Natural History

Sowthistle – a new weed in my yard

sowthistle1A new weed has sprouted in my yard. With the help of a botanist at the Arizona-Sonora Desert Museum, this new plant is identified as the genus Sonchus, commonly called sowthistle. Sowthistle species occur in temperate zones worldwide. Arizona has two species, Common Sowthistle (Sonchus oleraceus), the one in my yard, and Spiny Sowthistle (Sonchus asper). These plants are related to dandelions and are members of the sunflower family. For an idea of the plant size, the large leaf in the center of the photo is 10 inches long.

The name “Sowthistle” refers to the fact that pigs are especially fond of the leaves and stems. So are rabbits. This plant is also called “hare thistle” or “hare lettuce” in some parts of the world.

The leaves are also used by humans, especially in Chinese cooking. The leaves can be eaten as a salad green or cooked and used like spinach. Blanching removes a slightly bitter taste. (Source) I have not tried it.

“This plant has powerful medicinal properties, with some toxicity, but at the same time it is also highly nutritious. It contains, per 100g, around 30mg of vitamin C, 1500 mg of calcium and 45 mg of iIron. The dried leaves contain up to 28g of protein per 100g – a great nutritional supplement. Use only young leaves as edibles, raw, in salads or cooked, as spinach.” (Source)

Medicinal uses are the same as for dandelions:

“In the past, dandelion roots and leaves were used to treat liver problems. Native Americans also boiled dandelion in water and took it to treat kidney disease, swelling, skin problems, heartburn, and upset stomach. In traditional Chinese medicine (TCM), dandelion has been used to treat stomach problems, appendicitis, and breast problems, such as inflammation or lack of milk flow. In Europe, dandelion was used in remedies for fever, boils, eye problems, diabetes, and diarrhea.” (See more from the University of Maryland Medical Center.)

Sow thistles exude a milky latex when any part of the plant is cut or damaged, and it is from this fact that the plants obtained the common name, “sow thistle”, as they were fed to lactating sows in the belief that milk production would increase. Sow thistles are known as “milk thistles” in some regions, although true milk thistles belong to the genus Silybum. (Source)

The yellow flowers are about 1.25 inches in diameter and attract bees, flies, and aphids. The flowers turn into dandelion-like tufts and the seeds go floating off in the wind.

Common Sowthistle is classified as an annual herb and can grow up to four feet high. Other species of Sonchus are perennials.

Opossums in Arizona?



Opossums are common in the eastern US but are rare in the west. Strangely enough, the so-called Virginia opossum (Didelphis virginiana) occurs in Tucson and other parts of Arizona. This is the only species of marsupials that occurs in the US. (Marsupials nurse their young in pouches. The kangaroo is probably the best known marsupial.)

An amusing decription written in early Spanish colonial times quoted in an article in Scientific American, describes an opossum as “a monstrous beast with a snout like a fox, a tail like a marmoset, ears like a bat, hands like a man, and feet like an ape, bearing her whelps about with her in an outward belly much like a large bag or purse.” (Source)

According to Wikipedia:

Virginia opossums can vary considerably in size, with larger specimens found to the north of the opossum’s range and smaller specimens in the tropics. They measure 13–37 in long from their snout to the base of the tail, with the tail adding another 8.5–19 in. Weight for males ranges from 1.7 to 14 lb and for females from 11 ounces to 8.2 lb. They are one of the world’s most variably sized mammals, since a large male from northern North America weighs about 20 times as much as a small female from the tropics. Their coats are a dull grayish brown, other than on their faces, which are white. Opossums have long, hairless, prehensile tails, which can be used to grab branches and carry small objects. They also have hairless ears and a long, flat nose. Opossums have 50 teeth, more than any other North American land mammal, and opposable, clawless thumbs on their rear limbs.

Opossums have 13 nipples, arranged in a circle of 12 with one in the middle. Perhaps surprisingly for such a widespread and successful species, the Virginia opossum has one of the lowest encephalization quotients of any marsupial. Its brain is one-fifth the size of a raccoon’s.

Opossums are mainly nocturnal and omnivorous. A large part of their diet is insects and other invertebrates, but they also eat the eggs of chickens and wild birds, fruits and berries, pet food left out in the yard, and garbage.

