Devilish weed provokes a call to arms ... and hands and trowels


I was watering oak saplings at the Sweet Springs Nature Preserve in Los Osos last fall when John Chesnut, the professional botanist on the crew, waved a few of us over.

“I’m no alarmist,” he said, “but of the bad guys, this is the worst of the worst.”

He was holding what looked like a young mustard plant — the sort that covers the county’s highways and fields with bright yellow blooms every spring. This seedling, he explained, was its desert relative: Sahara mustard. And it spreads like the dickens.

I just shrugged. Our small band of volunteers had already outwitted burclover, oxalis, even veldt grass — what did we have to fear from this spindly newcomer?

But over the next few days, I spotted that little weed around town, again and again. Construction projects are notorious for spreading alien seeds, and the digging up of practically every street in Los Osos for the sewer installation a year ago had engendered a huge crop of Sahara mustard. As fall turned to winter, those seedlings bulked up like they were mainlining steroids.

On the roadsides, mustard smothered the few California poppies struggling for life without rain. Along one stretch of South Bay Boulevard, it practically formed a hedge.

Alarmed, I googled the plant. Adapted to dry areas in North Africa and southern Europe, Sahara mustard is one tough customer. What we call drought, it calls happy. But floodwaters don’t phase it, either; a gel-like coating on its seeds protects them from both drying out and rotting, and they’re sticky, easily hitching a ride on animals or vehicles.

Sahara mustard likes sand but will grow just as riotously in gravelly soil and on rocky hillsides. It self-pollinates, so just one plant can produce 9,000 seeds. And skip the poison: by the time you’re likely to notice the weed, it’s too late for herbicides.

More troublingly, there are no useful biological controls, because the species (Brassica tournefortii) is closely related to important food crops like cauliflower, Brussels sprouts, and kale. In parts of Arizona, once-dazzling fields of wildflowers now look like Sahara mustard plantations; in Joshua Tree National Park, officials are bracing for “irreversible damage.” Localities in Southern California have doled out millions of dollars trying to eradicate the menace. And the mustard is winning.

When I looked up from my computer screen, I noticed that the yard of a recently sold house across the street was thickly rimmed with Sahara mustard; the new owners hadn’t moved in yet.

It resisted me as I tugged, as if the other end were gripped by the devil himself.

It started as a friendly gesture, an early welcome. But the next morning, when I switched from trimming the lavender in my garden to yanking Sahara mustard from my new neighbors’ yard, technically I was trespassing. And when I thrust those plants into my green waste wheeler, I was stealing.

I got to know the noxious weed very well that day. Its rosette of rough, hairy leaves lies flat on the ground, sometimes to a couple of feet in diameter. The leaves get smaller as they move up the stem, which can stay as short as 4 inches or catapult to 40; the flower is tiny, pale yellow, composed of four symmetrical petals.

At 9,000 seeds a pop, I figured, surveying my handiwork, I’d just saved Los Osos from about a quarter million mustard plants, and I felt pretty darn satisfied.

A few days later, however, while my husband and I were hiking in Arroyo Grande, I ID’d the species alongside a trail — which meant that the weed had also been dispersed via other agents, not just the sewer project. I’ve since learned that it’s been found in Morro Bay, Pismo Beach, the Oceano Dunes, Paso Robles and Santa Maria.

Last spring, The Los Angeles Times had bad news for anyone who’d been meaning to get to Anza-Borrego State Park for the amazing spring wildflower display: It was gone. The mustard killed nearly all the desert flowers.

So when a wall of Sahara mustard started rising on a tract of vacant lots near my home, I rattled my green wheeler over. For hours, Saturday after Saturday, I hoed and shoveled and lunged after roots, a one-person chain gang under the hot sun. I never did learn to get out there before the Santa Lucia winds’ 11 a.m. heat spike, but I refused to retreat, having sentenced myself to eradicating the plants before they could make seeds.

Unearthing a large plant’s thick taproot, I’d be hit with its distinctive cabbagey odor. Smaller plants, however, sometimes had an exceedingly long white root as fine and stretchy as a human hair. It resisted me as I tugged, as if the other end were gripped by the devil himself.

