Ode to the Joshua Tree

No other plant exemplifies the Mojave Desert quite like the Joshua tree. But until relatively recently, it was almost completely unappreciated.

A large Joshua tree in the western Mojave. Original picture

The Sonoran desert has the Saguaro. The Colorado desert has the Palm tree. And the Mojave, it has millions upon millions of Joshua trees.

The Mojave has so many of these lanky yuccas, in fact, that they are often cited as an indicator species for the entire biome. If you see Joshua trees, you are almost certainly in America’s hottest and lowest desert. Or else you are relatively close to it — Joshua trees have also made their home in the southern Great Basin, in the highlands of Cajon Pass, and in the western Sonoran, as far as 100 miles from the California border.

Today, Joshua trees seem to be among the most universally loved desert flora. Southern California’s most-visited national park bears their name, featuring over a million of the evergreens. Multiple towns are also named after the plant, either directly, as in the case of Joshua Tree or Yucca Valley, or indirectly, as in the case of Palmdale, which was given its misnomered name by German settlers who mistook the yucca for a palm. The western subspecies of the Joshua tree are even protected by state law, and destroying one without permission can cost offenders $4,100 — nearly twice the maximum penalty for killing a Saguaro in Arizona.

But it was only relatively recently that Joshua trees earned their high reputation.

In the late 19th and early 20th century, the plants were so disliked that insulting them was practically a cottage industry among western explorers. John C. Fremont, the famed explorer-turned-politician, called them “the most repulsive tree in the vegetable kingdom,” fiercely criticizing their “stiff and ungraceful form.” Some years later, the writer Francis M. Fultz declared “whenever I see the Joshua trees, I think how considerate they have been in choosing to make their home where few men have a desire to live.” The traveler J. Smeaton Chase took the anti-Joshua tree vitriol to a whole new level, writing:

“One can scarcely find a term of ugliness that is not apt for this plant. A misshapen pirate with belt boots hands and teeth stuck full of daggers is as near as I can come to a human analogy. The wood is a harsh, rasping fibre; knife blades long hard and keen fill the place of leaves; the flower is greenish white and ill smelling; and the fruit a cluster of nubbly pods, bitter and useless. A landscape filled with Joshua trees has a nightmare effect even in broad daylight: at the witching hour it can be almost infernal.”

Even among the native peoples of the desert, Joshua trees were hardly prized as outstandingly useful plants. Although the fruits and petals of the plant were readily consumed, and the fibers could be weaved into sandals, baskets, and used as a base for fur robes, the plant was far less useful than other desert species. For instance, the banana yucca, a close relative of the Joshua tree, has over 200 recorded uses, including everything from a core staple food, to a gynecological aid, to rope fiber.

Joshua tree in full bloom. Wikipedia Commons

And yet, the humble Joshua tree now brings millions of visitors to the desert, and can be seen as a point of pride on countless postcards, t-shirts, and bumper stickers.

Much like its more glamorous neighbor, the California Palm tree, the Joshua tree is not technically a tree, as it lacks the secondary growth required for growth rings. Unlike the palm, however, its fibers undergo a process known as “lignification” that makes them nearly indistinguishable from regular wood. The Joshua tree is the largest, longest-living, and among the most cold tolerant of the yucca genus, being able to withstand temperatures as low as 20 Fahrenheit with ease, and possibly as low as zero degrees.

They make their home in the high desert, with the densest populations all located above 2,000 feet. The highest elevation the plants have been recorded at is over 7,000 feet, at nearly the altitude of Santa Fe, New Mexico. Somewhat uniquely for a desert plant, Joshua trees require a winter chill in order to flower, and are commonly seen in snow-prone areas of the Mojave.

Joshua tree in winter. Original picture

But perhaps the most striking fact about Joshua trees is just how little can be said of the species as a whole.

