Mark A. Dimmitt

Behind the formidable appearance of agaves and the plants formerly grouped with them is a wealth of uses. They have long been and still are used extensively by indigenous peoples throughout North and Central America for food, fiber, and medicine. The roasted, sugar-rich agave hearts have been an important food for numerous Native American groups. Juice from the mature plants is consumed both fresh and fermented. Fermented liquid from the cooked heads is distilled into mescal. Tequila, the best-known variety of mescal, is distilled from one species, Agave tequilana. The tequila agave (mezcal azul) is a significant economic crop in southern Mexico; North Americans alone consume more than a million gallons of tequila a year.

Fiber from the leaves of Agave sisalana is the source of sisal rope, and A. fourcroydes yields henequen fiber. Sisal is a major economic product widely cultivated in Africa, Asia, as well as in the New World; it provides 70 percent of the world's hard, long fiber for ropes, rugs, and bags in recent decades. Numerous native American peoples weave baskets from the fibers of yuccas and nolinas.

The complex chemicals in this family have many uses. Compresses for wounds have been made from macerated agave pulp, and juices from leaves and roots were used in tonics. But beware-sap from many agaves can cause severe dermatitis. The juice of the more virulent agaves has been used as fish poison and arrow poison. Agaves and yuccas are used in Mexico to make soap. Yuccas were once used to provide the foam of root beer and are still used in livestock deodorant. More recently steroid drugs have been synthesized from extracts of several species in the family.

Today these plants are appreciated for their beauty and are widely used to add accents to landscape designs and mark property boundaries all over the world. Howard S. Gentry's book Agaves of Continental North America was so popular that it was reprinted in 1992, an unusual event for a botanical monograph.

As originally described by Gentry, Agavaceae consists of 18 genera and a little over 400 species, many of them native to western North America. This family is difficult to define; it has been revised by taxonomists several times in recent years.

Agaves, yuccas, and relatives were once included in the very large lily family Liliaceae. Gentry segregated agaves, yuccas, and other genera into their own family Agavaceae in the 1970s. More recently other botanists have split the old Liliaceae into many more families and removed some genera from Agavaceae, among them Nolina, Dasylirion, Sansevieria, and Dracaena. Whatever their taxonomic status, these are highly useful plants with dramatic forms.

Genus Agave

English names: agave, century plant

Spanish names: mezcal, mescal, maguey, amole (general names that vary by region and use of the plant)

Agaves are among the most conspicuous plants of arid North America; their bold forms attract attention in any landscape whether natural or designed. All are characterized by succulent or semisucculent leaves that form rosettes from a few inches to several feet across, but there are many variations on this basic pattern. Most species are essentially stemless but a few grow trunks that creep along the ground. Some species have only one rosette; most multiply by underground suckers and may develop into large colonies. Agave leaves vary from green through bluish to silver-gray, and are often strikingly banded with different shades of color. Leaves range from long and narrow to short and broad, and from arrow-straight to gracefully recurved or haphazardly twisted. The leaf margins are typically lined with large, sharp spines (teeth) and each leaf is usually tipped with a hard, sharp spine. A few species have leathery, unarmed leaves. The leaves are so tightly compacted in the growing tip that the teeth leave imprints on both surfaces of adjacent leaves after they unfurl, overlaying their own complex patterns over the banding. These imposing features make agaves popular among succulent collectors and landscape designers.

Various agave species have also been and continue to be important sources of food, fences, rope, medicine, and liquor. The Mescalero Apaches were named for their dependence on this plant. Before them the Hohokam cultivated agaves as a major food crop (see A. murpheyi).

Agaves flower on tall, branched or unbranched stalks that grow from the center of the leaf rosette. As a plant approaches maturity at 10 to 30 years of age it accumulates a great quantity of sugar and starch in the heart tissue. These carbohydrates provide the energy that fuels the rapid development of the inflorescence (the flowering structure, including supporting stems), which is usually massive compared to the plant that produces it. In all but a few species the rosette dies after flowering and fruiting, having spent all of its life energy to produce a huge quantity of seeds-a monocarpic (once-fruiting) life cycle. The plants literally flower themselves to death.

