Gorse: We Burned This Highly Invasive Plant, Here’s What We Learned

By Matt Dolkas, Senior Manager, Marketing

April 28, 2025

Standing on the edge of a thick sea of yellow flowers, a Marin County rancher surveys a corner of their 588-acre ranch in northwestern Marin County. The bright spring blooms decorating much of the landscape seem picturesque at first glance, but this thorn-laden plant known variously as gorse, Irish whin, or furze (Ulex europaeus) is a highly invasive species that is consuming the family ranch and much of the lower Walker Creek watershed.

“We’ve tried mastication (grinding it to the ground with heavy machinery) and a few pesticides, but we haven’t yet found a solution we can scale across this large of an area,” a family representative explained. “The other side of the ranch is covered in this stuff, we have to find a solution.”

But on this warm spring day, the battle against this invading legume shifts in the family’s favor. With support from MALT, a team of fire experts from Fire Forward—an innovative program of Audubon Canyon Ranch dedicated to bringing “good fire” back to California landscapes—along with one tribal member from the Federated Indians of Graton Rancheria had gathered to experiment with burning this noxious weed.

What’s Wrong with Gorse?

Beyond consuming valuable rangeland, gorse creates a cascade of problems for both agricultural and ecological systems. The plant’s formidable defensive strategy—densely packed branches covered with needle-sharp thorns that can penetrate work gloves and clothing—makes it physically dangerous to handle. “You literally can’t even walk through it,” the rancher said, gesturing to a nearby patch. Left unchecked, the plant slowly consumes biologically rich coastal prairie habitat with the invasion now estimated at over 200 acres across Marin County.

Perhaps most concerning for California’s fire-prone landscapes is the plant’s extraordinary flammability in the summer months. Gorse contains volatile oils that make it much more flammable than most native vegetation. In its native range in western Europe, gorse fires have been known to burn so hot they sterilize the soil—yet ironically, this super-heated environment often triggers mass germination of gorse seeds, creating a vicious cycle of fire and reinvasion.

Testing A New Approach – Winter and Spring Prescribed Fire

This prescribed fire was an experiment in timing, working to find a new window of opportunity to exploit the plant’s biological vulnerabilities. “Contrary to popular belief, a lot of shrubs in California have really low fuel moisture in the winter,” explained Brian Peterson, the Interim Director at Fire Forward and the fire ecologist leading the day’s burn. “During winter months, when the plant is not actively growing, it doesn’t draw water up from its roots, resulting in surprisingly dry fuel in the middle of the wettest season.”

Burning in the winter months could give land managers a new window for controlling gorse that hasn’t been traditionally utilized. The winter also provides safer conditions, with wet grass serving as natural fuel break lines in the landscape—it’s exactly the type of scalable solution that landowners desperately need across the Walker Creek watershed. Burning this acre-sized patch was an opportunity to test this timing.

Burning Insights

Dr. Peter Nelson, a member of the Federated Indians of Graton Rancheria and professor at UC Berkeley, had the honor of starting this fire—likely the first fire started by a Coast Miwok tribal member on this corner of ancestral land in over 200 years. It was a profound moment watching the orange flames chase through the dense thickets of this European invasive species, a warm gesture to the Indigenous practices that maintained this landscape for millennia prior to colonization.

For the crew supporting the day’s fire, there was a deep sense of satisfaction in watching the small area of gorse be consumed in flames, a new chapter for this ground emerging before our eyes. But while flame lengths reached impressive heights of 30 feet in some areas, many sections of the gorse patch didn’t burn completely, leaving the flowering stems exposed. The team discovered that the plant was too wet, despite the dry period in the days leading up to the burn.

“It was clear that the window to burn gorse should actually be earlier in the winter when the plant is drier,” Brian noted. This was the day’s most valuable lesson: December or January likely offers optimal conditions for gorse management burns, challenging the conventional spring timing that had proven less effective.

While the burn wasn’t a silver bullet, it offered some compelling proof that fire has real potential as a tool for tackling gorse. Even though the flames didn’t take out every plant, the way the gorse responded showed that—under the right conditions and timing—prescribed fire could play an important role in a broader, integrated strategy to manage this invasive species.

Many Hands, Light Work

Beyond the implications of this experiment, this collaborative burn was a great example of the kind of flexible, partnership-driven land management we need more of—especially as we face mounting challenges from climate change. It’s this blend of traditional ecological knowledge with modern fire science, the wide range of partners and expertise, and the can-do attitude of the ranching community that is helping to chart a new course for ecological restoration.

The insights gained from this experimental burn won’t just stay on this ranch—they’ll help shape future efforts to manage gorse throughout the region and on many MALT-protected ranches. With this new understanding around timing and technique, upcoming burns will be even more effective in pushing back against one of California’s most stubborn invaders and restoring balance to Marin’s coastal grasslands.