"West of Fort Concho, it (mesquite) becomes dwarfed into a shrub of very large roots... in central Texas and southward beyond San Antonio, the mesquite sometimes has a diameter of two or more feet. Its wood is very durable, makes good fuel and has large tanning properties. A decoction of (mesquite) roots is said to be a good remedy for bowel complaints."-- S B Buckley, Second Annual Report of the Geological and Agricultural Survey of Texas, 1876
Southwest Texas is a land of thorns and spines...
This week we look at some shrubs and cacti native to the country around San Angelo. Many of them have been mentioned in our Journey To The Desert's Edge series and it is long past time to introduce these hardy shrubs to readers who have not yet met them...
With the exception of ocotillo and Desert Hackberry, each plant listed here is either abundant or fairly common in a thirty minute drive from the Oasis of West Texas. Desert Hackberry, according to information provided me by Mr Burr Williams, director of the Sibley Nature Center in Midland, Texas, has an aversion to the cold temperatures which occasionally assault the San Angelo vicinity in winter. A hardier relative-- Celtis reticulata-- can be found in Tom Green County. Ocotillo, sadly, like lechuguilla and creosote bush, doesn't become widespread until our travels take us to Reagan and Crockett counties to the city's west and southwest, respectively...
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| Mesquite "forests" near Turkey Creek, a draw in west central Tom Green County. Once healthy desert grassland, this area was overgrazed into non-productivity. |
Tom Green County, regular readers of this blog know, is home to San Angelo. Plant life here consists of short clumps of grass, odd looking forbs, and a host of xeric succulents and shrubs. Rains usually fall late in the spring. After the land dries and the wildflowers disappear, these plants cover approximately 50% of the ground surface. The other 50% is bare soil and rock...
Mesquite and redberry juniper are probably the two most common Tom Green County shrubs. The latter dots mesas and parts of the desert plains surrounding the flattened hilltops. But the former appears in almost every corner of the county, coating overgrazed rangeland for miles. Mesquite grows so thickly in places that a traveler can think he or she is driving through forests of stunted trees...
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| Prosopis glandulosa-- Mesquite-- in bloom (see credits) |
Mesquite covers a wide area outside its native Chihuahuan and Sonoran Desert homes, so much so that some Texans fail to recognize it as primarily a desert shrub that spread out of the drylands. It ranges into southern Kansas and eastern Texas and California's western desert country. R J Ansley, writing in The Encyclopedia of the Great Plains, observes that the distribution and density of mesquite has increased greatly since the late 1800s. Possible explanations for this include livestock grazing, decreased numbers of wildfire, climate change, and increased atmospheric carbon dioxide levels. We know, from an 1849 military survey conducted by Lt. F T Bryan, mesquite was once but lightly scattered across the eastern Concho Valley of Texas. Prosopis glandulosa dominates this area nowadays. Mesquite (like Catclaw Acacia and Fragrant Mimosa, discussed below) is a bean producing plant, a member of the botanical family Fabaceae...
Many dry country dwellers have another name for Catclaw Acacia and it is not Acacia greggii. They call it "Wait A Minute Bush" due to an uncanny ability to snare the clothes of a passerby with hooked thorns identical in size and shape to a cat's claw. If these hooks actually latch onto a man's flesh, he is prone to use more colorful nouns and gerunds to describe the plant. Acacia greggii rarely ventures outside northern Mexico and the "hot deserts" of the United States-- the Chihuahuan, Sonoran, and Mojave. But it can also be found in drought-prone Central Texas and the Rio Grande Plains...
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| An Acacia greggii-- Catclaw-- branch shows off several of its hooked thorns. (See credits) |
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| Distribution of Acacia greggii in southwestern United States |
Readers who remember their Greek myths may recall Boreas was the god assigned to rule the north wind. The same readers may suspect the "borealis" in Mimosa borealis hints at a northerly range for Fragrant Mimosa. They would be correct. Entering the United States from Mexico, the shrub ranges up to the dry plains of Colorado. Fragrant Mimosa loses its leaves in cold weather (like its cousins acacia and mesquite) and is a thorny little booger (also like them). In normal desert conditions, the shrub rarely exceeds three feet. It thrives in poorly leached limestone soils. Pink blossoms and delicate leaves make M borealis an excellent candidate for xeriscaped gardens...
