Mark A. Dimmitt

The approximately 1300 species of chenopods worldwide range from annual herbs to trees. Many species have C4 photosynthesis. The flowers are tiny and inconspicuous, but some species bear showy masses of fruits. Chenopods are common in deserts and especially in saline or alkaline soils. Spinach, beets, sugar beets, chard, and epazote are members with economic value. The most common chenopods in our region are several species of Atriplex (saltbush) and Chenopodium (goosefoot, pigweed); the latter genus contains both native and exotic herbs.

Atriplex canescens

English name: fourwing saltbush
Spanish names: cenizo (ash-gray), chamizo (thatch, brush), costilla de vaca (cow’s rib), saladillo (salted)

Description

Fourwing saltbush is a densely-branched, evergreen shrub 3 to 6 feet (1-2 m) tall with gray foliage. Female plants bear large masses of fruits, each with 4 large winglike membranes.

Fourwing saltbush (Atriplex canescens)

Range

This shrub is widespread in the desert Southwest, centered in the Great Basin and extending into Canada, Mexico, and the western Great Plains. It is often the dominant plant in valleys with saline or alkaline soils.

Notes

There is something of a mystery concerning this saltbush’s ecological needs. Despite the significant climate changes from the glacial to the present interglacial period, the plant has stayed put—its geographic distribution in the southwest U.S. has not changed. On the other hand, its elevational range changes dramatically with soil type. It grows 1600 feet (500 m) higher on shale soils than on soils derived from igneous rocks.

The leaves of saltbush species appear grayish because they cope with saline soils by secreting excess salt into tiny hairs on the leaf surfaces. The hairs die from high salt concentration, leaving a deposit of salt crystals on the surface that reflects some of the intense light that would otherwise overload the photosynthetic system.

Cattlemen regard saltbush as drought insurance. Cattle rely on these bushes when grasses fail to produce a good crop due to insufficient rains.

Other species of Atriplex in our region include A. hymenelytra (desert holly) and A. lentiformis (quailbush). The former grows in mounds to 4 feet (1.2 m) tall and wide with white holly-shaped foliage; the latter gets much bigger, to 8 by 12 feet (2.4 by 3.7 m). Both species grow in the lowest desert elevations, as does another species with tiny leaves, A. polycarpa, desert saltbush, a shrub considered by far the most important browse plant in its range before agriculture displaced much of it. If water is available, these plants can photosynthesize on the hottest days, when most other plants are stressed and forced to shut down; they exemplify the adaptive value of C4 photosynthesis. A. lentiformis seeds were gathered by the O’odham as emergency food, and soap was made from the leaves.

Salsola tragus

[Salsola iberica, S. kali] English names: Russian thistle, tumble- weed, wind witch, leap the field
Spanish names: chamizo volador (flying bush), maromero

Description

Russian thistle is a nearly spherical annual herb, usually about 2 feet (60 cm) tall, but more than twice that in favorable conditions. The threadlike leaves are spine-tipped. The dried plant breaks from its root and blows across the ground, dispersing seeds as it tumbles.

Range

The plant is native to Eurasia, but now occurs all over western North America in disturbed soils.

Russian thistle Salsola tragus

Notes

Though it’s an integral part of Western lore, tumbleweed is an exotic, very harmful weed. (The familiar song “Tumbling Tumbleweeds” was written in Tucson and first published as a poem in a University of Arizona literary quarterly. The Sons of the Pioneers, a singing group of the 1940s, made the song popular, and retired to Tucson 40 years later.)

Tumbleweed was first noticed in South Dakota in the 1880s, brought in as a contaminant in crop seeds from Europe. By the turn of the century it had spread to the Pacific coast and the Mexican border. It has become a troublesome pest in disturbed soils such as agricultural fields and graded road shoulders. It is rare or absent in undisturbed habitat. In some naturally unstable habitats, such as sand dunes, Russian thistle has become the dominant plant and is crowding out native species.

Salicornia bigelovii

English names: pickleweed, glasswort
Spanish name: none known

Description

This pickleweed is an annual halophyte (plant that tolerates salty soil). It consists of succulent jointed stems that resemble strings of little pickles; plants grow from less than a foot (30 cm) to 3 feet (0.9 m) tall in different populations. The inconspicuous flowers are wind-pollinated.

Pickleweed (Salicornia bigelovii)

Range

It grows only in the intertidal zone of estuarine salt marshes on both coasts of North America. On the west coast it occurs from Alaska to Nayarit, Mexico.

Notes

Although it often grows in pure stands, few people ever notice this plant, since most folks avoid the wet ground where it grows. But plantsman Jon Weeks, who studied it for more than a decade, enthusiastically promotes its merits. Almost all other true halophytes (plants that grow in salty soil) are perennial, probably because the metabolic rigors of dealing with saline environments makes yearly seed production difficult. But an annual must make seeds every year, and Salicornia bigelovii manages to devote up to 12% of its biomass to seeds. It is also one of the most extreme halophytes known—it can survive in water that has 5 to 6 times the salt concentration of sea water. It also requires salt water to thrive and reproduce; it wilts when it gets rained on.

