Agave utahensis clonal rings: guest post by Dan Zarrella

In September 2024, Dan Zarrella contributed an engaging guest post on Agave utahensis in habitat and in cultivation (see here). Dan is back with a fascinating article on Agave utahensis clonal rings as artifacts of resource management by the Southern Paiute people of southern Nevada.

Dan Zarrella lives in the Las Vegas area and has spent years exploring the Mojave Desert. His YouTube channel contains 75+ videos on Agave utahensis. In addition, he shares his field observations and his experience growing Agave utahensis on his website Mojave.lv. He also sells choice seed-grown Agave utahensis through Mojave.lv to support Project Eborispina, a long-term effort to survey and document eborispina populations in southern Nevada. To learn more about Project Eborispina, watch this video.

Partially hollow Agave utahensis clonal ring in the snow

Are Agave utahensis clonal rings living artifacts?

by Dan Zarrella, Mojave.lv

In Mexico, many of the species of agave that are used for mescal and tequila are under threat, both by extinction and the loss of genetic diversity due to over-harvesting. But modern populations of Agave utahensis in Southern Nevada—particularly nevadensis near archeological sites that show evidence of indigenous harvesting and roasting—appear robust and healthy, with high levels of variation. I conducted a study of these indigenous resource management practices and Agave utahensis populations to start to understand what we can learn from them, and I’m super excited to share that I’ve published the results of that study in the Winter 2024 issue of the Cactus and Succulent Journal published by the Cactus and Succulent Society of America (CSSA). That paper is 17 pages long with 52 different sources cited. In this blog post, I’m going to cover the highlights of that article, but if you want to nerd out about the details, definitely go check out the full paper, either in Cactus and Succulent Journal 96-4 343-359 (2024), or as a free PDF download from my website.

Agave utahensis reproduction

As many readers probably know, Agave utahensis, like most species of Agave, is monocarpic, meaning it flowers once in its life and then dies. During this single flowering season, it grows a ten to fifteen foot tall flower stalk (often growing as fast as six inches a day), and the rosette at the base of that stalk turns yellow and dries. Over the course of the next few years, that rosette decomposes and eventually completely disappears into the desert floor. The other method by which Agave utahensis reproduces is via clone production; the species readily produces rhizomal offsets around its base. It is rare to see a solitary mature utahensis in habitat—the vast majority of plants occur in clumps. As the oldest plants in these clumps flower, die, and dry up, these clumps turn into hollow rings, sometimes called “fairy rings.”

Agave utahensis var. nevadensis flowering in early May

Indigenous use of Agave utahensis

Ethnographic reports of Southern Paiute oral tradition recorded several rules and protocols around the harvesting of Agave utahensis that functioned as effective resource management. While there was no ownership of agave stands, the harvesting and roasting process was overseen by a single specialist, who ensured that only mature agaves were harvested using the correct technique, and that areas were not over-harvested. When the first Europeans began to visit Southern Nevada in the late 1700s, they reported finding tens of thousands of Southern Paiute living in the region. Interviews with indigenous consultants remarked that during agave harvesting season, so many people were involved in collecting plants that the fires of their camps on the hillsides could be seen from the valleys. The United States government assumed control of the area in 1848, and Mormon settlement began in 1850. By 1880, Southern Paiute populations had been reduced by 90% and their traditional way of life (including agave roasting) was effectively over. This means that populations of Agave utahensis were subjected to at least 700 years of large-scale harvesting by the most recent indigenous residents of the area, and at least 7,000 years of use by other groups.

Throughout its life, Agave utahensis stores energy in its rosette in the form of fructans, a form of carbohydrates that is indigestible to humans. When flowering begins, the plant converts all those stored fructans into simple sugars to power the fast growth of that giant flower stalk and produce the copious amounts of nectar needed to attract pollinators. Those simple sugars are digestible (and delicious) to humans, but once the flower stalk is at full height, they’re all used up. Therefore, an Agave utahensis is “ripe” only when it’s just begun to flower, when the stalk is hip-height or shorter. This is when the Southern Paiute harvested them. Waiting until flowering has begun before harvesting a plant also ensures that plant has had as long as possible to reproduce via offsets.

Across indigenous groups, ethnographic recording of oral tradition also shows consistent methods for the actual harvesting of Agave utahensis rosettes. A sharpened stick was used to pry the heart of the plant away from its roots and offsets. Several sources I reference in my article specifically highlight the practice of leaving roots and offsets in place, ensuring productive future harvests. This method is quite similar to the modern method of agave propagation called “coring” in which the apical meristem at the center of the rosette is damaged. This damage induces the plant to produce more offsets than it would have otherwise—it’s possible the indigenous harvesting technique also had this effect.

A ring of Agave utahensis clones. By the time flowering occurs, most plants have produced several offsets, and often there is more than one generation in a clonal ring. As flowering plants die, decay, and disappear, the clump develops a hollow center, forming a “fairy ring.”

My research

For this paper, I conducted a field survey of 96 different Agave utahensis clonal rings at three different sites, all near roasting pits. I measured and photographed these rings and created a dating methodology designed to estimate their age. I detail this methodology in the article; basically, it uses two number ranges to transform clump size to estimated age: age at flowering (10 to 20 years) and rosette size (4 to 5 inches) at flowering.

Agave utahensis clonal ring shapes

I identified solid clubs, partially hollow rings, hollow rings, open (U-shaped) rings, and broken rings.

Solid clumps

Before flowering, individual plants grow rhizomal offsets in a ring around their base, and some of these offsets may themselves begin to grow their own offsets before the oldest individual flowers. This results in a solid clump shape. In my study, rings of this shape had the youngest average estimated age.

Solid clump

Hollow and partially hollow rings

When the oldest plants in these solid clumps flower, die, dry up and begin to decompose, the clumps begin to form partially and then completely hollow centers. Partially hollow rings in my survey had the second youngest average estimated age, followed by hollow rings.

Partially hollow ring

Hollow ring

Open rings

Eventually, most hollow rings seem to break open into a U shape. These openings mostly occur at the side of the ring facing up the slope the plants are growing on. This pattern has been noted in other species of clonal plants; I detail this and potential reasons in my article. In my survey, open, U-shaped rings had the second oldest average estimated age.

U-shaped ring

Broken rings

As an open ring continues to age, it begins to break apart and individual sections begin to grow offsets in solid rings again, forming what I’m calling broken rings. These are the hardest shapes to visually identify in the wild, simply because it’s tricky to identify them all as belonging to a single colony. The broken rings I surveyed had the oldest average estimated age, but I likely missed the oldest of this shape because of that difficulty.

Broken ring

Ring ages

Using mid-range values of these two numbers, the largest clonal ring I surveyed had an estimated age of at least 160 years, meaning it existed during the period of large scale harvesting by the Southern Paiute. Using high range values, 13 clonal rings dated to this time period. This means that it is very likely that many of the Agave utahensis clonal rings in habitat today are living artifacts of indigenous resource management. Their healthy and diverse populations bear evidence of the conservation protocols of the First Peoples communities that used them for thousands of years. Three of the most important of these protocols are centralized oversight, harvesting technique, and timing.

Further research

There are many areas where further research holds the potential to uncover valuable information, particularly with regard to conservation practices, and what we can learn from indigenous resource management and apply to modern agave harvesting.

Text and photos in this post © 2024 by Dan Zarrella. All rights reserved.

© Gerhard Bock, 2024. All rights reserved. To receive all new posts by email, please subscribe here.