It doesn't take a botanist or even a nature nut to identify yellow star thistle along a favorite hiking trail. Every outdoor enthusiast has felt the familiar stab of introduction.
The invasive weed can reach 6 feet high with stiff limbs that seem to sprout daggers from every pore. Each arm is topped with a crown of inch-long spikes and one showy yellow flower that seem perfectly placed to stab a shoulder or poke an eye.
Yellow star thistle is public enemy No. 1 in the California weed world, found in every county but one and covering as much as 14 million acres. It is blamed for altering native landscapes, turning meadows into deserts and even killing horses, which are uniquely vulnerable to a toxin in the plant's leaves.
"Yellow star thistle is kind of like the state weed," said Doug Johnson, executive director of the California Invasive Plant Council, a nonprofit research group. "There's tons of it."
A coordinated effort across 14 counties has made strides in recent years to keep star thistle out of the Sierra Nevada, one of the few California regions the weed has not yet penetrated entirely. But now star thistle appears poised to win that battle, too, with a powerful ally on its side: state budget cuts.
The Star Thistle Leading Edge Project was funded by the state Department of Food and Agriculture as part of its weed control budget totaling $2.7 million in 2011. The money funded county weed management agencies statewide, as well as coordination among Sierra counties from Plumas to Kern, which jointly drew a line at about the 4,000-foot elevation mark to combat star thistle.
All that money was cut from the 2011-2012 state budget cycle.
Over the past year, the Leading Edge Project cobbled together local and federal dollars, including grants from the U.S. Forest Service. But that money runs out next month. The project sought a $314,000 grant from the Sierra Nevada Conservancy to continue the work for four years. But it learned Thursday the grant will not be funded because the group failed to meet the application requirements.
The result? Weed experts say yellow star thistle could begin to crowd out native plants in the Sierra, becoming a common sight and literally a thorn in the side for hikers, cattle ranchers and other nature lovers who enjoy the mountains as they are, free of this prickly nuisance.
"Walking through it is totally miserable. It's a terrible plant," said Garrett Dickman, a botanist and biologist at Yosemite National Park. "I deal with quite a variety of nonnative plants, and I try to be professional about them. But I personally dislike yellow star thistle. I've been jabbed by it so many times. It's a really easy plant to hate."
A notorious hitchhiker
Star thistle is one of the earliest invasive species in California. A native of the Middle East, its seeds are believed to have reached California by hitching a ride in shipments of alfalfa seed from Chile during the Gold Rush.
The alfalfa was planted as animal feed in the Sacramento Valley. Star thistle, with bristly seeds that cling readily to most anything, spread across the state in the same manner: by hitching a ride in alfalfa bales and sticking to animals and clothing.
More recently, the plant has advanced by riding along on trucks and bulldozers, infiltrating gravel shipments and hiding in erosion control devices that consist of straw bound into tubes.
It is hard to find anything to like about yellow star thistle.
Before leafing out much on the surface, the plant shoots its roots down as deep as 6 feet to find moisture, then proceeds to hog it all. This means it can, over time, eliminate even oak forests, which grow in much the same manner and need that deep moisture to propagate seedlings.
"It would be as if these areas are experiencing drought because of the amount of water it uses," said Joe DiTomaso, a weed ecologist at UC Davis and a leading expert on star thistle.
The plant blooms annually in spring, and once it begins sprouting surface growth, its prickly arms grow so dense that they shade out other plants, leading to a field of nothing but star thistle.
One result is that a field will lose native surface growth, such as grasses, flowers and forbs, that capture rain and snowmelt, allowing it to filter into the ground. Instead, runoff moves across the land much faster in a star thistle field, causing erosion.
When star thistle goes to seed, it does so with a vengeance. A single large plant can produce more than 100,000 seeds, which can survive as long as five years in the soil, waiting for optimal growing conditions.
Then the adult plant dies, leaving a spiky mess behind for grazing animals and any hikers or cyclists who might come by.
The plants also pose a fire hazard. Not only are they dried up and primed to burn, they have crowded out native plants that might have been more fire-resistant.
"We're talking about a major natural resource problem, not just an agricultural problem," said Johnson.
Holding the line
The Leading Edge Project started about a decade ago with a mapping effort to find out just how much of the state was infested with star thistle, and where it was spreading, said Wendy West, the project's coordinator and a University of California Cooperative Extension adviser based in Placerville.
"It felt like such a losing battle that we really needed to prioritize what we could do and how we could be successful," West said.
For years it was thought star thistle was unable to grow at mountain elevations, partly because it does not tolerate forest shade. But the mapping effort showed otherwise, revealing isolated star thistle populations in the mountains.
"I've personally pulled plants at 7,000 feet in Alpine County," West said. "It may not move quite as fast, but yellow star thistle is a really good example of a plant that can adapt to new locations easily."
The program turned to coordinating weed management efforts in the mountain counties to hold the 4,000-foot line and attack "outlier" thistle populations that appeared beyond it.
The work is not complicated or expensive. It amounted to less than $10,000 per year in each county, West said, to hire seasonal labor crews in the spring to attack star thistle mainly with herbicides before it goes to seed.
But the work must be done annually at every site for three to five years, because the seeds are so long-lived.
"When we had money, we were able to hold the line," West said.
Much of the work has concentrated on highway corridors, a common route of the star thistle's advance. The plant often attaches itself to vehicles or road construction materials, puts down roots in a freshly cleared road shoulder, then advances uphill.
Key corridors include Highway 50 and Interstate 80, which lead to Lake Tahoe. Another is Highway 140 in Mariposa County, the gateway to Yosemite National Park.
For several years, Dickman has battled a 300-acre field of star thistle along Highway 140 near El Portal. Some of the plants have already moved onto national park lands at the site, which includes slopes so steep that spraying crews hang from ropes like rock climbers to attack star thistle on canyon walls.
The mapping effort, as of last year, identified 586 "outlier" star thistle populations that have already jumped across the Leading Edge line and edged higher into the Sierra. Without treatment, these will likely become the origins of new infestations.
Johnson has prepared a strategy that estimates $1.5 million is needed annually to go after high-priority invasive plant infestations, with star thistle as a leading target. He doesn't yet know where the money will come from.
"The program is kind of on life support," Johnson said. "It really puts our gains in jeopardy, because these are long-term efforts. That's the fear: That you're going to lose the battle."