, that encompass variously defined species, often reflecting classifiers’ conservative or liberal biases.  The better-known genera include, for a few examples, the pincushion (Mammilaria), the hedgehog (Echinocereus), the barrel (Ferocactus and Echinocactus), the columnar (Giant Columnar), and the cholla and the prickly pear (Opuntia).

The roughly cylindrical-shaped pincushion cacti comprise perhaps several dozen species in the deserts of the Southwest.  A diminutive upright plant, they measure only a few inches in height.  The stems come adorned with long spiraling rows of tubercles tipped with areoles that give rise to a dense cloak of spines, the central ones taking the shape of a fishhook in some species.  Some pincushions grow as solitary plants, others, in dense clusters.  They bloom from early summer into the fall, producing a small club-shaped reddish fruit.  They take their name from the mammalian mammary gland because some of them produce a milky sap. 

The cylindrical-shaped hedgehog cacti includes several dozen species.  Also a small upright plant, they may grow from a few inches up to a foot in height.  Unlike their pincushion bretheren, the hedgehog cacti have stems with ribs instead of spiraling rows of tubercles.  Their areoles, located along the edges of the ribs, have needlelike (never hooked) spines.  They typically grow in clusters of several dozen stems.  Most bloom in the spring, producing a dazzling flower and a large tasty light tan or green to reddish fruit.  According to Earle, the hedgehog cacti had the named conferred by Europeans who thought that the spiny little plants resembled the bristly hedgehogs of the Old World’s hedgerows. 

The barrel cacti, including perhaps one to two dozen species in the Southwest, typically have barrel shapes and pleated, or ribbed, stems.  They measure a few inches to several feet in height.  Their areoles, located along the edges of the pleats, have distinctive, sometimes hooked, spines surrounded by radial spines.  They may grow as solitary or clumped plants.  Depending on the species, they bloom from mid-spring through the fall.  They produce yellowish green to reddish fleshy fruits that may be scaled.

The Sonoran Desert’s showy columnar cacti, all with pleated stems, include, for instance, the organ pipe, the senita, and that most spectacular of all the cacti, the giant saguaro. 

The typical organ pipe, found most prominently in southern Arizona’s Organ Pipe Cactus National Monument, rises in clusters of stems 20 feet tall.  The areoles, at the edges of the pleats, have brown to grayish, black-tipped needle-like spines.  The organ pipe blooms through the summer, and it produces a globular, reddish and sweet fruit. 

The senita, a long-lived member of the family, also rises in clusters of stems, typically reaching perhaps 10 or 12 feet in height.  Its areoles have two or three central spines surrounded by several radial spines.  It blooms at night, from spring into summer, with several flowers, foul smelling, appearing from the same areole.  It produces a small red juicy fruit. 

The saguaro, the monarch of the cacti family, often rises as a single column for 50 to 100 years.  It will then begin to grow arms, which curve upward as they mature.  The plant may live for two centuries, growing to as much as 60 feet in height.  Its areoles produce hard spines up to some eight feet on the stem and flexible spines above eight feet.  The saguaro blooms in early summer and produces a red juicy fruit. 

The bristling chollas and the iconic prickly pears, among the most common of the cacti in our Southwestern deserts, bear a kind of tribal relationship.  Both of them branch segment by jointed segment, stems from stems for the chollas and pads from pads for the prickly pears. The segments break off easily and can take root independently, producing new plants.  The cholla segments may be transported from place to place in the coats of animals.  Some chollas and the prickly pears come armed with large spines surrounded by minute barbed spines called glochids, which can cause a fiery irritation if imbedded in the skin.  They bloom from spring well into summer, with some species yielding large juicy fruits. 

A Cacti Feast

In spite of their armament, the cacti family plays an important role in the food chain of the desert. 

The pincushion species typically produce minuscule, club-shaped reddish fruits, called chilitos, that can be eaten, provided the consumer in prepared to invest considerable work in the harvest for a minimal return in nutrition.  More importantly, perhaps, some pincushion species’ tissue serves as a medicine that curanderos (Mexican healers) use to cure ear aches.  Some species, too, yield hallucinogens that induce visions among shamans, that is, those with the power to commune with the spirit world.  The pincushion’s hallucinogens can also drive you quite mad. 

The hedgehog cacti’s colorful and flaring blooms beckon in particular to the insects and the hummingbirds.  Their juicy fruits, which in one species tastes like strawberries, draw birds, rodents and humans to the table.  The stems, de-thorned and roasted or baked, appeared on the menus of early settlers.  Especially during droughts, the flesh of the hedgehog attracts rodents and blacktail jackrabbits. 

The barrel cacti fruits provide nourishment to birds, rodents, javelina, mule deer and bighorn sheep, and the plant stem itself, to cactus beetles, rodents and the javelina.  While it is true, as legend suggests, that the barrel cacti tissues contain a reservoir of water, it is not true that the plants give up their store easily to a desperately thirsty desert traveler.  In fact, they guard their water with a thick and tough skin, the botanical equivalent of a rhino hide.  They hold it in a merely damp mucilaginous pulp that, once ingested, might give you a severe case of diarrhea.  It just works out better if you carry water and take emergency precautions during adventures in the desert. 

Among the columnar species, the typically dark-red or purple tennis-ball size organ pipe fruit, called pitayas, rank near the top of the tastiest in the cactus family.  They draw insects, birds, reptiles and mammals.  Widely sold in the mercados, or marketplaces, of northwestern Mexico, the pitayas become an ingredient in  jams, jellies and beverages. 

