Prosopis pubescens, Prosopis velutina, Prosopis glandulosa
During the inevitable droughts and deprivations of desert frontier days, mesquite trees served up the primary food source for caravans and settlers. Mesquite beans became “manna from heaven” for the suffering men of the 1841 Texas Santa Fe Expedition said George W. Kendall (quoted by Ken E. Rogers in The Magnificent Mesquite) in his journal. “When our provisions and coffee ran out, the men ate [mesquite beans] in immense quantities, and roasted or boiled them!” During the Civil War, when groceries often ran short, mesquite beans served as passable coffee. Mesquite blooms, pollinated by bees, yield a connoisseur’s honey.
Mesquite is the most common shrub/small tree of the desert southwest. Like many members of the legume family (called Fabaceae these days), mesquite restores nitrogen to the soil. There are three common species of mesquite: honey mesquite (Prosopis glandulosa), screwbean mesquite (Prosopis pubescens ) and velvet mesquite (Prosopis velutina).
Mesquite beans, durable enough for years of storage, became the livestock feed of choice when pastureland grasses failed due to drought or overgrazing. They were carried by early freighters, who fed the beans to their draft animals, especially in Mexico.
Although often crooked in shape, mesquite tree branches, stable and durable, filled the need for wood during the construction of Spanish missions, colonial haciendas, ranch houses and fencing. Its wood served artisans in the crafting of furniture, flooring, paneling and sculpture. “Of the tree mesquite,” said Dobie, “there is one kind of yellowish wood and another of a deep reddish hue as beautiful when polished as the richest mahogany.” In some areas, mesquites provide a bountiful harvest of wood for use in fireplaces and barbecue grills.
Mesquites, requiring little water and only low maintenance, have found a place in Southwest xeriscaped gardens and parks. They not only produce beans and blooms that attract wildlife, they provide perches and nesting sites for birds, including hummingbirds.
In the frontier days, according to Dobie, mesquites were used by the Indians and the settlers as a source of many remedies for a host of ailments. Indians and settlers believed tea made from the mesquite root or bark cured diarrhea. Boiled mesquite roots yielded a soothing balm that cured colic and healed flesh wounds. Mesquite leaves, crushed and mixed with water and urine, cured headaches. Mesquite gum preparations soothed ailing eyes, eased a sore throat, cleared up dysentery and relieved headaches.
(Note: Medical studies of mesquite and other desert foods say that despite its sweetness, mesquite flour (made by grinding whole pods) "is extremely effective in controlling blood sugar levels" in people with diabetes. The sweetness comes from fructose, which the body can process without insulin. In addition, soluble fibers, such as galactomannin gum, in the seeds and pods slow absorption of nutrients, resulting in a flattened blood sugar curve, unlike the peaks that follow consumption of wheat flour, corn meal and other common staples. "The gel-forming fiber allows foods to be slowly digested and absorbed over a four- to six-hour period, rather than in one or two hours, which produces a rapid rise in blood sugar.")
Getting Acquainted with Mesquite
Mesquites, including the three species in our southwestern deserts, belong to the legume family, which ranks near the top of plants especially adapted to an arid environment. Typically, the legumes, which have woody stems and branches, produce bipinnately compound leaves (leaves with two or more secondary veins, each with two rows of leaflets). They bear flowers that have five petals, then produce abundant large seedpods that serve as a nutritious food source for wildlife. Mesquites grow wide-spreading and deep-reaching root systems that host colonies of bacteria that can fix nitrogen, one of the minerals most important to plant germination and growth.
The three species of mesquites, which include the honey mesquite, the velvet mesquite and the screwbean mesquite, share various characteristics. They range from a few feet to 10 to 15 feet in height, although the honey and velvet mesquites may reach 30 to 60 feet in especially favorable settings. They may have single or multiple-branched stems, with each plant assuming its own distinctive shape – and come armed with thorns on their smaller branches. Mesquites shed their leaves in the winter but will bloom from spring into summer, bearing small frothy-looking clusters called “catkins” of tiny, five-petalled, pale green or yellowish flowers, which lure numerous pollinating insects. They produce pods that contain hard and long-lasting seeds that must be scarified (cut or slit) before they will germinate. Mesquites have lateral roots that extend far beyond the canopies of the plants and taproots that penetrate well below the surface of the soil. Some mesquites may live for more than two centuries according to Thomas B. Wilson, Robert H. Webb and Thomas L. Thompson, U. S. Department of Agriculture, Forest Service, General Technical Report RMRS-GTR-8.
The honey mesquite, distinguished by smooth-surfaced leaflets, makes its primary home in the Chihuahuan Desert, east of the Continental Divide, although its outer range extends across the Sonoran Desert as well. The closely related velvet mesquite, marked by velvet-surfaced leaflets, has as its primary residence the Sonoran Desert, west of the Continental Divide. The screwbean mesquite, identified by its tightly spiraled bean pods, has established as its basic range the northern Sonoran Desert up into the Mojave Desert. Where distributions of the species overlap, the plants hybridize, often making identification difficult.
Adaptations to the Desert Environment
From crown to root tips, mesquites have evolved a number of adaptations especially designed to help assure survival in the desert environment. Their thorns, sharply pointed and strong, challenge browsing by desert herbivores. (“They will not decay in the flesh or gristle as will prickly pear thorns,” Dobie said, “but will last longer than any flesh in which they become imbedded.”) Their leaves, small and wax coated, minimize transpiration (evaporation of the plant’s water into the atmosphere). During extreme drought, the mesquites may shed their leaves to further conserve moisture. Their flowers, fragrant and delicate, attract the insects, especially the bees, necessary for prolific pollination. Their seeds, abundant and protectively coated, may last for decades, serving as seed banks that improve the odds for wide distribution and successful germination.
