The desert is only lightly colored this month with the oranges, scarlets, pinks, yellows, and purples of wildflowers. Blame another season of little rain. For businesses in communities that depend this time of year on a problematic economy of wildflower tourism, March can be the cruelest month.
Wildflowers have their own reasons, blooming profusely in one spring out of five or six.
This year, California poppies are beginning to bloom on the hillsides of the San Jacinto Valley beyond Barstow and on the Santa Rosa Plateau above Murrieta. But other desert swales and dunes, which might have been brightly colored by now, are drifted with the lanky stalks and yellow blooms of an increasingly dominant non-native weed: the Sahara mustard (Brassica tournefortii).
The Arizona-Sonora Desert Museum reported in 2005 that three-quarters of the most famous wildflower areas in California and Arizona were already overrun.
"Weed" and "wildflower" are ambivalent terms in California, flowing into and out of popular appreciation, the habits of home gardeners, and the efforts of lifestyle marketers. Escaped geraniums grow as weeds in the empty lots of Los Angeles. They are (or were) hothouse plants in Boston.
The Sahara mustard is firmly (for now) on the "weed" side of the divide between tolerated and noxious plants. According to David Garmon, president of the Tubb Canyon Desert Conservancy in San Diego, the spread of Sahara mustard risks turning the canyon "into a mustard wasteland devoid of the biodiversity needed to sustain desert wildlife."
A recent Los Angeles Times story characterized the weed as both an economic and an ecological disaster.
Sahara mustard is hard to control. The most effective means is the least practical: hand weeding before the young plants go to seed. Volunteers are being recruited this month at Joshua Tree National Park to pull and hoe as part of a regional "Hold the Mustard" project coordinated by the Morongo Basin Conservation Association. (For information about the weed control program, email email@example.com.)
Sahara mustard is a relatively new arrival in Southern California. The plant is supposed to have hitchhiked here in the 1920s and spread through the outlying areas of San Diego, Imperial, and Riverside counties. The speed of substitution of wildflowers by Sahara mustard picked up in the 1980s, perhaps hastened by the spread of subdivisions into the desert fringe. The plant grows best in disturbed sandy soil and along road cuts.
The succession of one possessor of the land by the next is part of the mythology of California: Native Americans replaced by Spaniards, Mexicans replaced by Americans, Anglos replaced by immigrants, immigrants (it now seems) replaced by the native-born.
Some in those equations have looked on the others as invasive, as weedy, as tending to crowd out.
We found a place for wild oats (brought by the Spanish) and eucalyptus trees (brought by American entrepreneurs) and a thousand other non-native species. Like palms trees, some are fully part of our iconography. Sahara mustard doesn't look to be as conformable to our desires.
Sahara mustard may well be a permanent weed in our garden and another symbol of our broken paradise.
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