According to an article in the Journal of Mammology (November, 1952), an adult female opossum was captured (December, 1949) at the Rincon Stock Farm on Fort Lowell Road in Tucson. The following May, an adult male was found about four miles from the Farm. The author of this paper speculates that these animals were introduced from elsewhere, although he does mention that wild opossums lived in eastern New Mexico at the time.

A more recent article (2011) in the Western North American Naturalist journal reports opossums in Yavapai County, Arizona. The paper’s abstract reads:

The Virginia opossum (Didelphis virginiana) is the only marsupial native to the United States. In recent times, D. virginiana has expanded its range through natural movements and anthropogenic introductions. Didelphis virginiana has been present in southern Arizona owing to range expansion by the Mexican subspecies (D. v. californica) and anthropogenic introductions of the eastern subspecies (D. v. virginiana). Here, we document the recent collection of an opossum in central

Arizona. We also discuss how it possibly moved there and report on its stomach contents at the time of collection.

There are also reports of opossums in the Phoenix area.

Opossums react to a threat by feigning death, hence the saying “playing possum.” Opossums, like most marsupials, have unusually short lifespans for their size and metabolic rate. The Virginia opossum has a lifespan in the wild of only about two years.

There is some North American mythology about opossums. “In North America, Opossum sometimes appears in legends as a buffoon or braggart, whose habit of playing dead stems from embarrassment over having made a fool of himself. In Central America and parts of southern Mexico, Opossum occasionally plays the role of a trickster or an animal hero who escapes from danger by using his wits. Opossums are also symbols of fertility in some Mexican tribes, and a drink made with an opossum’s tail is still used by some Nahuatl women as folk medicine to help deliver babies. In some South American tribes, Opossum plays a more important mythological role as the Fire-Bringer.” Read more here.


The Cactus Mouse – another creature of the night


The Cactus mouse (Peromyscus eremicus) is one of eight species in the genus Peromyscus that inhabit Arizona. All are similar-looking grayish-brown, with white bellies and feet, and large ears. They are about 3.5 inches long. The cactus mouse has a sparsely furred tail with a slight tuft at the tip. “Females weigh slightly more than males and are significantly larger in body length, ear length, length of mandible and bullar width of skull. Cactus mice can be identified by having naked soles on their hind feet, and almost naked tails which are usually the same length or longer than the animals body length.” (Source)

The Cactus mouse ranges from southern California and Nevada, through southern Arizona and New Mexico, west Texas into northern Mexico. They are common in washes and rocky hillsides, in sandy deserts and desert foothills. Depending on location, they may breed throughout the year. A female may produce 3 to 4 litters per year, each with 4 to 5 young.


Cactus mice are nocturnal feeders. They eat seeds, fruit, and succulent plant material. Their diet includes mesquite beans and leaves, and insects. During the day they remain in burrows in clumps of cacti, in the ground, or among rocks. Their nests are usually a ball of grasses or twigs.

According to the Arizona-Sonora Desert Museum:

“The cactus mouse often climbs around in vegetation and brush, searching for seeds and fruits to eat. It may nest in wood piles or rock piles, or use the abandoned burrows of other animals. Although this mouse needs less water than many others and is desert-adapted, it may estivate or go into a torpor in the summer when resources for food and moisture are not available.”

“These little rodents are at the bottom of the vertebrate food chain, preyed upon by everything from coyotes and snakes to hawks and bobcats. In response, they breed prolifically, with some species, like the cotton rats, able to produce eight to ten litters a year. Populations still fluctuate with drought and predation, but the mice and rats are able to respond to good conditions by rapidly rebuilding their numbers.”

“All rodents, including the mice and rats, are gnawers. Their teeth are ever-growing and must be kept trimmed down by constant gnawing. A layer of hard orange enamel covers the front surface of the teeth. The rest of the tooth is softer and wears down quicker than the enamel as the rodent gnaws, thus creating a chisel-like shape to the front teeth that is unique to the rodent family.”

Other desert rodents:

Creatures of the night – Pocket Mice

Ferocious Grasshopper mouse

Kangaroo rat

Pack Rats are Desert Archaeologists








Attack of the Phainopepla


The Phainopepla (Phainopepla nitens) is a pretty bird, but around my house one has been pretty messy. For several weeks, a male Phainopepla has been feasting on the berries of a desert mistletoe plant. It has been peeping in the window. At times it attacks its reflection by pecking at the window and flying up and down the glass. It is apparently trying to drive off what it thinks is a competitor. Does he look angry?