Once the mustard began to set seeds — which tends to occur between February and April — my guerrilla weeding languished. I figured there’d be no point in ripping out a plant if it had already cast forth its spawn.

And then the paradigm shifted again.

One afternoon as I was jogging home from the track at the middle school, a stiff breeze sent a pair of tumbleweeds as big as beach balls barreling toward me. When a Sahara mustard plant matures, it relinquishes its leaves but holds on to its seed capsules. The skeleton plant detaches itself from the ground and races with the wind, spewing seeds for miles.

My heart leapt into my throat. Those mustard tumbleweeds were heading straight for the Los Osos Greenbelt, that band of coastal scrub so many people worked so hard to preserve, where so much wildlife thrives.

I turned and sprinted after the tumbleweeds, grabbed one in each fist, and jammed them into a trash wheeler someone had left at the curb, my hands shaking. There’s something creepy about a plant traveling around on its own — like when a horror-movie lab experiment turns out to be sentient. Now, I realized, not only the greenbelt but even the Carrizo Plain are vulnerable. And when the wind blows from the east, those seed-strewing ghost plants can colonize Montana de Oro’s acres of fragile sand dunes.

That wasn’t the first time I availed myself of someone’s curbside cans. What, I wonder, did the homeowner who put out his eucalyptus branches and lawn clippings for collection on a Tuesday morning think when he returned home that evening to find instead a few burly clumps of Sahara mustard?

In this way, I’d been steadily adding to my potential rap sheet. Along with trespassing and stealing, I could now be nabbed for several counts of theft of services.

Merciful summer came and allowed me to go straight: Mustard is a winter annual, so it disappears in the warm season. I’ve been clean for months. But I’m starting to backslide.

In California, Sahara mustard has no natural pathogens or predators, so it easily outcompetes native plants. These native plants nourish the butterflies and quail, the rabbits and deer — and, in turn, the lizards and owls and fish and foxes and bobcats — that give our wild places their wildness. Without our native flora, we’ll lose our native fauna. And then, notes Eric Wier, chairman of Morro Coast Audubon Society’s lands program, people, too, will forfeit something invaluable.

You can’t combat Sahara mustard by weed-whacking or mowing; it will simply set its seeds from a shorter plant. In fact, notes John Sayers, an environmental scientist with California State Parks, “The folly of mowing is that you think you’ve gotten rid of the plants, but in fact the tenacious seeds have merely been dispersed.”

Even uprooted plants can manage to produce and scatter seeds, so the next year you’ll have an exponentially bigger crop. And don’t assume that this is something the county can simply handle: Marc Lea, deputy agricultural commissioner with the county’s Department of Agriculture, remarks, “If Sahara mustard gets a foothold the way veldt grass has, widespread control will simply be impractical. Once it’s well established, it becomes a long-term challenge that has to be dealt with for years and years to come.”

You want to yank the plant out by the roots. Don’t worry if you tear out some black mustard along with the Sahara — that one’s a nonnative, too, though not nearly as aggressive. (The chief differences: Sahara mustard’s smaller, paler flowers and rougher, bristly stems and leaves.) Use gloves, and try to remove the whole root. And most of all: act now, before it starts reproducing. Crush the seed production and you’ve hit the species where it hurts.

I slipped through last winter without being apprehended. But recently, I winkled out my first Sahara mustard seedlings at Sweet Springs, and when the cabbagey odor hit my nostrils, I again felt the call to arms.

I already know what will happen: I’ll see the weed near curbsides or in untended lots, and I’ll revert to my scofflaw ways. A lawyer friend tells me that when I removed a mustard plant from state park land, I committed a misdemeanor, punishable by up to 90 days in jail. So add that offense to trespassing and theft of services.

And therein lies an irony: Should I be prosecuted for my crimes on behalf of nature, I could wind up in an orange jumpsuit on a roadside crew, sentenced to pulling out rampant swaths of — what else? — Sahara mustard.

Bonnie Thompson lives in Los Osos. She is a volunteer with the Sweet Springs Nature Preserve and a freelance book editor.