Though the flowering rosette usually dies, many species produce vegetative offsets (suckers or pups in English, hijos or "sons" in Spanish) before or after flowering. In this way clones (multiple, genetically identical, individuals that originated from a single original seed) form colonies that may persist for centuries or longer.

Range

The genus ranges from Utah in western North America through Mexico (where the most species are found), with a few in northern South America and on Caribbean Islands. The majority of agave species occur in semiarid habitats above the desert, especially in desert grasslands and oak-pine woodlands. About 40 of the 150 North American species occur in the Sonoran Desert region.

Ecology

Agaves typically grow on well-drained, rocky slopes. Different species are adapted for pollination by insects, nectar-eating bats, and hummingbirds. Seeds are dispersed by wind, usually only a short distance from the parent.

The two major groups, or subgenera, of agaves are distinguished from each other by whether their inflorescences are obviously branched or not. Most species in the subgenus Agave (branched inflorescences) developed features that enable them to be pollinated by nectar-feeding bats, although other pollinators may currently be more important. They grow whitish to yellow flowers which produce copious nectar and pollen at night. Bats are attracted by the fragrant nectar, which usually smells unpleasant to humans-like ammonia or rotting fruit, depending on the species. Agave nectar and pollen are major food sources on the northernmost and southward legs of the bats' migratory routes. After wintering in the Mexican tropics, bats migrate northward through the desert following the south-to-north wave of spring-blooming columnar cacti. They raise their young in southern Arizona, then return south via the mountains, feeding on agaves. Hawk-moths are also common visitors to the night-flowering agaves and are probably effective pollinators; bees and other diurnal insects aid in pollination as well.

Some species in the subgenus Agave occur outside the range of the bats, or flower at a season when the bats are not present. These have colored diurnal flowers that are pollinated by hummingbirds and bees. Species in the subgenus Littaea (which bear unbranched spikes) are pollinated mainly by insects and sometimes hummingbirds.

Of the 40 or more agaves in our region, several are ecologically or horticulturally important. Agave americana, a very large plant with rosettes up to 12 feet (3.7 m) broad, is by far the most commonly used in gardens in the southwest U.S. and worldwide, although most of its natural range is outside the Sonoran Desert region. In our species accounts, we focus on some of the more interesting local species.

Ethnobotany

Several beverages are made from the sugar-rich juices of mature agaves. The extracted juice is drunk fresh as aguamiel (honey-water) or fermented into pulque; both are popular beverages south of the Sonoran Desert. Steamed heads or central stalks are mashed and allowed to ferment with added liquid. After several days, the resulting fluid is distilled into the potent liquor mescal. The most widely known local ("bootleg") variety of mescal is Bacanora, named after that Sonoran town and made from Agave angustifolia. Other varieties of bootleg mescal are made in nearly every Mexican village within agave habitat. Tequila, the most famous legal variety of mescal, is made from the single species Agave tequilana, grown near the town Tequila in Jalisco. Tequila is to mescal much as Chardonnay is to wine.

Mature agaves also provide food. The leaves are cut off near their bases, leaving a cabeza ("head") resembling a giant pineapple, weighing up to 70 pounds (32 kg). The cabezas are usually pit-roasted in large numbers and eaten during fiestas. (Note: The raw flesh of many agaves is caustic and can even blister skin.)

English name: desert agave
Spanish name: amul

Description

This is a small species with rosettes rarely over 1¼ feet (0.5 m) in diameter. The leaves are nearly straight and light gray to bluish-gray, with marginal teeth. Most varieties sucker near the base to form dense colonies, but some offset by long underground rhizomes, and a couple of forms rarely offset at all. The branched inflorescence bears bright yellow flowers that are attractive to hummingbirds. Some populations have red buds, which contrast beautifully with the flowers.