The Phainopepla is a crested bird slightly smaller than a cardinal. It has a body length of 7- to 8 inches and a wingspan of 11 inches. The males are shiny black with red eyes, long tail and a white patch on the wings which is conspicuous in flight. Females and immature birds are all gray. The name “Phainopepla” comes from the Greek for “shining robe,” a fitting description of the shiny, jet-black plumage of the adult male. The Phainopepla is one of the four species of silky-flycatchers and the only one that occurs in the U.S. The others inhabit Mexico and Central America.

According to the Cornell Lab of Ornithology:

“… the Phainopepla is unique in taxonomy, distribution, and behavior. It is particularly notable for its enigmatic pattern of breeding twice each year, in two different habitats.” It breeds in both the desert and in arid woodlands.

Cornell says that “An individual Phainopepla eats at least 1,100 mistletoe berries per day, when they are available.” (My visitor deposits the remains of these sticky berries on my window ledge and ironwork.)

“The Phainopepla exhibits strikingly different behaviors in its two habitats. In the desert, it is territorial, actively defending nesting and foraging sites, while in the woodlands it is colonial, with as many as four nesting pairs sharing one large tree.

“The Phainopepla rarely drinks water, even though research indicates that it loses about 95 percent of its body mass in water per day. Instead, it gets the water it needs from its diet of mistletoe.” Phainopepla also eat other berries and flying insects.

According to the Arizona-Sonora Desert Museum:

“This bird nests in early spring in mesquite brushlands, usually well up in a stout fork or horizontal branch of a tree. The smooth, slightly glossy eggs usually number two to three per clutch, and are grayish-white or pinkish, finely and profusely spotted with black, pale lavender, or gray. The eggs are incubated by both sexes (possibly the major portion by the male) for 14 to 15 days. The young are tended by both parents and leave the nest at 18 to 19 days.”

The Phainopepla, when pursued by predators or handled by humans, mimics the calls of other birds; imitations of at least 13 species have been recorded. (Listen to sounds)

As the supply of mistletoe berries dwindle, my Phainopepla is now spending about half his time attacking a neighbor’s window which is a little closer to the berry source.



Eurasian Collared-Doves


Have you seen this bird? Collared doves have been showing up in my backyard for the past few years. They flock with other doves and I rarely seen more than one collared dove at a time.

The Eurasian Collared-Dove (Streptopelia decaocto) is about 12 inches long and has a wingspan of about 14 inches which makes it larger than a Mourning dove and about the same size as a White-winged dove.

According to the Cornell Lab of Ornithology:

“Eurasian Collared-Doves made their way to North America via the Bahamas, where several birds escaped from a pet shop during a mid-1970s burglary; the shop owner then released the rest of the flock of approximately 50 doves. Others were set free on the island of Guadeloupe when a volcano threatened eruption. From these two sites the birds likely spread to Florida, and now occur over most of North America.”

Eurasian Collared-Doves eat mainly seeds and cereal grains. They will occasionally eat berries, plant greens, and bugs. Their principal habitat appears to be urban and suburban areas, especially where people put out bird feeders. They may also occur on farms.

“Mainly ground foragers, they peck at grain and seeds scattered beneath backyard feeders and on feeding platforms, or spilled at farmyards. Flocks of 10 to several hundred doves may gather at prime spots. Although they can feed peacefully in mixed flocks, Eurasian Collared-Doves will also chase off other birds, including Mourning Doves, cardinals, and Blue Jays.” (Cornell)

Nesting (source, Cornell):

“The male dove brings the female twigs, grasses, roots and other nesting materials, which he sometimes pushes directly under her. Over 1 to 3 days she builds a simple platform nest, which may include feathers, wool, string and wire. A pair often uses the same nest for multiple broods during the year, and may renovate old nests.

“Males show females potential nest sites in trees and on buildings, giving a low- pitched, slow koo-KOO-kook call at each site (listen here). Nests are usually built 10 or more feet above the ground. In warmer regions, Eurasian Collared-Doves can nest year-round, which may help explain their success as colonizers.”

