JOSHUA TREE, Calif. —

Many a music lover in the Pacific Northwest may never have been closer to a Joshua tree than the cover of a rock album.

When the Irish band U2 released its acclaimed collection, “The Joshua Tree," in 1987, the sleeve art featured a photo of lead singer Bono and his band mates beside an odd, yucca-like tree in California's remote Mojave Desert.

Although that particular photograph was taken in an area west of Death Valley, an entire national park in Southern California is devoted to preservation of this unique plant, which was named by devout Mormon pioneers who were reminded of the prophet Joshua raising his arms to the heavens in prayer.

Occupying more than 1,200 square miles (an area greater than the state of Rhode Island) northeast of Palm Springs, and immediately south of the sprawling Twentynine Palms Marine Corps base, the park is known for its remarkable desert flora and fauna, as well as a stunning geology that draws rock climbers from far and wide.

Enveloping a transitional zone where the higher Mojave descends to meet the lower Colorado Desert, and ranging in elevation from more than 5,800 feet down to nearly 500, the park was established as a national monument in 1936. It was upgraded to national park status in 1994, 10 years after it had been designated by the United Nations as a world biosphere reserve.

It is a worthy detour of a day or more for anyone traveling between Las Vegas and Los Angeles, as photographer Barb Gonzalez and I did last month.

A curious plant

Rangers estimate the number of Joshua trees in the park to be about 5.5 million. They grow mainly in widely spaced “forests" above 2,000 feet, in the northwestern section of the park, where winter snowmelt helps provide the 6 to 8 inches of annual precipitation they need to grow.

The Joshua tree is a curious plant. In the traditional sense, it's not a tree at all, but a “short-leaf yucca" according to its Latin name, Yucca brevifolia. It has no growth rings; instead, its trunk is made up of thousands of small fibers that grow at a rate of 2 to 3 inches a year, according to park naturalist Darwin Spearing. Some may appear fragile, but plants such as the giant Joshua tree that stands today in the park's Queen Valley — 42 feet tall, a dozen feet around — may be centuries old.

Pollinated only by the nocturnal yucca moth, according to Spearing, the Joshua tree produces large clusters of beautiful white flowers in early spring. Our visit was a couple of months too early for this spectacle; instead, we observed the evergreens' clusters of serrated, bayonet-like leaves, arranged in dense spirals off individual branches.

Seen against a backdrop of giant boulders stacked like marbles, framed by a sky that was almost impossibly blue and distant peaks fringed with snow, they created a remarkable panorama.

Park access

We stayed three nights in Cathedral City, just outside of Palm Springs, a 90-mile drive east of downtown Los Angeles and 280 miles southwest of Las Vegas. We used the Red Lion Inn & Suites as our base for exploring Joshua Tree National Park — from morning to dusk — as well as the palm oases of Indian Canyons on the nearby Agua Caliente Indian Reservation on the following day.

The drive from Palm Springs area to the village of Joshua Tree, near the West Entrance Station to the national park, takes about 45 minutes. The Twentynine Palms Highway (California state Route 62) climbs more than 3,000 feet in 35 miles into the Little San Bernardino Mountains. It crosses the easily visible San Andreas Fault to Yucca Valley and, a little farther, the Joshua Tree Visitor Center.

From here, there are two primary routes through the park. Park Boulevard follows a winding, 38-mile loop through the high Mojave Desert country between Joshua Tree and the Mara Oasis Visitor Center at Twentynine Palms, with side roads to such attractions as Keys View and the Barker Dam. Pinto Basin Road runs 46 miles to the park's south entrance, off Interstate 10 near Cottonwood Spring, from a junction with Park Boulevard 8 miles south of Twentynine Palms.

So impressed were we with the upper desert, we wound up staying until we saw the sun setting with a brilliant pinkish glow. We saved Pinto Basin — said to be spectacular during the spring wildflower season — for another time, leaving until then a garden of cholla cactus, a patch of spindly ocotillo and the Cottonwood Spring oasis, where the park has a third visitor center that focuses on Colorado Desert attractions, for a future visit.

Beep beep!

If there was one highlight of our visit, it came at a turnout near Hidden Valley, a cloistered alcove between huge boulders where cattle rustlers of the late 19th century are rumored to have hidden their stolen livestock.

A short time earlier, we had seen a wily coyote cross the road in front of us. “In pursuit of the roadrunner, no doubt," I quipped, thinking of the Looney Tunes cartoon characters. But I had never seen a roadrunner, native to the southwestern United States and Mexico, in the wild.

As luck would have it, the long-legged bird was just waiting for his cue to enter the scene.

While Gonzalez set up her tripod to photograph a desert landscape, I sat behind the wheel of our car, surveying the magnificent scenery that spread before me. A movement at ground level distracted me. I glanced downward, and there, staring up at me, was a roadrunner.