Range

One of the most desert-adapted agaves, it is native to rocky or gravelly soils in the Lower Colorado River Valley subdivision of the Sonoran Desert. Its range extends barely into Arizona Upland and the Mohave Desert.

Comments

Agave deserti is a very slow-growing species; even in cultivation with generous irrigation it takes at least 20 years to flower. As spent rosettes of wild plants die and decompose, new ones replace them on the outer margin, eventually forming ring-shaped colonies. Rings 20 feet (6 m) in diameter in California's Anza-Borrego Desert State Park may be more than a millennium old. One of the more edible agaves, Agave deserti has been extensively harvested by desert peoples.

In Baja California this species can be confused with the straight-leaved varieties of Agave cerulata, which also grows in extreme desert habitats. Agave chrysantha is larger with golden-yellow blossoms; it descends into the higher elevations of Arizona Upland in south-central Arizona. This is the most frequently-encountered agave on the northeastern boundary of the Sonoran Desert north and east of both Phoenix and Tucson.

Agave murpheyi

English name: Hohokam agave, Murphey's agave
Spanish name: maguey (a general name for many agaves)

Description

This agave consists of freely suckering rosettes to 3 feet (1 m) across of narrow, straight, toothy light-green leaves. It rarely sets seeds, but produces many plantlets (also called bulbils and semillas, or "seeds") on the flowering stalk.

Range

Only a few populations are known in southern Arizona and northern Sonora. Comments The origin of this agave is unknown; all of the populations are associated with ancient Indian sites. It was extensively cultivated for food and fiber by the Hohokam Indians. They planted this species in the desert (and A. delamateri at higher elevations) along low rock check-dams built on bajadas to slow runoff and increase water penetration. Hundreds of thousands of acres of habitat were modified in this way before the Hohokam culture dispersed 800 years ago. The check-dams and associ-ated roasting pits and agave harvesting tools are still abundant, and in a few sites colonies of the agave survive to this day. All of the populations from Caborca, Sonora, to New River, Arizona, are so similar that they may be one genetic clone. Proof of this would further substantiate the plant's cultural dispersal as one of the few domesti-cated north of Mesoamerica.

English name: shindagger
Spanish names: amole, maguey, amolillo

Description

The narrow, straight leaves-up to a foot (30 cm) long in small rosettes-have no marginal teeth, but are very sharp-tipped, hence the English vernacular name. Shindagger suckers profusely to form dense colonies that sometimes merge with others and cover many acres (hectares). The inflorescence is a narrow spike 6 to 8 feet (2-2.4 m) tall, bearing long-tubular, fragrant yellow flowers.

Range

It grows in southern Arizona and northern Sonora, mostly in desert grassland and oak habitats and often on steep, rocky slopes. It is occasionally found in Arizona Upland, e.g., near the summit of the Tucson Mountains.

Comments

There are several other small agaves that may be confused with this species, especially A. felgeri, A. toumeyana, A. polianthiflora, and A. parviflora. The last two are only half as large as A. schottii; A. polianthiflora's flowers are pink to red, while the other 3 have shorter (less than 1¼ inches, 30 mm) flowers.

English name: none
Spanish name: mescal pelón (bald agave)

Zebra agave (Agave zebra)

Agave pelona

Agave zebra

English name: zebra agave
Spanish name: none

Description

Agave pelona: The dense rosette of narrow, toothless leaves is dark blue-green or yellow-green, 2 to 4 feet (0.6-1.2 m) across. A long reddish spine tips each leaf. Since they do not cluster, the singular rosettes are very symmetrical. The flowers are an unusual deep reddish-purple; they're borne on a tall, unbranched spike in the spring.

Agave zebra: These rosettes-3 to 4 feet (1-1.2 m) across-do sucker. The light gray, strongly silver-banded and spine-imprinted leaves are stiff, channeled (folded into a "V"-shape in cross section), and usually strongly recurved. The grayish flowers are borne on a tall, narrow main stem (panicle).