“Eurasian Collared-Doves are one of very few species that can drink “head down,” submerging their bills and sucking water as though drinking through a straw. Most birds must scoop water and tip the head back to let it run down into the throat.” (Cornell)

Eurasian Collared-Doves may be mistaken for Ringed Turtle Doves which are slightly smaller and lighter in color. According to the Sibley Guide to Birds, the Ringed Turtle Dove is a domestic variety, not a naturally occurring species, and it fares poorly in the wild.

See also:

Mourning Doves

White-winged Doves

Black-necked Stilt

black-necked-stiltThe Black-necked Stilt (Himantopus mexicanus) is a fun bird to watch as it noisily feeds along shorelines. (Listen to sounds). This Stilt occurs in the southern and western U.S. Its range includes the Great Basin, Sonoran and Chihuahuan deserts near bodies of water. The Sonoran Desert, south to the tip of Baja, California Mexico, is within its year-round range. You can see some at the Arizona-Sonora Desert Museum where I took the photograph.

black-necked-stilt-rangeThe Black-necked Stilt stands about 18 inches high and has a wingspan of 28 inches. It has a black head, neck and back over a white body. Its bill is long and black. One of its most striking features is its very long, red/orange legs. “ They have the second-longest legs in proportion to their bodies of any bird, exceeded only by flamingos.” “Five species of rather similar-looking stilts are recognized in the genus Himantopus.” (Source)

Stilts forage, often in groups, in shallow water or along shorelines for insects and other prey. Cornell Lab of Ornithology adds: “Black-necked Stilts wade in shallow waters to capture their meals of aquatic invertebrates and fish. They often consume such fare as crawfish, brine flies, brine shrimp, beetles, water boatmen, and tadpoles. They peck, snatch, and plunge their heads into the water in pursuit of their food, and will herd fish into shallow waters to trap them there.”

According to ASDM: “These are ground-nesting birds, whose eggs are well camouflaged and whose downy chicks can run about and find their own food shortly after hatching. Adults defend eggs or chicks with a repertoire of distraction displays. These birds are good runners and strong flyers.”

According to Cornell: “Male and female Black-necked Stilts trade off the job of constructing the nest. While one mate observes, the other scrapes into the dirt with breast and feet to form a depression about 2 inches deep. As they dig, they throw small bits of lining over their back into the nest. Most lining is added to the nest during incubation, and consists of whatever material is closest to the nest, including grasses, shells, mud chips, pebbles, and bones.” “ During breeding and during winter, they are strongly territorial birds, and are particularly aggressive to chicks that are not their own. When not breeding, Black-necked Stilts roost and forage in closely packed groups, often staying within a foot of each other. Black-necked Stilts are semicolonial when nesting, and they participate en masse in anti-predator displays. The displays include one in which nonincubating birds fly up to mob predators, and one in which all birds encircle a predator, hop up and down, and flap their wings.”

A more general note on shorebirds from ASDM:

Shorebirds in general do most of their foraging along the water’s edge, probing in soft mud or picking at the surface in search of tiny invertebrates. They belong to several related families. The largest shorebird group is the sandpiper family (Scolopacidae); nearly two dozen species of sandpipers migrate through the Sonoran Desert, but for the most part their presence with us is fleeting, a few days’ stopover as they travel between breeding grounds on Arctic tundra and wintering grounds on southern coasts. More relevant here are two long-legged waders and one plover that are with us for much of the year.

The avocets and stilts make up a small family, with only a few species worldwide. All are slim birds with long necks, thin bills, very long legs, and striking patterns. All forage in shallow water, feeding on small invertebrates. North America has one avocet and one stilt. Both have ranges which extend into the Sonoran Desert, where they seem to have benefited from human activity; most of their modern nesting sites are around the edges of artificial ponds.

Study: Forest Fires in Sierra Nevada Driven by Past Land Use not Climate Change

Researchers from the University of Arizona and Penn State studied fire regimes in the Sierra Nevada Mountain of California for the period 1600 to 2015 and found that land use changes, not climate, were the principal controlling factors.

This result was apparently a surprise to the researchers since they set out to correlate climate with the fires.

“Initially, we did work to see if we could develop long-lead forecasts for fire in the area — six to 18 months in the future — using climate patterns such as El Niño,” said Alan H. Taylor, professor of geography, Penn State. “This would be a significant help because we could place resources in the west if forecasts indicated it would be dry and the southeast would be wet. However, the climate relationships with fire did not consistently track.”

