How Los Altos Hills took on an invader

Town and residents fight to control a noxious weed

Stinkwort grows along a traffic median near the on-ramp to Interstate Highway 280 on Foothill Boulevard in Los Altos. Photo by Veronica Weber.

• This article is part of a larger story on the "Invasion of the stinkwort." Read the article here.

Los Altos Hills is known for its rolling hills, large properties and pastures. But when the invasive stinkwort plant threatened to transform the town, residents and the city geared up for a war.

The small Christmas-tree-shaped weed growing street-side started to spread into open space about two to three years ago, threatening the bare legs of bicyclists along trails and, if left unmanaged, to overrun the town's open space.

The stinkwort — named for its camphorous smell and sticky resin — is considered flammable and has been known to sicken livestock. In people, it causes contact dermatitis. Producing many thousands of seeds per plant during the late summer and fall when many native plants are dormant, stinkwort, like other invasive species, can potentially create a botanical monoculture, wiping out food for animals.

Members of the town's Open Space Committee and town officials took an "it takes a village" approach to combat the weed. Volunteers mapped the weed's location on every street. With the help of Palo Alto nonprofit group Grassroots Ecology, volunteers then went to Byrne Preserve and along pathways and roads to pull out stinkwort plants by hand or cut the plants below the ground to kill their roots.

The committee and the town produced and distributed a mailer with pictures and instruction on how to properly remove the plants from private property, which went to every home, said Kit Gordon, open space committee co-chair.

"We've aggressively attacked it," she said.

As a result, unlike many other invasive weeds that have spread throughout the state, Los Altos Hills is controlling the stinkwort.

"We've seen huge patches disappear by neighbors taking care of it themselves," Gordon said.

The town itself spent nearly $15,000 last year to control the plant. Armed with the volunteers' map, in September a contractor sprayed an herbicide that is not toxic to aquatic life on more than 10 miles of roadsides throughout town, said Allen Chen, public works and engineering director. The town sent a letter to homeowners regarding the spraying and allowed them to post a "Do not spray" sign on their road frontage if they were committed to removing any stinkwort themselves, he said.

For Gordon, the goal is to keep on top of the plants before they become an intractable problem. Besides roadsides, the construction boom also offers the stinkwort fertile ground, since the weed readily colonizes disturbed soils, Gordon said.

When volunteers mapped out stinkwort, they saw that where new homes had been built, stinkwort had moved in. And in areas where landowners disk the soil for firebreaks, stinkwort, which is a flammable weed, makes itself at home, ironically, she said.

Even Gordon's home became the unwitting harborer of the resourceful weed.

"When my own property had a small landslide, in the bare dirt guess what was growing on there?" she said.

Gordon thinks that municipalities need to look at their policies regarding invasive weeds. The Los Altos Hills Town Council has directed the open space committee to work on a policy for people doing construction to eradicate stinkwort before it goes to seed.

"When a house is under development, it should be part of the condition of approval," she said.

Municipalities can also enforce state noxious-weed laws and local weed-abatement ordinances to get private property owners to control infestations, she noted.

Gordon and her committee want to educate residents not only on stinkwort removal but on other invasive weeds through additional handouts, she said.

Committee members have also approached the California Department of Transportation (Caltrans) about controlling and eradicating stinkwort on state property Interstate 280. Gordon said her committee is pushing to get something else planted that would keep the weed from taking hold.

Stinkwort sneaks past most land-management eradication schedules. It flowers in September and sets seeds in December and January.

Chen said the town plans to continue to manage stinkwort. The town wants to get an earlier start next year, catching the annual plants as they emerge from the soil or when they are younger, he said. Stinkwort seeds are viable for only two to three years. Killing off any emerging plants before they set seed could eventually deplete the soil seedbank and limit the plant's spread.

More information about stinkwort and native plants


Berkeley-based nonprofit website with maps, photos, descriptions and information about native and nonnative plants in California. Interactive database allows users to search for plants and to add their observations. Sortable by plant life form, soil type, locality and more.

California Invasive Plant Council

Nonprofit organization based in Berkeley dedicated to protecting California ecosystems from invasive plants. Offers ratings systems for invasiveness of all weeds. The Cal-IPC Inventory link under "Plants" allows users to search for invasive plants by name, region, habitat, map, etc. WeedMapper allows users to drill down to locales and whether the species is under control. Offers photographs and a species ID card link for identification and describes ease or difficulty of removal. References to scientific literature.

Town of Los Altos Hills

Los Altos Hills provides a flyer alert on stinkwort that can be used to help residents identify the plant and discusses basics for its removal.

Watch "Behind the Headlines" for a discussion of stinkwort with ecologist Claire Elliott on this issue here.


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