There are about 30 or so different Agave species and subspecies in the United States, with 21 of those occurring in Arizona, which has the most taxa of any state. While all agaves have some drought tolerance, many of them are not truly desert plants and instead inhabit semidesert grasslands or shrublands, with some being borderline montane species even occurring at middle and higher elevations amidst trees in forested zones. Of those true desert species, the one that is arguably the most heat and drought tolerant is Agave deserti ssp simplex.

This photo shows the habitat of Agave deserti ssp simplex at the base of the southwestern Hualapai Mountains in Mohave County, Arizona. You can see the icy blue rosettes of the plants scattered amidst the granitic boulders here.

Agave deserti ssp simplex is a subspecies of the equally drought-resistant Agave deserti ssp deserti, which is the one found growing abundantly in the foothills of the mountains rising above Anza-Borrego Desert State Park in Riverside and San Diego Counties, California. The subspecies deserti also extends farther south into Baja California, Mexico. The habitat of those foothills is in many places similar to this, with large complexes of stacked granitic boulders rising along the shoulders of steep hills.

Agave deserti ssp simplex is so named because of the relatively solitary nature of the eastern and northern plants found in the Sonoran and Mojave Deserts. While they do form some offsets, those pups tend to be present in small numbers, and not in the massive clumps composed of dozens of heads found in ssp deserti in Anza-Borrego. Singular plants are quite common and comprise maybe 25% to 35% of the population, with the remainder tending to have one or several pups, sparingly distributed nearby.

Obviously those populations in the eastern parts of the Sonoran Desert in Arizona will have saguaros (Carnegiea gigantea) growing nearby as floral associates. Since wild saguaros do not grow in California outside of a few stands along the Colorado River right on the border with Arizona, the presence of saguaros with A. deserti should in most cases indicate that it is ssp simplex that is being seen. And again, the singular or sparsely clumping nature of most plants would tend to support that same conclusion.

Ocotillos (Fouquieria splendens) are another plant associated with A. deserti simplex in the Arizona subsections of the Sonoran Desert, although since both are also found in the western subsections in California, they cease to be as useful as a diagnostic tool for determining where a given photo might have been taken. Below, you can see the dark brown residue of old, decayed rosettes several feet away from the currently living ones. Since individual rosettes may take anywhere from 20 to 40 years to reach blooming size, and the dry climate retards decomposition, it can be surmised that this set of live and dead agaves may be well over a century old, and possibly several.

I hold a dried scat produced by one of our native Sonoran desert tortoises (Gopherus morafkai). This rugged landscape of broken hills and  scabrous vegetation is actually pretty decent habitat for desert tortoises, since the terrain offers a variety of vegetation options for food, and as importantly, both temporary sheltering spots as well as sites for permanent long-term burrows.

Here in the Dutch Flats area south of the town of Yucca, Arizona where I live, there are actually more widespread populations of Agave deserti ssp simplex on the flatter areas amidst the Joshua trees (Yucca brevifolia ssp jaegeriana) than there are on the rocky hillsides. Other plant associates in this biotic community are ocotillos and palo cristi trees (Canotia holacantha).

There are some preliminary indications, inspired by new techniques of DNA analysis, that Agave deserti ssp simplex should perhaps be separated and elevated to become its own true species. If that ends up being the case, then the new name would turn into Agave simplex. Research is ongoing by several experts in the Agave genus, but if/when this becomes valid, we will report it here. Hopefully.

Agave deserti simplex is generally considered to be a somewhat medium-sized plant (when compared to the rest of its cousins), with most rosettes being between 18 and 30 inches in diameter (45 and 80 cm) at maturity. Some rosettes might be either larger or smaller at flowering size, but the vast majority are around this large when they do decide to bloom.

This is a fairly large rosette of about one meter across, somewhat bigger than typically seen. It will likely bloom fairly soon, although the central conical bud doesn’t show any signs of that yet in this photo. But they rarely get any bigger than this before flowering.

As with any seed-grown plant population, there is some individual genetic variation between the appearance of different clones. Some have relatively few marginal teeth along the leaf edges, while others have strong and very hooked teeth. The majority of rosettes are some shade of bluish-white, but there are greenish-white, rather green, and very blue forms as well. They all add visual interest to this already appealing species.

 

 

As with almost all other agaves save for a handful of species, Agave deserti simplex blooms only once in its lifetime, and the rosette doing so dies afterwards. Flower spikes usually initiate in the springtime between early March and early April, bloom in late May and June, and set ripe seeds by August. Capsules usually open partially once dry and start scattering their flat, black seeds to the wind, although some capsules retain at least some of their seeds for many months, often well into the next year.

 

 

At one point my friend Ron and I discovered an agave that had somehow become uprooted and toppled over. It was a dead flower stalk growing on the banks of a small wash channel, so possibly it was undermined via water erosion and tipped over, taking two firmly-attached pups with it. Knowing that the two semi-mature pups didn’t have a future unless they were replanted, we took it back towards the vehicle for salvaging.

It was too big to fit into the back of the vehicle easily, so we left it at a place where I could readily find it again. A few days later I returned with a shovel and replanted it in a smaller drainage channel, where runoff would water it naturally, but where erosion wouldn’t enable a repeat of the tipping over. Good deed done for the day.

I will close out this portfolio on Agave deserti ssp simplex with a photo progression on an individual plant that used to live in my garden between 1999 and 2007. Originally a salvage plant from a new roadway easement in the development I live in, I planted the mid-sized rosette in my garden, where it established and grew successfully for about 8 more years. In mid-March 2007, I noticed the conical bud was parting its leaves, indicating that it was entering the final phase of its existence.

 

 

By the first week of April, only about three weeks later, the agave spike had grown enormously to over 6 feet/two meters tall. Agave flower spikes grow amazingly quickly. In the so called “asparagus phase” of their development they often add 4 to 6 inches of height every single day. You can practically sit down and watch them grow from one hour to the next, quite literally.

By late April, less than two months after I first saw it emerging, the flower spike has reached it nearly mature height of about 20 feet/6meters tall. Once the spike reaches its full height, it seems to take a pause for a few weeks, not growing much taller, but concentrating on fully developing the buds and the paniculate branchlets they are perched upon.

By early June, the first flowers are open. In this species they are a bright yellow color and open first at the base, eventually reaching the terminal bunch at the tip a few weeks later. Individual florets don’t stay open for much more than a few days. A wide variety of pollinators from numerous bee and wasp species, to beetles and flies, and birds such as doves, orioles, woodpeckers, and hummingbirds visit the flowers by daytime. (Some of the visiting birds like the woodpeckers are probably drawn to the insects rather than the flowers, but in scrambling around they often end up helping with pollination regardless.) Night shift pollinators include sphinx months, numerous smaller moth species, other beetles, and several species of nectivorous bats.

The last phase of the agave’s life cycle includes setting the seed pods and making sure those are matured before the leaves age, change color, and die. Agaves spend their entire allotment of energy on one massive, exhausting reproductive event, pumping all of their water, nutrients, sugars, and starches into the tall spike and flowers and seeds. Many agave leaves turn attractive shades of yellow, orange, red, or even purplish as they senesce, a process rather similar to that undergone by deciduous trees preparing for cold winter weather in temperate climates. Although obviously a maple or aspen tree in fall color is not dying, but merely going dormant, whereas the agave will not continue on. It’s rather like the spawning of salmon: A single reproductive event conducted only once in a lifetime. Only the seeds and any surviving pups will carry on the gene flow of the species, repeating the cycle 25 or 30 or 40 years from now.