“We were expecting to find climatic drivers,” said lead co-author Valerie Trouet, a UA associate professor of dendrochronology. “We didn’t find them.”

The researchers used tree ring data from 29 sites, historical documents, and 20th Century records of areas burned.

From the UofA press release:

For the years 1600 to 2015, the team found four periods, each lasting at least 55 years, where the frequency and extent of forest fires clearly differed from the time period before or after. The team found the fire regimes corresponded to different types of human occupation and use of the land: the pre-settlement period to the Spanish colonial period; the colonial period to the California Gold Rush; the Gold Rush to the Smokey Bear/fire suppression period; and the Smokey Bear/fire suppression era to present. Finding that fire activity and human land use are closely linked means people can affect the severity and frequency of future forest fires through managing the fuel buildup and other land management practices — even in the face of rising temperatures from climate change.

From the Penn State press release:

Early fires, because they were more frequent, with less fuel build-up, were “good” fires. They burned through the forest, consumed understory fuels and left the majority of trees unharmed. The Native American mosaic of burned and unburned areas prevented fires from continuously spreading.

From 1776 to 1865 the second fire regime, characterized by Spanish colonialism and the depopulation of Native Americans in the area, shows more land burned. European settlers brought diseases against which Native Americans had no immunity and the population suffered. The Spanish built a string of missions in California beginning in 1769 and relocated remaining Native Americans to the mission areas. In 1793, there was a ban on burning to preserve forage, disrupting the pre-colonial Native American burning practices. The incidence of fires became more sensitive to drought and the fire regime changed, creating the time when fires were largest and most closely coupled with climate.

The third fire period is from 1866 to 1903 and was initiated by the California gold rush, when thousands of people poured into the area. Settlement by large numbers of new immigrants began to break up the forest fuel and the creation of large herds of animals, especially sheep, removed large amounts of understory and changed the fire regime.

The fourth fire period began in 1904 and is linked to the federal government’s policy of fire suppression on government lands. The reason pre-colonial and Spanish colonial fire levels were so much higher than today is that the current fire regime is one of suppressions with an extremely low incidence of fires compared to the past. However, suppression over the last century has allowed fuel to build up on the forest floor and opened the door for “bad” fires that destroy the forest canopy and burn large areas of land.

(UofA press release, Penn State press release, paper abstract )

This finding contradicts an alarmist story printed in the Arizona Daily Star this past October (see third reference below).


See also:

Wildfires and Warming – Relationship not so clear
Claim: “Worsening Wildfires Linked to Temp Rise

Media hype about forest fires and global warming
Mega-fires in Southwest due to forest mismanagement

Golden Fleece – a hardy desert flowering plant


Golden fleece (Thymophylla pentachaeta, formerly Dyssodia pentachaeta) is known by many names including: Dahlberg daisy, dogweed, golden dyssodia, fiveneedle pricklyleaf, and golden dogbane. The plant is a member of the Asteraceae or Compositae (sunflower) family. Four varieties are recognized in Arizona.

Generally, individual plants can produce a dome of yellow, daisy-like flowers (about one-half inch in diameter) and grayish-green, lacy leaves which produce a fetid odor when crushed. The flowers are on individual stems above the doming foliage. The dome can be up to about 7 inches tall and 10 inches wide. Some sources say these plants are perennial and can spread profusely from seeds. Other sources say individual plants are short-lived, but are quickly replaced by new seedlings. When the flowers are done, you may see tiny seeds floating away on their parachutes, but most seeds are dropped to the ground.

For a more technical description and photos, see Southwest Desert Flora. Google Images here.


I have many of these plants in my front yard. I did not plant any of them – they just happened. Those that bloom among a flower bed get watered, but others in the yard survive without watering. Some do appear to be perennial.


Golden fleece is native to the southwestern U.S. and Mexico between elevations of 2,500 to 4,500 feet.

Golden fleece blooms from March through October, and in mild temperature areas, the flowers may last through the winter. This plant will tolerate full desert sun.

The flowers attract bees and butterflies, and some butterfly caterpillars eat the leaves. Golden fleece can be good garden ground cover that needs to be watered infrequently. Rabbits tend to leave it alone.