Estuarine salt marshes are theaters of evolution since each marsh is an isolated island of saturated saline soil surrounded by dry land and sea. Along the desert coast of Sonora and elsewhere, each estuary has a unique ecotype (distinct genetic race) of pickleweed; these differ in such characters as plant height, seed size, and season of germination. Weeks can look at a plant in the lab and tell which estuary it was collected from.

This diversity will be valuable in domesticating pickleweed as a crop plant. The plant itself is of minimal utility for forage because up to half its dry weight is salt, though it might be used as fuel or diluted with other feed for forage. But the seeds have great potential. They are about N oil (fat) of very high quality. Different fractions of this oil are suitable for such varied uses as diesel fuel, lubricating oil, and margarine. The oil is more than half linoleic acid; an essential dietary fat for humans that does not contribute to heart disease. For these reasons pickleweed may become an economically viable crop, one that can be irrigated with sea water. If this comes to pass it will be both a blessing and a curse. Though we could increase food production by using thus-far-unfarmable coastal deserts, such agriculture would contribute to the destruction of coastal deserts all over the world.

Mark A. Dimmitt

The cucurbits, as they are called, number 750 species worldwide; most species are vines. The flowers vary from barely noticeable to large and conspicuous. The fruits range from small and dry to large and tasty; the latter include cucumbers, squash, and melons. Gourds are hard-shelled squash that are used after they dry.

Two genera of bees (Peponapis and Xenoglossa) are tightly associated with this plant family. Squash or gourd bees are more effective pollinators of cucurbits than most other bees. They seem to be holding their own under competition from introduced honeybees (which collect the pollen but are inefficient pollinators of these flowers), probably because squash bees are active earlier in the morning.

Cucurbita digitata

English names: coyote gourd, finger- leafed gourd
Spanish names: calabacilla (little squash), chichicayote, meloncillo (little melon), melón de coyote (coyote melon), calabaza amarga (bitter squash)

Description

The large, underground tuberous root produces several to many herbaceous stems as long as several yards (meters) in the summer. The stems typically lie flat on the open ground; occasionally they climb into surrounding vegetation with their tendrils. The palmately-divided leaves with very narrow lobes are widely spaced on the stems. (Cucurbita palmata is similar but has broader lobes; the 2 species intergrade in the western Sonoran Desert.) Vase-shaped, bright yellow flowers about 2 inches (5.1 cm) across open before dawn, and wilt by late morning. After pollination, female flowers develop 3-inch (7.5 cm) spheroid gourds, green with yellowish stripes when young, and maturing to straw-colored.

Coyote gourd (Cucurbita digitata)

Range

This species occurs from the lowest and driest desert elevations into desert grasslands, from southeastern California to southern New Mexico and into northwestern Sonora.

Notes

The fruit pulp contains toxic and extremely bitter chemicals that humans use to make soap; clothing laundered in it reportedly repels body lice. Humans eat the nutritious seeds which contain up to 35% protein and 50% fat. Coyotes, porcupines, and some other animals can eat the seeds even when tainted by the pulp. Javelina dig up and eat the bitter tuberous roots, which they can sniff out even when there is no vine above ground. People have used the gourds as containers since prehistoric times.

The modifier “coyote” is in the name of a number of Southwestern plants. Most often it identifies wild relatives of domesticated plants. In the mythology of the O’odham and other native cultures, Coyote (a spirit who often appears in the form of the animal of the same name) is, among his other attributes, a trickster and all-around rascal who makes a great deal of mischief. One of the things he does is ruin useful objects by defecating on them. That’s how the world got coyote gourds, coyote tobacco, and coyote passion flower, among others. The actual animal coyote marks its territory by defecating on conspicuous landmarks.

Buffalo gourd (Cucurbita foetidissima)

Cucurbita foetidissima (buffalo gourd) is a related species from higher elevations. It has a similar growth habit, but the leaves are large gray-furry triangles and have a rank odor when bruised. The starches from the very large root are edible after processing, and it is being developed as a potential feed crop. The seeds are a potential commercial source of oil.

Coyote gourd has a cool-season counterpart in Marah gilensis. It sprouts in early spring after winter rains and dies back to the huge root by the onset of the dry foresummer. During its brief season it produces a few very large seeds in each of its small, dry prickly fruits. Little else is known about the ecology of this plant.

Tumamoc globe-berry (Tumamoca macdougalii) provided an opportunity for the U.S. Endangered Species Act to work as it was intended. This diminutive plant, with a fist-sized underground tuber and wispy vines that grow and bear small red fruits during the summer rainy season, was thought to be very rare. When a population was discovered in the path of the Central Arizona Project canal during the environmental impact study, the species was quickly listed as Endangered in 1986. The Endangered Species Act funded surveys and ecological studies on the plant over the next several years. The studies revealed the Tumamoc globe-berry to be both common and widespread; it was rarely encountered simply because it’s difficult to see among the shrubs it climbs in, and few people had previously looked for it. The species was delisted in 1993.