Most notably, mesquites’ root systems give the plants a competitive botanical edge in the desert landscape. As hosts to nitrogen-fixing bacteria, they help enrich otherwise impoverished desert soils in which the plants and their progeny grow. In lateral reach, they outcompete other plants in the battle for soil moisture. In their taproots’ downward reach, they find subsurface water, sometimes 150 to perhaps 200 feet below the surface. According to the Arizona-Sonora Desert Museum Internet site, “The mesquite’s root system is the deepest documented; a live root was discovered in a copper mine over 160 feet (50 meters) below the surface.”
During the Ice Ages, which lasted from about 1.8 million to some 10,000 years ago, the mesquites “coevolved with large herbivores, such as mastodons and ground sloths, which ate the pods and then dispersed them widely in their feces,” said the Arizona-Sonora Desert Museum Internet site. The mesquites found the arrangement to be ideal. The seeds became scarified by mastication, preparing them for germination. Seed parasites died when exposed to the animals’ gut juices. The seeds found moisture and nutrients in the animals’ dung. It proved to be a perfect formula for expansion.
Over time, mesquites expanded their range to correspond largely with the herbivores’ range, which extended from flood plains and washes up into prairies, mesas and mountain slopes. When the Ice Ages ended, however, the large herbivores died out, becoming extinct, and rainfall diminished. Deprived of their animal agents for distribution and faced with intensifying competition for water and nutrients, mesquites retreated to the flood plains and washes, forfeiting the higher elevation landscapes to the grasses. Further, mesquites remained contained by frequent wildfires fueled by the grasses, which recovered within a season.
When European descendants moved into the desert Southwest, mesquites found a new ally, domesticated livestock, especially cattle. The new herbivores not only ate and dispersed the pods, the great livestock herds stripped away the desert grasses, eliminating competition and wildfire fuel. In many areas, the opportunistic mesquites moved in to displace grasses. They reclaimed much of their Ice Age range, expanding from the flood plains and washes again up into prairies, mesas and mountain slopes. Mesquites grew up along the historic cattle trails, defining the routes to this day. In fact, mesquites have become established in borrow ditches along modern desert roadways traveled by cattle trucks.
Mesquites as Botanical Enemies
The mesquites’ encroachment into pasturelands and displacement of grasses has frustrated cattlemen, who unwittingly fostered the advance in the first place by overgrazing. “Because dense mesquite outcompetes grass for water and light and because mesquite groves don’t support fire, this conversion is permanent (on a human time scale) without physical intervention,” according to the Arizona-Sonora Desert Museum Internet site.
The mesquites have largely thwarted any attempt at control, including planned burns, herbicides or physical removal – all methods with a high cost and potential environmental damage.
“Fire has been used as a management tool to control mesquite distribution for decades” said Wilson and his associates. However, one authority “determined that within 5 years of a fire in southern Arizona [mesquite] biomass [the total dry weight of the mesquite population] had attained preburn levels.” Mesquites may succumb to frequently repeated burns but so do native grasses, making way for imported invasive species such as the extremely aggressive Lehmann lovegrass.
Herbicides, usually applied by aircraft, have also been used for decades in attempts to control the mesquites. However, “To completely remove mesquite or at least limit its spread in open rangeland using herbicides only, multiple treatments are required; otherwise, the long-term viability of mesquite seeds and their abundance with the seed bank would ensure continual recruitment,” said Wilson and associates. Moreover, “These multiple applications could create adverse side effects to rangeland species diversity and biomass… With the attendant costs of herbicides and aerial application over large areas, a viable long-term management strategy using only herbicides may be impractical.”
Physical removal by methods such as dozing, root plowing, chaining, roller chopping or shredding has reduced mesquite density in pasturelands for brief periods, but the plants soon re-sprout from their bases, more dense than ever. Moreover, said Wilson and his fellow authors, “driving large mechanical equipment through rangeland can cause soil compaction, crush animals, destroy animal burrows, and uproot desirable plant species such as perennial grasses.”
“The white man,” said Dobie, “sowed with over-grazing; he is now reaping thickets of mesquites that are stabbing millions of acres of land into non-productiveness.”
Mesquites as Botanical Friends
If mesquites have arrived as intruders in the view of cattlemen of the Southwest, they have, by contrast, long been a welcome presence in the larders, livestock feed bins, workshops, gardens and medicine cabinets in the perspective of many desert residents.
Cabeza de Vaca, in his Adventures in the Unknown Interior of America (translated and edited by Cyclone Covey), said that “The Indian method of preparing [mesquite beans] is to dig a fairly deep hole in the ground, throw in the beans, and pound them with a club the thickness of a leg and a fathom and a half long, until they are well mashed. Besides the earth that gets mixed in from the bottom and sides of the hole, the Indians add some handfuls, then pound awhile longer. They throw the meal into a basket-like jar and pour water on it until it is covered
“Then all squat round, and each takes out as much as he can with one hand. To the partakers, the dish is a great banquet.”
Something that Belongs
Uninvited guest or welcome neighbor, the mesquites belong to the desert. They evolved in the desert. They play a core role in the desert ecosystem. They both provoke and benefit the people of the desert.
“It comes as near being characteristic of the whole Southwest, including much of Mexico, as any species of plant life known to the region,” said Dobie.
“I ask for no better monument over my grave than a good mesquite tree.”
by Jay W. Sharp
Desert Lil's Cookin' with Mesquite
Cheri's Desert Harvest Mesquite Honey
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