War on the Range – Ranchers versus Mesquite



Southern Arizona ranchers have been battling mesquite trees for almost 100 years. The principal reason is that mesquite trees and shrubs suck up the water and thereby degrade the range making it less suitable for raising livestock. It also makes the grasslands less accommodating to wildlife.

Mesquite is a very hardy plant that produces an abundance of seed pods. The seeds and pods are collected and stored by rodents. Many animals, including livestock and deer, eat the seed pods, but the seeds themselves pass through undigested and are deposited with some fertilizer.

The problem as described to me by a southern Arizona rancher:

Southern Arizona is characterized by intermittent drought. This results in marked death loss of the perennial forage grasses, however, drought seldom causes death of whole mesquite plants. Mesquite have a long tap root enabling it to reach underground moisture and can tolerate drought. Grasses do not have that advantage. As the tree grows it demands more moisture. The result is each year, depending on the rainfall, less and less forage is produced as the tree shades the ground and quickly takes up the moisture. As the mesquite grow, noxious plants also become established with their deeper roots which make them drought resistant. These include burroweed and snakeweed. These also crowd out grass. As the ground is bare, when a heavy rain falls there is not grass and grass roots to hold the soil so erosion becomes an issue.

According to University of Arizona Technical Bulletin 74, published in 1938:

Certain range lands of the grassland type in southern Arizona are undergoing an invasion by the mesquite tree and noxious shrubs to the extent that the native stand of palatable forage is being materially reduced. The development of this problem has taken place at a pace gradual enough that its seriousness was not fully realized by stockmen until the cumulative effects of some forty years’ transition in the vegetation type of the affected areas became increasingly apparent.

The report goes on to discuss various methods of mesquite eradication including use of petroleum products, arsenic, acid sprays, and other chemical means. These methods proved ultimately ineffective. Petroleum did not kill the roots so the mesquite soon sprouted new growth. The chemicals remained on the stumps and were thus dangerous to livestock and wildlife. Burning individual trees was also ineffective. Only sodium arsenite solution would kill the roots, but it was difficult to prepare and handle.

The US Department of Agriculture weighed in with Circular 908 published in 1952:

One of the most serious and perplexing problems in southeastern Arizona is mesquite invasion of grasslands. Mesquite occurs there in varying degrees of abundance on 9 million acres of range land. The problem is likewise serious elsewhere in the Southwest. Mesquite is now firmly established on considerably more than 70 million acres of range in Texas, New Mexico, and Arizona. An estimated half of the area now occupied by mesquite has been invaded since the advent of domestic livestock. The increase of mesquite is viewed with ever-increasing alarm by range operators.

The principal reasons for concern are : (1) Mesquite, even under moderate grazing use, is still persistently increasing both by invading open grassland and by thickening of old stands. (2) Cutting mesquite, especially in bottom-land areas, usually results in an impenetrable thicket of sprout regrowth and new seedlings. In many of these “jungles,” grazing has had to be abandoned. (3) Livestock handling costs are increased, especially in dense upland mesquite thickets where it is difficult to gather livestock for market or to find screwworm-infested animals for treatment. (4) Increases in mesquite are usually accompanied by decreases in quantity and quality of perennial grass forage and corresponding reductions in livestock production. (5) Still more serious from a long-time viewpoint is the accelerated erosion generally found on uplands as well as bottom lands wherever mesquite has encroached.

The USDA further opines on the cause of the mesquite invasion:

The probability is that neither protection nor heavy grazing has much to do with the increase of shrubs here, but it is primarily the direct result of the prevention of fires.

I spoke with several ranchers who are battling mesquite in southern Arizona. For many years they have been using mechanical means to cut the trees and shrubs and digging out the roots. They try to remove at least 80% of the mesquite. Studies at the Santa Rita Experimental Range show that removing about 80% and leaving some mature trees makes the range more amenable to wildlife than thick mesquite stands or open range.

Before removal work can be done, the ranchers have to make surveys for endangered species such as the Pima Pineapple Cactus, which was listed in 1993 (and there is still no recovery plan). They also have to survey for cultural resources.

The mechanical method means bulldozers to knock down the trees and dig up the roots. One rancher told me it costs $300-$400 per acre and can get only one acre per hour. This is an expensive and tedious operation.

More recently, ranchers have been experimenting with chemical warfare again. Dow Chemical has developed an herbicide that is specific for mesquite. It is deployed by helicopter spraying. This costs about $106 per acre and can cover 80 acres per hour. This is similar to crop dusting operations used on farms.

