The Mojave Desert’s iconic Joshua trees are blooming like crazy and, although theories abound, there is little consensus about why it’s happening.
From Joshua Tree National Park and into Nevada and Arizona, millions of the trees bear foot-long conical bundles of tightly packed, greenish-white flowers at the ends of their spiky branches.
What’s remarkable this year, experts say, is that just about every tree has bloomed or is flowering now, with fragrant bundles at the tips of just about every branch. Biologists and others said they can’t recall a year when the Joshua trees had more abundant flowers. Typically not all plants bloom, and those that do produce far fewer flower heads.
At Cima Dome, an area southeast of Baker that has the largest concentration of Joshua trees anywhere, the trees are resplendent.
“This is a once-in-a-lifetime phenomenon,” said Cameron Barrows, a UC Riverside researched ecologist who studies the species.
So why this spring? Speculation abounds.
One theory is that a series of late-summer thunderstorms in the desert last year gave the plants a vital infusion of water. Another is that the trees are responding to cool winters.
James Cornett, a desert biologist, rejected those theories.
He believes the trees are in a flowering frenzy to produce more seeds, giving the species a better chance of survival in a time of stress.
“Stress can be an inducement for reproduction,” Cornett said. “If it appears that they may not survive, one of the best strategies is to go out with an explosion of reproduction.”
Joshua trees are under stress because of two consecutive years of drought, he said. More stress comes from the slowly warming planet, which increases the rate of water evaporation from each tree, Cornett said.
In the western United States, temperatures on average are about 2 to 3 degrees warmer than they were a century ago, he said.
For about 25 years, Cornett has tracked Joshua tree growth, mortality, germination and flower production at locations in California, Arizona, Nevada and Utah.
He said Joshua trees growing in places that received no late-summer rains have just as many blooms as those in spots that were hit by the storms. And other winters have been just as cool, he said. But flower and seed production is up more than 40 percent when compared with the previous best season in the 25 years of his study.
He added that he sees no coincidence in the equally spectacular blooms of yuccas in the Mojave. Joshua trees and yuccas are closely related.
David Lamfrom, the California desert manager the National Parks Conservation Association, visited the Mojave National Preserve on Saturday, April 6, to experience the unusual bloom in one of the densest Joshua tree forests in the entire Mojave.
He pointed out the pink hue the blossoms picked up as the sun set, and he noted the sweet, coconut-like fragrance that floated among the trees. Insects attracted by the nectar in the flowers buzzed from plant to plant.
The blooms now are like pale flames sweeping across the northern Mojave, starting east of Baker and extending east to the Colorado River and beyond, Lamfrom said.
Biologists he has spoken with attributed the phenomenon to the rains last year and the cool temperatures that followed, he said.
Regardless of the cause, the bloom of 2013 will give Mojave ecosystems a nutritional shot in the arm. Energy stored in the trees becomes edible nectar, fruits and seeds. Insects gorge on the nectar. Birds and lizards eat the insects. Rodents dine on the seeds and fruit. And coyotes and other predators will eat the rodents.
The bloom is expected to last for the next few weeks, although trees already are producing seed pods in some areas.
At Joshua Trees National Park, the flowering is still heavy in the Hidden Valley area, along the road to the Keys View lookout point, near Barker Dam and along the Pine City trail. The trees at west side of the park have gone to seed.
In the Mojave National Preserve, the Cima Dome area off Cima Road south of Interstate 15 is in full bloom. Lamfrom said Cima Dome has the largest Joshua tree forest in the world — well worth the detour for people driving to or from the Las Vegas area.