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| Mimosa borealis-- Fragrant Mimosa (see credits) |
Not surprisingly, thorny plants play an important role in providing shelter and food for wildlife in the Concho Valley and the rest of the Chihuahuan Desert. Large mammals rarely appear in large numbers in dry environments-- little or no shade and widely scattered non-toxic waterholes and rivers make this a necessity...
Two species that do appear in the countryside near San Angelo once co-existed in a delicate balancing act of prey and predator. Cougars prey on deer. In turn, deer browse mesquite pods and cactus tunas (the fruits produced by Prickly Pears). But cougars do not have long lives when they encounter ranchers or farmers with guns. With an abundance of mesquite pods available thanks to overgrazed ranges, deer proliferate. Nature becomes unbalanced...
But we digress. There are other plants important to the survival of desert quails and desert jackrabbits. Lotebush, discussed next, and agarita, discussed shortly, being among the most important of them...
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| Ziziphus obtusifolia-- Lotebush-- between rains (see credits) |
Lotebush loses its leaves as the year progresses. But this loss is not entirely related to changing seasons or drops in temperature. Ziziphus obtusifolia sheds its foliage when sporadic desert rains become almost non-existent. The shrub is not dead. It is dormant. This survival mechanism reverses itself when water becomes available again. The plant's spiked pale branches become almost invisible under a thick coat of small green leaves. Lotebush, also popularly named Gumdrop Tree and Graythorn, rarely dominates a plant community. Look around if you come across one in the dry country of West Texas-- you're likely to see mesquite and pencil cactus in the neighborhood...
[Losing leaves is a fairly common survival mechanism in desert plants. Creosote bush, the hardiest North American drylands species, sheds older leaves and entire branches during extended and extreme drought conditions. Younger and still partly developed Larrea tridentata leaves remain and can survive, according to research conducted by Robert Chew and other University of Southern California scientists, a reduction in water content to less than 50% of their dry weight.
At least two other plants found in the Concho Valley utilize leaf loss strategies to cope with dry conditions. These are Allthorn (Koeberlinia spinosa) and Goatbush (Castela erecta). Unlike Lotebush, both tend to leaflessness almost year round. (When leafed, incidentally, Goatbush and Lotebush appear almost indistinguishable to unpracticed lay eyes despite the fact they belong to different families.) Photosynthesis takes place in the spine-tipped branches of some species, e.g. K spinosa, to compensate for the early leaf loss.]
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| Lycium berlandieri-- Wolfberry-- (see credits) |
Wolfberry aka Lycium berlandieri belongs to the Solanaceae family. Sometimes, I am reluctant to list it as a desert shrub. Healthy green leaves, clusters of bright red berries, and slender gracefully flowing branches don't seem to belong to a drylands species. Then I recall one its other popular names is Desert Thorn and look at a distribution map. Wolfberry closely follows boundaries of the Sonoran and Chihuahuan Deserts, sneaking slightly outside of them to dot occasional counties of the dusty, dry Texas Panhandle and Rio Grande Valley locales. Wolfberry grows below 3000' elevations and frequently associates itself with prickly pear and mesquite...
Yet more thorny plants grace our West Texas drylands...
According to a Tucson Botanical Organization description, Desert Hackberry thorns are "cleverly disguised as branches or cloaked with rough, small, oval leaves". In Texas, it grows on plains above the Rio Grande where locals call it Granjeno and in the dry Big Bend and southwesternmost Concho Valley in Crockett County. Elsewhere, Celtis pallida sprouts up across southwestern New Mexico and throughout central and southern Arizona. Native peoples discovered Granjeno fruits to be slightly bitter but edible. Scientists say these little orange globes contain up to 20% protein. They are also a good source of calcium and phosphorous...
