Guide: Seven Incredibly Old Mojave Desert Plants
Editor's Note: Driving between Los Angeles and Las Vegas may summon up those middle-of-nowhere feelings. On the outset, the vast spaces of monotonous desert look empty, but take a closer look with the help of this guide and you'll be spotting plants that can or have lived thousands of years.
Chris Clarke, a California desert resident and advocate, earlier this month spoke at the California Native Plant Society's Conservation Conference about old-growth plants in the desert. He's also a regular KCET.org commentator and here shares what's easily overlooked.
The desert is a harsh place to live. Plants that grow here for more than a single growing season grow slowly, a few inches or less in a good year. And as is the case with the fabled bristlecone pine of California's White Mountains, which can live for 5,000 years or more, that slow growth habit can bring with it immense longevity. Many of the plants native to the Mojave Desert have astonishingly long lifespans. But not necessarily the plants you might guess.
It's easy to find references to "ancient Joshua trees," for instance, and people will tell you of trees with ages upwards of 700 years. The trees can certainly look ancient; gnarled and twisted and battered. But as it turns out, that's not the case. It's hard to determine Joshua trees' ages precisely, as their trunks lack annual rings, but based on the rate at which the trees grow, it looks like most die before their 200th birthday, with almost none reaching 300. That's impressive enough compared to our measly threescore years and ten, but it's not bristlecone-caliber ancient.
The Joshua tree's cousin the Mojave yucca (Yucca schidigera) is a different matter. Sometimes mistaken for a Joshua tree despite its coarser build and the fact that it rarely branches, a Mojave yucca can outlive its more graceful relative by many centuries. An individual Mojave yucca plant grown from a seed will, when it reaches maturity after a century or so, grow little side shoots that eventually become full-fledged adults themselves. Those side shoots have their own side-shoots, and so does the next generation, and the next. Eventually the original shoot will die out and decay, leaving a ring of yucca stems that are, unless their subterranean connection is severed, essentially all the same plant.
We can estimate the age of a group of these clonal shoots by measuring its width and calculating how long it would have taken to reach that width. Estimates of growth rate for Mojave yucca clumps vary by about a factor of three – a foot wider each 30 years, or each 100? – but even using the more conservative 30 year rule of thumb, Mojave yucca clumps in excess of 700 years abound throughout the Mojave Desert. One ring near Lucerne Valley was described in the New Scientist as in excess of 12,000 years of age, quite possibly an overexuberant estimate. That particular ring is certainly several thousand years old, however.
That's not to say there aren't 12,000-year-old plants in the Mojave, though. Take the creosote bush, Larrea tridentata, which possesses the same habit of forming clonal rings that expand, very slowly, over the millennia. The best-known of these creosote rings is "King Clone," near Landers, dated by biologist Frank Vasek at about 11,700 years of age. When the creosote seed from which King Clone grew hit the soil, it might have been tamped down by a mammoth or a Shasta ground sloth.
King Clone is unbelievably old, but there are plenty of creosote bushes in the Mojave that are merely astonishingly old. One specimen in a Lancaster city park has been estimated at about 800 years old. It's a nice looking plant, large and rather impressive - and there are many thousands of creosote bushes just like it throughout the Mojave.
Big Galleta Grass
Even the lowly bunchgrasses in the Mojave can attain significant age. In a rephotography study of 19th century photographs from the Grand Canyon area, one of the plant species found to have persisted for more than a century was the unprepossessing native bunchgrass big galleta (Pleuraphis rigida). A lifespan in excess of 100 years isn't bad for a grass.
Big galleta is easily recognizable: it grows throughout the Mojave (and elsewhere in the California Deserts) in washes, on broad plains, in clefts in rocks, and just about anywhere else it can get a toehold. In good conditions, like those shown here in the Colorado Desert west of El Centro, a galleta clump will get to be about three feet tall and as wide. It's a favored browse plant for many animals including bighorn sheep and desert tortoise, and it serves as a nurse plant for hundreds of other desert plant species, providing shelter and camouflage as tender seedlings slowly harden to the rigors of the desert.
Among the plants that take advantage of galleta's nursery are chollas, those fiercely armed jointed cacti with the intimidating spines. At first glance, chollas would seem like excellent candidates for serious longevity, and many of them do in fact live for centuries. The rather nondescript buckhorn cholla, Cylindropuntia acanthocarpa, may well outlive most of its kin.
Ranging from the easternmost reaches of the California Mojave through Nevada, Utah, and Arizona into northern Mexico, buckhorn cholla differs from many other chollas by its moderately sparse coat of spines, and the unique purple-red color of its floral filaments, a nice contrast with its (usually) yellow flowers. When it's happy a buckhorn cholla can reach 10 feet tall, but three is more usual.