Mark A. Dimmitt

Ephedra (Ephedra trifurca)

Ephedra spp.

English names: ephedra, joint fir, Mormon tea
Spanish name: canutillo (and several spelling variants)

Description

These woody shrubs grow 2 to 5 feet (0.6-1.5 m) tall and wide. The terminal stems are thin, green, and essentially leafless. These are conifers more primitive than pine trees; they bear papery cones. (Their closest relative is the bizarre Welwitschia spp. of the Namib Desert, which looks like a beached green octopus but has the same cone structure as ephedra.) The various species are similar in general appearance; distinguishing among them requires close inspection.

Range

About 40 species occur in arid habitats in the northern hemisphere and South America. About half a dozen occur in the Sonoran Desert region.

Notes

The stems contain caffeine and ephedrine (a drug that acts like adrenalin/epinephrin). The closely related pseudoephedrine is now synthesized commercially and is an ingredient in commercial asthma and cold remedies, e.g., Sudafed®. Pseudoephedrine is also a precursor in the production of the dangerous illegal drug methamphetamine (“speed”). A tea with stimulant properties is made by steeping dried stems. It has been used medicinally to treat a variety of ailments including syphilis, diabetes, and pneumonia. A Chinese species is the source of ma huang, a tea so potent that it has caused deaths from overstimulation of the heart.

In the Gran Desierto and Algodones Dunes ephedras grow much larger than usual; bushes 15 feet (4.6 m) across can be found. Occasionally a dune migrates away from one of these plants, exposing many feet of stems that had been slowly buried as the dune marched over it and the bush managed to keep a couple of feet of living stems in the sunlight. Observations of such blowouts suggest that these plants are very old, though they have not been documented to live more than about 50 years. We don’t yet know how long ephedras live; they have not been thoroughly studied by biologists.

Mark A. Dimmitt

The 8000 worldwide species of spurges are as ecologically diverse as the composites. They occupy most habitats and exhibit nearly every growth form used by plants. In fact, annuals, perennials, trees, succulents, C3, C4, and cam species can all be found in the single genus Euphorbia. Until recently this genus contained the little weedy spurges in our gardens, the spectacular Christmas poinsettia (which originated in tropical Mexico), and African succulents—some of which are nearly perfect mimics of the New World cacti. Now some taxonomists raise many of our species previously in a subgenus Chamaesyce to the genus Chamaesyce.

Euphorbia albomarinata

Recognizing such a diverse family by vegetative characteristics is virtually impossible. In most species the inflorescence is a cyathium, a single female flower with its distinctive 3-lobed ovary surrounded by a number of male flowers consisting of a single stamen each. The male cyathia may have colorful bracts that resemble petals (e.g., crown of thorns—Euphorbia milii), and some species have colored leaves that serve the same function (e.g., poinsettia, Euphorbia pulcherrima). In some species male and female flowers are borne on separate plants. A few genera produce more typical flowers with true sepals and petals. The poinsettia is one of the largest ornamental nursery crops; tens of millions are produced annually for the Christmas season. Other economically important examples include manihot (the source of cassava and tapioca) and castor bean (the source of the once-popular health remedy, castor oil).

Jatropha cardiophylla

English names: limberbush, dragon’s blood (both applied to several other species)
Spanish names: sangregado, sangrengado (contractions for dragon’s blood), torote, sangre de cristo (de drago) (Christ’s or dragon’s blood)

Description

Limberbush is a shrubby succulent to 3 feet (1 m) tall consisting of many usually unbranched stems arising from fleshy underground rhizomes. The branches are semisucculent and extremely pliable, and have smooth reddish bark. Bright green, heart-shaped leaves are present only during the brief summer rainy season. The flowers are tiny whitish bells that appear during the rainy season. (This genus has “normal” flowers with petals.)

Limberbush (Jatropha cardiophylla)

Range

South-central Arizona and most of Sonora below 4000 feet (1200 m) elevation.

Notes

This is the northernmost North American Jatropha, a worldwide genus of 170 mostly frost-sensitive tropical species. The above-ground stems are succulent, but much of its biomass is in the massive underground roots, which can produce new stems quickly after being killed to the ground by periodic severe freezes. Coral bean (Erythrina flabelliformis) has a similar growth form in the north end of its range where it is occasionally killed to the ground by both frost and fires. Limberbush shares with ocotillo the trait of having both long shoots that produce stems, and short shoots at each original long-shoot leaf; the latter produce leaves periodically without sprouting new branches. The pollinator is a rare tiny fly.

Limberbush heralds the arrival of the summer monsoon. The increased humidity associated with this seasonal wind shift induces leaf production within a week or so. The leaves remain small until the first rain provides the moisture for their full expansion. The leaves turn yellow and fall soon after the air dries out at the end of the monsoon.

The O’odham use limberbush extensively in basketry. It is a widespread toothache treatment.

Jatropha cuneata grows in the driest of desert subdivisions. Its many stems arise from a very short trunk.