The ranchers say another main reason for mesquite removal is to reduce soil erosion and restore native grasses. Since chemical removal has begun, ranchers have noticed return of many native grass species.

After reading a version of this article published in the Arizona Daily Independent, another southern Arizona rancher send me these comments:

Mesquite proliferation can be a problem, but they multiply and then decrease quite apart from grazing. It’s fairly cyclic and occurs even where no grazing has occurred (there’s a very deep and large area surrounded by cliffs in Mexico–never grazed–where scientists measured mesquite increase. It increased at the same rate as in the grazed pastures elsewhere.

Mesquites do consume a lot of water and at greater than 20% cover they are problematic, however, at lower than 20% overall, they are a major feed item for both cattle and wildlife–the beans are highly nutritious and so are the leaves. Also, they make a rich, nitrogen-enhanced (they are nitrogen fixers) soil beneath the tree which grows and maintains good native perennials, just so long as the tree cover is not beyond 20-30% and sunlight reaches the area below the tree for some good part of the day. Shade is also good! The upshot is: these trees are natives and are highly adapted to this climate; they have significant value for both wildlife and cattle as forage and as shade for natives that prefer less direct sun like plains bristlegrass and viney mesquite (that’s a grass in spite of the name) and others.

Here we are not at war with mesquites; however there are areas where their density exceeds desirable. Right now the cost of control (just private land–forget trying to do anything on federally managed land) and the issues with flood plains or critical habitat for assorted species are overwhelming and make constructive control financially impractical.

The screw worm issue mentioned in that 1952 publication is past tense; screw worms were effectively controlled decades ago by the propagation and dissemination of sterile male screw worms by the federal govt. and ranchers. It used to be a huge problem in the summer–now not, We can only surmise that such control would be met by howls of opposition from those who would prefer not to eradicate pest insects.

Controlling mesquite makes the range more productive, saves water, and benefits wildlife.


For information on traditional use of mesquite trees see:

Mesquite trees provide food, fuel, medicine, and more


Velvetpod Mimosa – a desert survivor

Velvetpod mimosa

Velvetpod fruit








The Velvetpod Mimosa (Mimosa dysocarpa) is an extremely drought and heat tolerant legume plant that is native to Arizona, New Mexico, and Texas. It blooms during the hottest part of the summer. It occurs mainly along arroyos and washes, 3500-6500 ft. elevation.

The mimosa is a woody shrub that grows three to six feet tall. The branches have large, sharp thorns. The flowers are showy but misleading because you see the flower filaments not the petals. The petals are very tiny and fused together. (See photos here) Fresh flowers are magenta to deep pink, but fade to light pink and white as they age. The leaves are fuzzy.

The pollen is a mild allergen. Butterflies, bees, birds, and moths are the principal pollinators.

After the flowers are pollinated, the fruit is a one- to two-inch-long bean covered with tiny hairs which look like velvet, hence the name. The bean pod is also protected by four large thorns. These beans are a favorite of quails. The plant is a favorite of Coues white-tailed deer in the Santa Rita Mountains of Arizona (source).

The velvetpod mimosa is often used in xeriscape gardens.

The velvetpod mimosa is in the Mimosoideae subfamily of the Leguminosae family (Fabaceae). For some perspective, here is what the Arizona-Sonora Desert Museum says about this plant group:

“Legumes are a very large family of 16,000 species in nearly all of the world’s habitats. Champion drought tolerators, they are most abundant in the arid tropics. Their prevalence in the Sonoran Desert flora (for example, there are 53 legume species in the Tucson Mountains, 8% of its plants) reflects this desert’s tropical origin. North of the Mexican border most of the common Sonoran Desert trees are legumes.”

“The family was named Leguminosae for its fruit, which in most species is a legume (the technical term for bean pod, a single-chambered capsule enclosing what appears to be a single row of seeds that is actually two rows — alternate seeds are attached to opposite halves of the pod). There are three subfamilies with flowers that look very different from one another at first glance, but arose from a common pattern: Caesalpinioideae, Faboideae, and Mimosoideae.”

Some of my other articles about plants in the legume family are:

Mesquite Trees Provide Food and a Pharmacy

Palo Verde Trees Will Turn the Desert Golden

Desert Ironwood with video