Range

These two species are described together partly because they are both narrowly endemic to the Sierra del Viejo and Cerro Aquituni southwest of Caborca, Sonora. They grow intermingled on steep limestone slopes, where their different growth forms contrast dramatically.

Comments

The other reason these two are grouped is because they share similar past and present uses. Apparently neither species was much harvested by local peoples for traditional ethno-botanical uses. But their rarity and beauty has given both of them value in the new ethnobotany of aesthetic horticulture, where their popularity increases among succulent collectors.

Genus Yucca

English names: yucca, Spanish bayonet

Spanish name: palmilla

Yuccas are usually easy to distinguish from agaves even when out of flower. Like all members of the family, they bear leaves in rosettes. But yucca foliage is only semisucculent or nonsucculent and the leaves are usually straight; many species grow trunks. When in bloom, all are easily recognized by their large, white, fleshy, bell-shaped flowers. Unlike most agaves, most yuccas are polycarpic (blooming more than once).

Range

Like agaves, most yucca species occur in semiarid habitats above the desert. Habitats range from the northern Great Plains through woodlands and the dry tropics of Mexico. One species occurs in the southeastern U.S. and the West Indies. About 10 species occur in the Sonoran Desert region.

Ecology

Yucca pollination ecology is an example of a tight symbiosis called a mutualism. (Symbiosis refers to a close association between two species in that at least one benefits from the association. Mutualism is a symbiotic relationship in which each species depends on the other for survival.) With only one exception, yucca reproduction depends on moths (genera Parategiticula, Tegiticula) which deliberately cross-pollinate the flowers. (Yucca aloifolia of the southeastern U.S. is pollinated by bees.) The blossoms need pollen from a different plant in order to produce seed, and it must be packed into a deep receptacle on the stigma, an event that could not occur by chance visitation. The moth is equally dependent on the yucca. It lays eggs on each pollinated ovary, and the hatched larvae eat some of the developing seeds. Biologists have only recently determined that almost every species of yucca has its own species of yucca moth; some yuccas have two moth species. Such a tight mutualism has risks for both partners. Emergence of adult moths must coincide with yucca flowering for the reproductive needs of both species to be met. However, the synchronization of moth emergence with flowering is frequently poor and seed set and moth reproduction in such years are low. Furthermore, yucca populations may flower sparsely or not at all in dry years. Yuccas don’t have to set seed every year because they flower many times in their long lives. The yucca moths employ a survival strategy analagous to that of desert annual plants. The full-grown larvae exit the ripening yucca fruit and burrow into the ground, where they enter a deep dormancy (diapause). Like the seeds of many annuals, only some of the larvae will metamorphose and emerge as moths in the following flowering season. The rest remain in diapause for two or more years.

Ethnobotany

Yucca flowers and fruits are edible fresh or dried. Chemicals in the roots of some species are used to make soap. (The Spanish name amole is applied to a number of unrelated plant species from which soap is made.) The roots of Mohave yucca (Y. schidigera) were used to provide the foaming agent in root beer, and the stems are still (over-) harvested to produce livestock deodorant.

Yucca arizonica (formerly Yucca baccata spp. arizonica)

English names: blue yucca, Spanish bayonet, Thornber yucca
Spanish names: dátil (date), palma criolla (creole or native palm)

Description

A variable semisucculent species, this yucca usually occurs as dense clusters of stems to 8 feet (2.5 m) tall, tipped with rigid bluish to yellowish leaves. The lower half of the wide inflorescence is typically concealed within the leaves.

Blue yucca (Yucca arizonica)

Range

From the Sonoran Desert into oak-pine woodland, southern Arizona to central Sonora.

Comments

It was formerly considered a subspecies of banana yucca (Y. baccata), a more widespread, usually stemless or recumbent species. Its roots are used for red fiber in Tohono O’odham baskets.

