D e s e r t E x p o s u r e
January 2012
Southwest Wildlife
The Noble Agave
The plant that gives us mescal and tequila also bestows a literally once-in-a-lifetime blooming display, when the agaves flower themselves to death. Named after the Greek term for "noble," the agave, with its distinctive rosette, or spray-like, arrangement of succulent leaves, bears a clear resemblance to its botanical relative, the yucca.
Story and Photos by Jay W. Sharp
Like the yucca (see "The Giving Tree," December 2011), the agave serves as a food and material resource for various animals. But the agave, unlike the yucca, also yields raw stock for several potent beverages that give a whole other dimension to the notion of nature's "food chain."
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The century plant approaching full bloom. |
The agaves, which include more than 200 species, evolved, like the yuccas, in the New World. Their range extended from southern Nevada and southern Utah across our Southwestern deserts down through Mexico and Central America and across into Caribbean islands. Since the 15th century, their range has expanded across the Atlantic, propelled primarily by the Europeans. For instance, I have seen the Agave americana — the classic "century plant" — growing in Algeria, a former French colony, in village gardens near the Mediterranean coast.
More than a dozen species of agave grow in the Southwest, especially in the desert grasslands of the basins and in the wooded foothills of the mountain ranges. They seem to prosper on slopes that have slightly acidic soils and a rocky overburden.
The typical, relatively massive agave leaf, with its stiletto point and wickedly barbed edges, would serve as a weapon for Conan the Barbarian. The typical Southwest yucca leaf, by comparison, with a more rapier-like shape and mere filaments along its edges, would better serve as a weapon for Zorro.
In some Southwestern species, an agave leaf rosette may span perhaps a foot and a quarter; in others, several feet. The leaves' rosette arrangement and channel shapes serve to funnel rainwater to the heart of the plant. The leaves range in color from green to grayish green to bluish green and often bear decorative bands in various shades of green and brown. They vary in shape from short and thick to relatively long and narrow, with some laser-beam straight, others elegantly recurved, and still others inelegantly twisted and bent. Sometimes leaves bear imprints from the tight clasp of neighboring leaves before their rosette fully unfurled.
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The agave leaf’s stiletto-like point. |
The agaves' leaves, according to John Moore of the Colorado State University Cooperative Extension Demonstration Garden, have special cells for water and food storage. In fact, he notes, "All the water storage and energy storage of the plant is in the leaves." Like yuccas, the agaves — in a botanical strategy designed to minimize water evaporation — open their stomata (leaf pores) during the coolness of night to gather the carbon dioxide they will need for photosynthesis during the sunlight of the following day.
Most agaves have a very abbreviated stem. Indeed, the leaf rosette for those species almost seems to spring directly from the roots. (Some yucca species — our Lord's candle, for instance — have little or no stem, but various others such as the torrey, soaptree and Joshua tree yuccas often have stems that range from 10 to 20 feet or more in height.) Some agave species produce small plantlets — clones sometimes called "pups" — from their abbreviated stems, at the base of their leaf rosettes. "In this way," according to the Arizona-Sonoran Desert Museum, "clones (multiple, genetically identical, individuals that originated from a single seed) form colonies that may persist for centuries or longer."
The agaves, like some yucca species, have shallow, fibrous, radiating root systems that race against competing plants' root systems as well as high evaporation rates to capture as much water as possible from the desert's infrequent rainstorms and snow melt.
An agave, unlike a yucca, spends years, often decades, accumulating water and carbohydrates in its heart, preparing for a seminal and life-ending event — the botanical ritual of blooming. When it matures, having stored sufficient resources, the agave begins to flower, producing its blossoms during the summer and early fall. According to the Arizona-Sonoran Desert Museum, "The 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…. The plants literally flower themselves to death."
In their closing days, memorialized by white to yellowish white to orange or greenish blossoms, some agave species flower during the day, inviting hummingbirds as well as bees and other insects to feed on an abundant reservoir of nectar in return for the critical service of pollination. Other species flower during the night, attracting not only hawk-moths and other nocturnal insects, but also long-nosed bats, with a banquet of foul-smelling nectar, receiving payment by way of pollination. Indeed, according to the Smithsonian's National Zoological Park website, "An estimated 100,000 lesser long-nosed bats… converge on southeastern Arizona in late summer for the agave bloom, and an even larger number feed on agaves not far south, in the Mexican state of Sonora. These gray and cinnamon-brown creatures are valuable pollinators of the cacti and agaves they frequent."
Family Members
Like other desert succulents, especially the prickly pear cacti, the agaves almost seem to take a perverse delight in confounding taxonomists — the scientists who would classify and name the plants. As far back as 1871, Sir Joseph Hooker, a famed English botanist, remarked that the agave species were "difficult to name accurately." Authority Jan Kolendo, who quoted Hooker in "Issues of Agave Nomenclature," published on the Globalnet website, added, "The confusion continues to this day…. There are so many unresolved issues that agavologists will be kept busy for some time to come." The agaves confuse the "agavologist" still further because they have migrated so much in the company of both prehistoric and historic man that biological scientists sometimes have trouble tracing individual species back to their origins.
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Patch of lechuguilla or shindagger agave, located in Anthony Gap, between the Organ Mountains and the Franklin Mountains. |
A few of the more notable agaves in our region include the mescal agave (Agave neomexicana), the lechuguilla or shindagger agave (Agave lechuguilla), the desert agave (Agave deserti), and the classic century plant (Agave americana).
The mescal agave, especially common in southwestern New Mexico, grows in grasslands and on limestone shelves up to several thousand feet in elevation. A small- to medium-sized, tough and resilient agave, it produces numerous pups. Like most other agaves, the mother plant dies once it has bloomed. The mescal agave was an especially important food source for the Mescalero Apache, whose name comes from the plant.