Across the region, goatheads - or puncturevine - are a scourge to cyclists, walkers and our four-legged friends: they pop tires and embed themselves in shoes and sensitive paws. There are many efforts to halt their spread, and new research could help to better target that work.
A group of people in Veterans Memorial Park - mostly volunteers - were armed with hand tools, their orange utility buckets steadily filling with thick mats of goathead’s snaking vines. The plant's signature, corn-kernel sized nutlets, which contain several seeds, sport thumbtack-sharp spines.
The group is part of Boise’s Weed Warrior program, which fights back against invasive plants. They’re united by hatred of goathead, which is also known as puncturevine.
“A goathead is an evil mean vine,” said Parks and Recreation employee Mike Burkhart.
“I am a cyclist, I hate goatheads,” said volunteer Mark Poppler. “I've been fighting them for probably 10 years on my own, I was really happy to find this group to fight them as a group.”
“It's definitely an act of vengeance,” fellow volunteer Kathy Brummund said. “But like I said, when you're looking for them and you're trying to dig them up, they're a lot harder to find than when you're actually on your bicycle running them over.”
As the volunteers yanked out weeds, a group of dog walkers was finishing up. Abigail Jungen was with her pooch Cedric, who’s well acquainted with goatheads.
“He's gotten them stuck in his feet. He's gotten them stuck in his hair. They pull on him,” Jungen said. “He has crazy paws that, like, suck them in.”
She added: “A hater. I'm a hater for goatheads.”
For his part, Cedric barked aggressively when asked for his take on goatheads, to the nods and agreement of others.
Boise is full of people – and pets! -- with strong feelings about goatheads. There’s even an annual summer festival that celebrates removal efforts. And at Boise State University, researchers have developed a new tool that promises to make removal work more effective.
Turning science into action
Just off a downtown Boise parking area, an undeveloped lot was baking in the midday sun.
There’d be little reason to notice it – unless you care a great deal about goatheads, like Boise State associate biology professor Trevor Caughlin. He typically does his fieldwork in far-flung places – but then the pandemic started in 2020.
“We were in Boise that whole summer and so we needed a project and we looked around and we realized that here is this plant that's causing a lot of harm to Boiseans, the community really cares about goathead and we thought, why not study that plant?” he recounted.
At randomly selected sites across the city, his lab team rigorously documented the presence – and absence – of the invasive plant. They found that lower property value was the most important predictor of goathead abundance, suggesting that poorer residents are disproportionately impacted by them.
“We're not sure exactly why, but we are very concerned about the equity implications of that relationship for people that rely on bicycles for transportation,” Caughlin said. “Or even for people that would like to take advantage of the recreational opportunities that bicycles provide and that Boise is so great at providing, but maybe inhibited from doing that by having flat tires.”
Beyond that equity issue, the paper notes that “puncturevine populations that are overlooked in removal efforts, such as low-valued properties, could undermine eradication efforts as seeds from neglected patches re-colonize managed patches.”
Caughlin and the team also produced a map of likely goathead hotspots, helping groups like the Weed Warriors better target their efforts.
“The map is a way to translate our science into action that hopefully benefits the community,” he said.
Teresa Fong, an undergraduate member of Caughlin’s lab, said the map makes scouting promising volunteer removal sites “a lot easier.”
A lightbulb moment
With goathead so prevalent across the West, Caughlin’s work has caught the eye of other researchers – like Amanda Stahlke, an incoming biology professor at Colorado Mesa University in Grand Junction.
“As a cyclist, I became acquainted with goatheads,” she said.
She also studies invasive plants and biocontrol methods – like a weevil that feeds on developing goat head seeds.
“It was just a lightning moment for me or a light bulb moment,” she said of Caughlin’s research. She added, “It's really helpful to have a targeted intervention rather than spreading resources really thin… I think that they've created a recipe for success.”
She said she’s already been in touch with the local trail community and city council members about the possibility of replicating the work in Grand Junction.
Everyone is a weed warrior
At the Boise lot, Caughlin and two lab members – Fong and doctoral student Richard Rachman – were crunching through the brush.
“There's cheatgrass, tumbleweed,” Rachman said. “There's a goathead, there's a goathead, there's a goathead.”
“This abandoned lot is a goathead hot spot,” Caughlin chimed in.
Caughlin meant that literally. It was not one of the study sites, but it glowed brightly on the map they generated.
Back on the sidewalk, they lifted their footwear to find the soles blanketed. Fong used keys to scrape them off, and Caughlin observed that “it's definitely validation of our hotspot map that now we've walked through this patch and our shoes are covered in goathead fruits.”
“Anyone can be a weed warrior: you can go to themap, you can find a location and you can contribute to curbing the spread of this noxious weed,” he said.
All you need, he said, is a pair of gloves, a digging tool that can get down to the roots and a plastic bag to properly dispose of the resilient vine.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