Joshua trees typically grow to around 10 to 20 feet, but some have reached gargantuan heights of 70 feet or more. The tallest ever recorded was a whopping 80 feet. Many never even reach 8 feet. The lifespan is also wildly variable. The average seems to be around 150 years, but Joshua Tree National Park’s “Elmer” is estimated to be over 500 years old. The oldest ever recorded was over 1,000 years old, before it was finally cut down by a short-lived Joshua tree papermill in the early 20th century. Even its famous branches are notoriously unpredictable. The yuccas begin life as a single spiky trunk, but can end up sprouting 100s of branches extending in every direction. Others will grow like straight lamp posts through their entire lives.

Seeing a young Joshua tree, then, is much like witnessing the first game of a poker tournament. The plant may go on to win the jackpot and live to be a towering, multi-century old behemoth, or it may soon cease growth entirely, and walk away empty handed.

A young Joshua tree in the Inyo Mountains. Original picture

One thing that can be confidently asserted about Joshua trees is that they are divided between two subspecies — the western variety seen in Joshua Tree National Park, as well as Death Valley, and an eastern variety, clustered around the Mojave National Preserve through to Arizona. Western Joshua Trees, Yucca brevifolia brevifolia, tend to grow higher and feature larger leaves, while Eastern Joshua trees, Yucca brevifolia jaegeriana, tend to be clustered together and more closely resemble bushes.

This divide was originally theorized to be due to geological isolation, as the lowest section of Death Valley is exactly in between the two subspecies, but more recent research points to a far more interesting explanation. As a monocot, Joshua trees need to be physically pollinated by an insect in order to reproduce, and this delicate dance is performed virtually single handedly by one species of moth. And just like the Joshua tree itself, the yucca moth is also divided into an eastern and western subspecies. A recent paper argues that each subspecies of moth is adapted to laying its eggs in only its respective Joshua Tree subspecies, so that the two types of tree may live virtually side-by-side and not cross-pollinate.

Joshua trees are what’s known as a keystone species. They form the foundations for their ecosystem, and are used by countless other species, from small plants that require their shade, to rodents and insects, and a reported 30 species of birds that form nests in their jagged branches. Some birds, such as the loggerhead shrike, are even known to impale their prey on Joshua tree leaves, in order to save the food for a later date, or simply to make biting off pieces easier.

It is also very clear that Joshua trees are placed at serious risk by climate change. As a high desert species, they require a unique blend of hot, dry summers, cold, snowy winters, and just the right amount of rainfall. Disrupt any part of that delicate balancing act, and their numbers begin to plummet.

In an oft-cited study, Joshua trees were found to be at risk of almost completely disappearing from Joshua Tree National Park, which is already located on the southern edge of their habitable zone. As this part of the desert has gotten precipitously hotter and drier in recent decades, the number of new Joshua trees has likewise plummeted. It is estimated that by 2100, over 90% of their range in the park will vanish, and the survivors will be confined to only the tallest peaks.

The eastern Joshua trees have seemed to fare even worse in a warming climate. 2020 saw a historically destructive fire break out in the Mojave National Preserve that set alight the densest Joshua tree forest on the planet. All told, 1.33 million trees burned, or the equivalent of the entire Joshua Tree National Park population. Scarcely three years later, in 2023, another fire came roaring through the eastern Mojave, this time killing another million trees. Unlike the Sierra Nevadas or coastal chaparral brushlands, the Mojave has not historically been a fire-prone area, and as a result, the species there have virtually no protection against the blaze. It is likely that the vast majority of trees burned will never recover.

2023 York Fire. Wikipedia Commons

One more Joshua tree question merits attention.

What’s with the name?

There is a common myth that Joshua trees were first named after Mormon settlers who saw the spiny yuccas “point” towards the west with their tentacle-like appendages, much like the biblical Joshua led the Israelites to the promised land. This claim, however, has not been substantiated by much historical data. Another explanation likens the Joshua Tree’s razor-sharp leaves to the swords of Joshua’s army. Still others claim the Joshua tree mimics arms outstretched in prayer or praise.

It seems fitting that there is so little agreement even on the origin of the Joshua tree’s name. The Joshua tree is, and always has been, a desert enigma. As Randell Henderson, the founder of Desert Magazine put it, “The Joshua tree… is a clown, a villain, an elusive fairy, a grandfather, a witch — in fact it is everything and anything you wish to make of it.”

Joshua tree forest. Original picture