Yucca elata

English names: soaptree yucca, soapweed
Spanish names: palmilla, palmito, soyate, cortadillo

Description

The soaptree yucca has a simple or branched trunk up to 23 feet (7 m) tall. The numerous 2-foot (0.6 m) long, thin, flexible leaves are clustered at the ends of the stems, making the plant appear somewhat like a palm. Flowers are creamy white, borne in a great cloud on the upper half of a stalk up to 10 feet (3 m) tall, usually in May and June.

Sopatree yucca (Yucca elata)

Range

Soaptrees grow mainly in desert grassland from central Arizona to west Texas and northern Mexico. The range extends into the upper margin of Arizona Upland.

Comments

The leaves yield the major basketry fiber for the Tohono O’odham, who know how to harvest the tender new leaves in a way that promotes branching instead of killing the plant. The English common name refers to another of its uses.

Hesperoyucca whipplei (formerly Yucca whipplei)

English names: Spanish bayonet, our Lord’s candle, chaparral yucca
Spanish names: sotolillo, lechuguilla, quiote

Spanish bayonet (Hesperoyucca whipplei)

Description

The bluish-green rosette 3 to 6 feet (1-2 m) in diameter consists of about a hundred long, narrow, and dangerously rigid, sharp-tipped leaves. Rosettes are single to multiple in different subspecies. The inflorescence rises well above the leaves, usually about 8 feet (2.5 m) tall in the desert forms, bearing dense masses of creamy-white flowers (tinged with purple in some populations). The flowering rosette dies, so the nonclustering subspecies are monocarpic.

Range

This plant is primarily a chaparral species of the Californias, with a few desert populations in the Lower Colorado River Valley and gulf side of the Baja California peninsula. The desert form is usually about 3 feet (1 m) in diameter and nonclustering.

Comments

This species was recently removed from the genus Yucca because it was determined to be only distantly related. Its pollinating moth is also distinct.

Nolinaceae (formerly Agavaceae), nolina family

Dasylirion wheeleri

English name: desert spoon
Spanish names: sotol (sotole is a palm), saño

Description

This perennial evergreen consists of a rosette of hundreds of long, narrow leaves armed with small, sharp, marginal teeth. The rosettes are usually stemless and about 6 feet (2 m) across. Old specimens may develop trunks to 6 feet (2 m) tall, and these sometimes branch. Sotols are dioecious (producing only male or only female flowers on each plant). The inflorescence emerges from the center of the rosette in early summer and grows to 12 feet (3.7 m) tall. Its numerous, dense branches bear thousands of tiny, green- or violet-tinged whitish flowers, followed by winged fruits on female plants. Desert spoon does not die after flowering. The stem branches at the base of the inflorescence and continues growing.

Desert spoon (Dasylirion wheeleri)

Range

Desert spoon grows on rocky hillsides and slopes at 3000 to 6000 foot (900-1800 m) elevation in southeastern Arizona, southwestern New Mexico, northern and eastern Sonora, Mexico, and to west Texas. Despite its English name, it is primarily a grassland species that extends into the desert.

Comments

The rosettes flower only once in several years. Blooming plants attract huge numbers of insects, including flies, bees, wasps, and butterflies. Until a few decades ago, the Tohono O’odham wove beautiful sleeping mats by plaiting together sotol leaves after removing marginal teeth from the leaves.

Genus Nolina

English names: nolina, beargrass
Spanish names: yuca, sotol, palmita

Nolina (Nolina bigelovii)

Nolina bigelovii is the common northern Sonoran Desert species of this genus; it has no vernacular name, save that borrowed from its botanical name— “Bigelow nolina.”The similar N. beldingii occurs in Baja California; you can probably guess its vernacular name. Both resemble desert spoon (Dasylirion) with no marginal teeth on the leaves. The yellowish- to bluish-green rosette of nonsucculent foliage begins at ground level and in an old plant may top a 6 foot (2 m) branched trunk. The tall, densely-branched inflorescence bears thousands of small whitish flowers. But the overall appearance is a greenish plume, drying to an equally attractive straw color.

Comments

The Coahuila Indians ate N. bigelovii flowering stalks after roasting them in pits.