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| Celtis pallida-- Desert Hackberry-- (see credits) |
[Desert Hackberry offers us some insight into the challenges faced by scientists as they attempt to understand the natural world and make it comprehensible to the rest of us. Among botanists, one daunting task is to identify and name plants with universal consistency. As part of this ongoing process, the venerable name Celtis pallida is slowly giving way to Celtis ehrenbergia. The romantic in me resists this since the older name celebrates the pale branches of this relative of elm trees in a linguistically satisfying way.]
Agarita also produces edible berries. These can be used to make a slightly tart jam. Small and red, they appear and ripen after yellow flowers in the late winter and early spring months make an already attractive holly-like plant more beautiful. At home on limestone soils, Mahonia trifoliata belongs to the Berberidaceae Family. The shrub survives in other soils if they are well drained and the plant receives much sunlight. Agarita (aka Algerita and Chaparral Berry) is not strictly a thorn plant but is included here because its leaves are made up of three leaflets, each of which ends in razor sharp tips. Small mammals and birds hide in and under Agarita, an ideal ornamental plant that may be placed under windows to discourage burglars...
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| Mahonia trifoliata-- Agarita-- (see credits) |
Folks new to desert living or people thumbing through a glossy coffee table sometimes mistake Ocotillo (Fouquieria splendens) for a species of cactus. It is actually a "bizarre desert shrub", as Delena Tull and George Miller comment in their Wildflowers, Trees, and Shrubs of Texas. Ocotillo does not venture outside desert climates in its natural range which is the western Concho Valley and Trans-Pecos of Texas, the southern half of New Mexico, almost all of Arizona, southern Nevada, and southwestern California. It is a wandlike plant which can reach a height of 30'. Ocotillo is generally leafless but may be covered with simple, alternate leaves and red tubular flowers when the desert receives rain. A century ago, ranchers cultivated Ocotillo to create living fences, knowing that only drunks or fools would brave the countless thorns protecting the sole member of the Fouquieriaceae family in the United States...
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| Fouquieria splendens-- Ocotillo-- (see credits) |
BONAP lists at least a dozen cactus species growing on Tom Green County rangeland. Prickly Pear is the best known, both locally and in the world beyond Texas. The most common member of the Cactaceae family in the county is likely the Prickly Pear known as Opuntia engelmannii...
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| Opuntia engelmannii-- Prickly Pear Cactus-- (see credit) |
Like mesquite, it is a plant that escaped its desert environment to spread to slightly moister climates. Prickly Pears can be found in the Mojave, Sonoran, and Chihuahuan Deserts and as far north as the southeastern corner of Utah. But it also grows in the Texas Hill Country and is no stranger to the Texas Gulf Coast. Prickly Pears-- like all true cacti-- are natives of the Western Hemisphere. Travelers to distant corners of the globe may encounter them as introduced species. Historians tell us, for instance, that Prickly Pears were brought to Australia from Brazil in 1788...
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| Immature Prickly Pear Fruit |
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CREDITS
Note: All photographs for this essay were located through Google Images or Wikipedia, without authoritative source or ownership information except as noted: Prosopis glandulosa photograph by Russ Kleinman from wnmu.edu; Acacia greggii twig photograph by Steven J Baskauf from cas.vanderbilt.edu; Mimosa borealis from photos.wumple.com; Ziziphus obtusifolia from wnmu.edu; Lycium berlandieri photograph by L R Landrum from swbiodiversity.org; Celtis pallida photograph by Thomas Van Devender from swbiodiversity.org; Fouquieria splendens from abdnha,org; Mahonia trifoliata from georgiavines.com; Opuntia engelmannii photograph by Richard Felger from wnmu.edu; Distribution maps from BONAP.org; Mesquite Forests and Prickly Pear Fruits photographs from Louis R Nugent
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