It almost seemed to be begging for a handout, although I knew that the roadrunner's preferred diet is insects and lizards, neither of which I had in my lunch bag.

I stuttered in an attempt to alert Gonzalez without startling the bird, which, though capable of flight, can run 20 miles per hour or faster. She succeeded in getting a couple of good shots before the roadrunner, discovering that no food was forthcoming, skittered off into the brush-covered desert.

Despite its desolate appearance, the Mojave is as rich with animal inhabitants as it is in plant life. Bighorn sheep study the desert floor from rocky heights. Desert tortoises march at their own slow, steady pace across the remote landscape. Jackrabbits, ground squirrels and wood rats find shelter in burrows. A plethora of reptiles, from nocturnal lizards to venomous rattlesnakes, hide in the rocks. And everywhere are birds: hawks, owls, woodpeckers, songbirds, quail and the ubiquitous ravens.

The foliage is not restricted to Joshua trees. Far from it. While these strange, ancient yuccas are the park's namesake, they share the park with many other species. Scrub oak, juniper and piñon pine are prevalent in the Queen Valley and around Barker Dam, a small, rain-fed reservoir near the Keys Ranch homestead. Creosote and blackbrush are common in the arid landscape.

And there are cacti — not in the numbers they are found in some Arizona deserts, perhaps, but certainly well represented. In particular, we saw prickly pear, with pads like beavers' tails; ocotillo, gangly and spider-like; silver cholla, sun glinting off its glistening pointers; and pencil cholla, its long spikes issuing a “stay away" warning.

Other highlights

Park rangers lead a walking tour (by reservation) of Bill and Frances Keys' Desert Queen Ranch, which operated from 1918 to 1963 as one of the only homesteads in this remote region. Nestled beneath towering outcroppings of granite known as the Wonderland of Rocks, 2.5 miles from the Hidden Valley campground, the ranch is a tribute to the perseverance and tenacity of a “desert rat" couple who found a way to live in this foreboding location for 45 years.

Bill and Frances Keys did whatever it took to survive. As a cattle rancher, Bill Keys raised the height of the Barker Dam from 9 to 15 feet to water his livestock. He was a prospector and miner, a mill operator, a road builder. His wife was doctor and teacher to their four children, a gardener and housekeeper for the whole family.

Rangers also tell the story of Bill Keys' imprisonment. In 1943, they say, he turned the tables on a feuding neighbor, shooting and killing the man in self-defense. He was sentenced to 10 years for manslaughter, but served only half of that time when writer Erle Stanley Gardner, the creator of “Perry Mason," took up his case and helped win Keys' parole. He was later pardoned.

Unfortunately, our visit didn't coincide with the Keys Ranch tour schedule. But we did enjoy a 1¼-mile walk around Barker Dam, even though its reservoir was dry at the time of our visit last month. Built around 1900 for mining as well as livestock, its vegetated fringe makes it a popular place for wildlife spotting.

Our trail took us past a natural alcove that preserves a set of centuries-old Cahuilla Indian petroglyphs. They have been painted over by vandals who may have had good intentions, but whose action many decades ago permanently defaced the primitive art.

Five miles south of Hidden Valley, the paved road leads to a viewpoint that looks almost a mile down to Palm Springs and the Coachella Valley. From Keys View, elevation 5,185 feet, the vista stretches across the San Andreas Fault between Mount San Gorgonio, at 11,503 feet the highest summit in southern California, and the inland Salton Sea, 227 feet below sea level.

There are many places for rock lovers to clamber over the granite here. One of the most popular is Jumbo Rocks, toward the eastern end of Park Boulevard. Rock climbers — some technical, many others mere scramblers — love the maze of domes, towers, steeples, arches and balanced rocks. In fact, the entire park is a paradise for rock climbers. We even saw one young man practicing walking a tightrope between two blocks.

At a campground amphitheater near Jumbo Rocks, rangers give occasional evening lectures on geology. According to the official “Joshua Tree Guide" published by the National Park Service, the creation of these rock formations began more than 100 million years ago, when molten rock oozed upward through the earth beneath overlying rock, or gneiss. Vertical and horizontal fractures in the cooling process allowed ground water to percolate through; over time the gneiss was eroded and the angular blocks beneath settled into the apparent piles seen today.

Spring, from all accounts, is the best time to visit. Winter snowmelt has encouraged myriad wildflowers to blossom, and temperatures are comfortable: Typical daytime highs in April and May are in the 80s, with overnight lows in the 50s.

It was cold, I have read, when U2 did its desert photo shoot. It was chilly in January when I visited. As much as I look forward to a wildflower-season return, I'll pass on a mid-summer visit, when high temperatures here soar well above 100 degrees.