BORREGO SPRINGS, Calif. — Locals call it "The Miracle of March." If spring rains and temperatures are just right, the forbidding mountains and parched badlands here are transformed into dazzling panoramas of wildflowers that draw thousands of tourists.
The crowds provide a major boost to Borrego Springs, a community of about 3,500 permanent residents in the heart of 640,000-acre Anza-Borrego Desert State Park. When blossoms abound — every five to seven years or so — visitors spend freely on gasoline, groceries, souvenirs, sun hats and cold drinks as they seek directions to "flower hot spots."
Now, a botanical invader is threatening the economic and environmental lifeblood of this northeastern San Diego County community. It is Sahara mustard, a rapidly spreading nonnative menace that is robbing wildflowers and low-lying cacti of water and sunlight with its carrot-like taproots and large leaves.
The invasion has prompted Borrego Springs to downplay its image as a quaint town surrounded by seas of wildflowers rippling in the desert breeze. A new advertising campaign promotes a mecca for golf, art galleries, bird watching, hiking, cycling, star gazing, photography and, in certain intensively weeded patches, enjoying wildflowers.
"We love wildflowers because they are beautiful and part of the landscape we cherish — but they do not define us," said Linda Haddock, executive director of the Borrego Springs Chamber of Commerce. "The mustard is forcing us to change to course. We're repositioning ourselves and diversifying our base."
For the first time in memory, the Borrego Springs Village Guide, a free brochure handed out to visitors, does not feature images of wildflowers on its cover. Instead, the 2013 edition touts a huge metal sculpture of a dragon, part of a menagerie of life-size creatures created by artist Ricardo Breceda.
Next year's guide will promote another local treasure: dark night skies. With the nearest traffic light about 50 miles away, Borrego Springs is a certified International Dark Sky Community, one of only four in the world.
"We're learning to compete with the mustard," said Fred Lee, a Borrego Springs resident and former Anza-Borrego Desert State Park ranger. "If we don't adjust, we'll dry up and blow away.
"The important thing is this: There are many, many wonderful things to do and see in Borrego Springs," he added.
That message is raising the profile of natural rarities that had been largely overlooked for years.
On a recent weekday morning, a dozen naturalists gathered on a small hill along Digiorgio Road at sunrise to witness hundreds of migrating Swainson's hawks spiraling over trees they had roosted in overnight.
The locale, once best known for its wildflowers, is believed to be one of the most populous sites for the species in North America. The annual "tornadoes of hawks" draw wildlife enthusiasts from across the nation.
Sahara mustard made its way to the American Southwest with imported date palms in the 1920s. Since then, it has spread from Central California to Texas and from Colorado to Mexico.
The plants first showed up here a decade ago and quickly infested the landscape, their numbers rising exponentially. To the casual observer, there are few signs of the battle against Sahara mustard.
But in a tourist destination where occasionally robust blooms attract hundreds of thousands of visitors during March and April, "local merchants are hurting," said Chuck Bennett, executive director of the Anza-Borrego Foundation. "We don't get too many visitors in summertime. They don't like the 110-degree temperatures."
Coalitions of business leaders, property owners and research scientists are trying to control the weed. Eradication campaigns led by hired crews and volunteers have created 2,000 acres of "mustard-free zones" in California's largest state park to ensure that tourists have wildflowers to admire.
But efforts to eliminate the mustard have been unsuccessful.
"It's everywhere," David Garmon, a part-time resident of Borrego Springs, lamented as he strode through once-pristine Tubb Canyon on the western edge of town. "Just look at the way it's germinating in and around stands of sand verbena, paintbrush and even barrel cactus."
Kneeling for a closer look at hundreds of mustard plants overwhelming a knee-high cholla, the president of a newly formed anti-mustard group called Tubb Canyon Desert Conservancy shook his head in dismay and added, "It's heartbreaking to lose this type of natural beauty."
The conservancy has partnered with UC Irvine's Steele/Burnand Anza-Borrego Desert Research Center, which is taking advantage of the region as a living laboratory.
"There is so much we don't know about this invasion and its impacts on local rhythms of life," said Travis Huxman, faculty director at the UCI center. "Are native species going to be lost forever? Can the mustard be stopped? Is global climate change a driving force in what is happening here?"
As he made his way through a stand of chollas, Huxman could not resist stopping to uproot an invader topped with small, dull yellow flowers.
Tossing the weed aside, he said: "The only annual you're likely to see out here this March is Sahara mustard."