To my knowledge no one has nailed down a reliable figure for buckhorn cholla longevity, but an article published in 2000 offers an intriguing hint that that longevity may be very long indeed. In a 15-year survey of a plot of land in the Sweeney Granite Mountains Desert Research Center in the Mojave National Preserve, Martin Cody and his colleagues charted the "births" and deaths of shrubs on that plot from 1981-1996, and extrapolated the likely maximum lifespans of many of the species growing there. Some species turned out to have impressive potential lifespans indeed: more than 700 years for east Mojave buckwheat, 425 for spiny Menodora, and a couple species with even longer lifespans. Four species had no casualties over the 15-year study period, and so the researchers could not establish a likely maximum lifespan. They were Mojave yucca, creosote bush, buckhorn cholla, and one other shrub we'll get to in a minute.
That study doesn't offer enough data to say conclusively that buckhorn cholla can live for millennia, but given the other species on the "too long to measure" list it sure looks promising. It may well be that that pesky buckhorn cholla stem that has painfully attached itself to your pant leg sprouted some time around the Battle of Hastings.
This odd little plant, known botanically as Ephedra nevadensis, was the other "lived too long to measure its age" species in Martin Cody's study referenced just above. This seems fitting: Mormon tea is what people sometimes misleadingly refer to as a "living fossil" in that the vast majority of its close relatives have gone extinct. (One of its cousins that's still around, Welwitschia, is possibly the oddest long-lived desert plant ever, but it isn't native to the Mojave.) Ephedra is a gymnosperm, more closely related to pines and spruces than it is to true flowering plants. It's easily recognized by its oddly jointed, leafless stems bearing either small cones or the scars from former cones at the joints.
Mormon tea is so-called because it has been used as a beverage for both medicinal and recreational purposes: it contains moderate amounts of ephedrine and pseudoephedrine, enough for a mild stimulant (and decongestant) effect. (Don't try this yourself unless you are certain you've got the right plant. Some plants that should not be consumed resemble Ephedra enough to confuse people not well-versed in plant identification. And never take cuttings of any plant on protected or private land without permission.) Mormon tea is an important wildlife food source, with large animals browsing on the stems and smaller ones gathering its seeds. It isn't showy or prominent, unless you're looking for it: it just plugs along, feeding wild things and growing back after it's browsed.
Mormon tea provides a telling indication of just how little we know about even the most common desert plants. While Cody's study indicated that the species may have a very long lifespan, the US Forest Service describes the species' lifespan in frustratingly vague terms as "more than 100 years, many other reputable-seeming sources describe the plant as short-lived -- possibly describing its longevity in cultivation or under heavy grazing pressure. We know so little about this plant, and it's not exactly rare. The desert is truly terra incognita, and developing desert wildlands may destroy treasures we don't even know exist.
At first glance, this species -- Thamnosma montana -- could be mistaken for Mormon Tea by a beginner: its stem structure is roughly similar, and its leaves are few, small, and temporary. This underscores the importance of getting your plant IDs right before making tea: Turpentine broom has variously been used as an emetic, a laxative, a hallucinogen, and a pesticide.
Fortunately, it isn't really that hard to tell the two species apart. Thamnosma montana is a distinctive chartreuse color, and holds small, deep purple flowers up and down its stems. A member of the same plant family (Rutaceae) as citrus, it grows at middle elevations below about 5,500 feet. It's unpalatable to most livestock, though bighorn sheep do eat it. One of turpentine broom's chief ecological values is as a soil-builder: its dense crown of thin stems catches wind-blown organic matter and holds it.
The species is also an important host plant for butterflies. A few years ago on Cima Dome in the Mojave National Preserve, I watched as an unusual hatch of fall butterflies swarmed the desert. One of the species that showed up, the Indra swallowtail, was especially drawn to the abundant turpentine broom there on the Dome, and I watched as the females laid one tiny, jade-colored egg after another on the chartreuse stems, there to hatch out as caterpillars to eat the plant's meager leaves.
One other difference between turpentine broom and ephedra: nobody refers to turpentine broom as "short-lived." Cody's study put an approximate ceiling on the species' longevity in the Mojave Preserve, saying that about five percent of the individual turpentine broom plants under study would likely live around 1,150 years.
Alert readers will recall that Coleogyne ramossissima, a.k.a. the almost ubiquitous blackbrush, has already been featured here at KCET.org as part of an incredibly long-lived vegetative community. As that previous article explains, a solid cover of blackbrush, which you can find throughout the Mojave at elevations between 2,000 and 5,000 feet, may take as long as 15,000 years to develop, or even longer.
Individual blackbrush plants are no slouches in the longevity department, either. Cody's study in the Granite Mountains put blackbrush's top five percent longevity at around 1,250 years.
The list of potentially ancient plants in the Mojave goes on: these are merely some of the most common and easily seen species. You can see hundreds of individuals of every single one of these species on a drive from L.A. to Las Vegas without leaving the Interstate. Many of them are centuries old, or even millennia. All of them are worth learning more about, cherishing and protecting.