As discovered only recently by scientists, the night-blooming senita cactus shares what botanists call a “mutualistic” relationship with a night-active moth.  The senita receives pollination services from the moth, which lays its eggs in the plant’s flowers.  The plant then produces fruit for the larvae, which dine in a spiny horn of plenty until they form pupae that will hatch into adult moths.  The cycle then begins anew, continuing what is only the third known such highly specialized plant/insect relationship in the world. 

The giant saguaro, pollinated by insects, birds and bats, produces an abundant moist fruit banquet for white-winged dove, Gila woodpeckers, house finches and other creatures, even in the midst of severe droughts.  The birds scatter the seeds, which often take root under the trees that serve as perches.  The saguaro seedlings, in a precarious beginning to life, frequently become meals for birds, rodents and jackrabbits.  From prehistoric times until the present day, the saguaro fruit has been taken in a celebratory harvest during June and July by the Tohono O’odham, an ancient tribe of Native Americans, who use the pulp and seeds to make soups, jam, candy and a potent wine. 

Of all the cacti, it is probably the cholla and prickly pears that serve up the main course in our thorny feast in the desert food chain.  Their blooms attract bees that harvest the pollen (and pollinate the plants) to feed their larvae.  Their juicy fruits draw insects, birds, reptiles and mammals.  In spite of the spines, the tissues of their stems provide meals for packrats, jackrabbits and javelinas.  In fact, prickly pears provide half the leather-snouted javelinas’ diet in some parts of the Southwest. 

More than any of the other cacti, the Opuntias have served the human diet.  According to the Arizona-Sonoran Desert Museum web site (one my sources for this article), “The formidable flower buds of some chollas are eaten by O’odham and other desert dwelling peoples.  The buds are rolled on the ground or another hard surface with sticks to remove the spines and glochids.  The buds are pit-roasted for a day, and either eaten immediately or dried and pickled for later consumption.  Cholla buds contain significant protein, but they are probably more important for their high calcium content and soluble fiber.”  Once the thorns are removed, the fruits can be eaten fresh, or they can be used to prepare various drinks, syrups and jellies.  The fruits of some prickly pears are cultivated for the marketplace. 

In Mexico, in particular, young and tender pads (called nopalitos) of the edible prickly pears (nopales) hold a major place in the diet of many people, according to the Arizona-Sonoran Desert Museum.   Once cooked, the pads become “mucilaginous like okra, and good for thickening broths.  The mucilage also helps control blood-sugar levels associated with adult-onset diabetes…  There is also clinical evidence that nopales reduce blood cholesterol.  Widely ignored by Anglos, who often regard them as worthless nuisances, opuntias are abundant and healthy foods for those who know how to use them.”

A Symbol of the Desert

While the cacti play out roles in the food chain of the desert, they also have also taken root in the prehistoric and historic human psyche as an emblematic presence of the Southwest. 

For example, the Hopis made the prickly pear a part of their oral history, recorded by J. Walter Fewkes, famed early 20th century archaeologist with the Smithsonian Institution, and published by George Wharton James in his 1912 book, The Grand Canyon Of Arizona: How To See It.  “Some of our people traveled to the North,” the Hopis told Fewkes, “but the cold drove them back, and after many days they returned.  The mothers, carrying their children on their backs, went out to gather seeds for food, and they plucked the prickly pears and gave it to their children to still their cries, and these have ever since been called the Prickly Pear People.”

In another example, adventurers who traveled across the Southwest saw the cacti as a fearsome enemy.  James Ohio Pattie, in his 1831 The Personal Narrative of James O. Pattie, of Kentucky (republished by Peter Wild in The Desert Reader) spoke of his experience during a torturous trip across the western Sonoran Desert.  “The prickly pears were in such abundance, that we were often, dazzled as our eyes were with the sun’s brightness, puzzled to find a path so as neither to torment our feet or our bodies with the thorns of these hated natives of the burning sands.”

In still another example, John C. Van Dyke spoke of the saguaro from an artistic point of view in his 1901 book The Desert (republished by Wild in The Desert Reader).  “On the mountains and the mesas,” wrote Van Dyke, “the sahuaro [sic] is so common that perhaps we overlook its beauty of form; yet its lines are sinuous as those of a Moslem minaret, its flutings as perfect as those of a Doric column.  Often and often you see it standing on a ledge of some rocky peak, like the long shaft of a ruined temple on a Greek headland.”

Next The Yuccas

By Jay W. Sharp

Prickly Pear Sweets & Treats

There has been medical interest in the Prickly Pear plant. Some studies have shown that the pectin contained in the Prickly Pear pulp lowers levels of "bad" cholesterol while leaving "good" cholesterol levels unchanged. Another study found that the fibrous pectin in the fruit may lowers diabetics' need for insulin. There are on going studies and at this point there are no proven results on humans. You can make your own study and see if works for you, which is the only test that really counts. More...


Part 1 Desert Food chain - Introduction
Part 2 Desert Food chain - The Producers
Part 3 Desert Food chain - The Cacti: A Thorny Feast 
Part 4 Desert Food chain - The Yuccas
Part 5 Desert Food chain - The Agave
Part 6 Desert Food chain - Desert Grasslands
Part 7 Desert Food chain - Desert Shrubs
Part 8 Desert Food chain - The annual forbs
Part 9 Desert Food chain - Mavericks of the Desert Plant
Part 10 Desert Food chain - Outlaw desert plants
Part 11 Desert Food chain - Animals: The Consumers
Part 12 Desest Food chain - The Insects
Part 13 Desest Food chain - The Ugly, the Uglier and the Ugliest

Also see: The Desert Food Chain for the young student




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