Thorns in the Side
Their blooms are impossibly vibrant. They dot hillsides and open fields in neon bursts of purple. They are as soft as powder puffs, perched atop 6-foot-tall stems that resemble giant celery stalks. Delicately, they wobble in the breeze.
But don’t be fooled.
These violet flowers are vicious ornaments for one of California’s nastiest, hardiest weeds: artichoke thistle. Besides sporting inch-long daggers that draw blood with ease, the spindly plant is infesting Orange County’s native grasslands like never before, invigorated, biologists say, by last season’s rains and the arid weather that has since followed.
“It is such a bad, bad weed,” said Sandy DeSimone, a National Audubon Society researcher who scolds and curses artichoke thistle from the 4,000-acre Starr Ranch Sanctuary in Dove Canyon where she works. “You do not want to mess with it, trust me. It is so, so bad.”
Covered with scratchy leaves that rub the skin raw, artichoke thistle is a selfish, hardy weed. Its roots burrow some 8 feet into the ground, hogging water long after rains have subsided. Its twisty branches cast wide shadows on lower-growing plant life, hogging sun. It establishes itself in dense patches, hogging space. One plant is capable of sending hundreds of white, feathery seeds into the air, hogging opportunity.
This year, it has invaded rare breeds of native grasses and wildflowers at an alarming rate, mercilessly choking off the desired species of perennial bunch grass. In the most infested areas of Orange County, the prickly thistle is keeping deer and other wildlife from grazing and hawks from hunting their prey, experts say. At Crystal Cove and other parks, it has seized otherwise graceful meadows, flanking trails and paths.
“The effects of this seemingly beautiful weed are far-reaching,” said Fred Roberts, a botanist for the U.S. Fish and Wildlife Service. “It literally pushes everything out of the way, leaving nothing in terms of other plant life. It has massive suppression power.”
Biologists have been battling artichoke thistle for a century, after European immigrants first brought it here for its celery-like stems, an Italian vegetable called cardoon. But the plant went wild in Southern California’s climate and quickly outgrew its backyard gardens. For more than a decade, it has been listed by the California Exotic Pest Plant Council as one of the 10 most invasive wild land weeds.
The largest stands in Orange County--said to be the most infested county in the state--can be found in San Juan Capistrano, Rancho Mission Viejo, the San Joaquin hills and along both sides of the San Diego Freeway in Irvine. In 1953, biologists estimated about 65,000 acres of range land had been lost to artichoke thistle; today it is likely twice that.
Controlling it is difficult at best. Mowing and pruning have been mildly successful, but the methods tend only to stint the weed’s growth, not eliminate it. Herbicides have had better results, but the long range effects on the environment are unknown. Efforts to find other, nonchemical ways to eradicate the thistle, such as covering the weed with plastic or introducing it to incompatible insects, are also underway by Orange County environmentalists.
“The problem is just digging them up is not an option,” Roberts said. “This weed will put holes in your fingers, right through your gloves. It’s nasty, one of the nastiest for sure.”
At the Starr Ranch Sanctuary, where artichoke thistle occupies about 500 acres, DeSimone is studying the weed and experimenting with ways to save the grasslands. Several research sites are marked off throughout the reserve, which she motors around in a four-wheel-drive vehicle. She has paid for her decision to make artichoke thistle her latest research project with countless cuts and stab wounds.
She hates the weed. She admires it.
“It’s incredibly hard to work with,” DeSimone said. “You can hardly get near it. But that is part of its power. If we don’t get ahead of this thing and do something, it will most certainly win.”