The genus Agave has approximately 200 species in it, almost all of them from North America, and especially Mexico, which is the center of diversity for these plants. There is a great variety of leaf shapes, colors, and sizes, but there are relatively few green agaves with wide leaves. (Most are wide and blue, or narrow and green, or some other combination.) One of these is the sizable cow horn agave, A. bovicornuta, which inhabits steep rocky canyons and mountains in the Mexican states of Sonora, Chihuahua, and Sinaloa. The Spanish name for it is lechuguilla, meaning “little lettuce”, which must be some sort of ironic appellation because there’s not much that is lettuce-like about these plants. Lechuguilla is also a common name applied to certain other agaves, including the Latin name of Agave lechuguilla applied to a widespread but much smaller plant with narrow leaves that grows abundantly in the Chihuahuan Desert farther east. But this is one of the largest and greenest of agaves, reaching dimensions of 5 or more feet tall and wide before commencing with flowering.
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Agave bovicornuta, aka cow horn agave in English and lechuguilla in Spanish, is shown here growing in a canyon on the Sierra de Los Alamos above the historic colonial town of Alamos, Sonora, Mexico. They are generally mid- or higher elevation plants, doing best between elevations of 3000 and 5000 feet (900 and 1500 meters).

The habitat of Agave bovicornuta: Where the Sierra Madre Occidental rises to 4000 feet (1200 meters) and above along the Sonora/Chihuahua border region in northwestern Mexico. The forest here is seasonally dry and a mixture of tropical thorn scrub at lower elevations with oak-pine woodland starting to dominate in the higher reaches.

The juvenile rosettes of A. bovicornuta are often very attractive, with strong marginal teeth and bold leaf imprints.

Cow horn agaves have undergone a limited amount of genetic selection via the horticultural trade in the USA. Breeders have tended to favor clones with the strongest and reddest teeth, and put them into tissue culture to propagate thousands of genetically identical plants for the domestic nursery trade.

In cultivation, A. bovicornuta survives light to moderate freezing down to about 25 F (- 4 C) without trouble, but it does tend to suffer leaf damage much below that and should be covered if it gets to or below 20 F ( -6 C). They can tolerate full sun in lower Sonoran Desert conditions in summertime if they receive regular watering, although they look significantly better in afternoon shade, since extremely hot temperatures tend to make the leaves bleach to a paler yellowish color. Sometimes the leaves can develop dead white or brown patches during excessive heat, although if sunburn can be avoided the bleached yellow color usually returns to normal green in autumn once the weather cools down. The agaves below are being shaded by a juniper tree (Juniperus californica) in my garden in Yucca, AZ. Clockwise from the front: A. bovicornuta, A. parryi, A. ocahui, and A. ferdinand-regis to the right; also, A. utahensis can be seen in the rear left corner.

This canyon in the Sierra de Los Alamos of far southern Sonora, Mexico gives a hint at how steep and rugged the terrain that Agave bovicornuta favors is. The Sierra de Los Alamos is quite biologically diverse, and much of the mountain range and surrounding foothills has been declared a nature preserve, although traditional uses such as ranching are still allowed. Jaguars live here, alongside many other large animals, tropical birds such as military macaws, and rare plants in this relatively ecologically intact region.

One succulent associate often found in conjunction with cow horn agaves is the Alamos barrel cactus, Ferocactus alamosanus. It’s amazing how little soil the barrels require to grow, clinging to sheer rock faces and wedged into narrow cracks.

The rugged slopes of the Sierra de Los Alamos are home to this nearly blooming-size rosette of A. bovicornuta, shown here in a dry and dormant late spring phase prior to the arrival of the annual summer monsoon season in late April 2017. The deciduous plants are mostly leafless, and the tropical thornscrub awaits the rains, which won’t come for at least another 6 or so weeks, not until mid-June or so.

Northern Mexico is a global center of diversity not only for agaves, but also for both oak (Quercus) and pine (Pinus) tree species. Each of these three families has dozens of representatives in this region, to the extent that it virtually constitutes a uniquely recognizable botanical association that covers thousands of square miles, and is distinct from other similarly recognizable types of plant associations in other ecosystems elsewhere.

Agave bovicornuta is generally a single-rosette species that does not propagate reliably from vegetative offsets, unlike many of their brethren. Since the rosettes bloom just once and then die, this makes them dependent entirely upon seed reproduction. Below, a cow horn agave flower spike sets fruits about half-sized from what they might be at full maturity, as withering yellow floral remains cling to the tips of the pods.

Livestock such as cattle and goats seem not to find the agave leaves themselves very palatable, and tend to avoid eating them unless there is some exceptional drought or overgrazing causing a lack of other food options. But the flower spikes themselves are quite edible, since they are free of hooked teeth and are filled with sugars being mobilized by the plant as it puts all of its resources into the one-time blooming process. Animals will push the rosettes over and decapitate the flower spike, thus preventing blooming. The spike shown above had only a couple of intact branches with seed pods left behind, with most of the flowers having been chewed off, probably by cattle in this case. Below, you can also see where they ate some of the leaves, which would also have been sweeter than usual due to the sugars of flowering. Since this and certain other agaves are entirely dependent upon seeds for the continuation of the species, this type of grazing pressure can cause long-term population declines if not enough plants are able to produce the requisite seeds.

Fortunately many cow horn agaves do appear to be able to survive the depredations of domesticated livestock, due partially to their proclivity for living on steep rocky slopes where animals can’t easily reach either the vulnerable seedlings or the flowering adults. That said, many single-rosette, non-clumping agaves have probably suffered serious population losses in much of Mexico as a result of animals preventing the blooming process and concomitant seed set. The prickly pear cactus flower is Opuntia scheeri.

I hope you’ve enjoyed this glimpse into the life of the beautiful cow horn agave, and might consider growing one of your own. As I have here in Arizona. 🙂