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More than 200 volunteers gathered last week at the Sepulveda Basin Wildlife Reserve to uproot black mustard, an invasive plant species threatening biodiversity and water quality in the Los Angeles River corridor.
The event, organized by Friends of the L.A. River in collaboration with the California Native Plant Society and the San Fernando Valley Audubon Society, was part of an ongoing effort to restore habitat in the 225-acre reserve. Environmental educators say the spread of black mustard, known scientifically as Rhamphospermum nigrum, is crowding out native vegetation, reducing habitat for local wildlife, and increasing wildfire risk.
“It does look harmless, but it becomes a mono crop, and this is the main enemy to biodiversity,” said Dan Mott, an environmental educator with Friends of the L.A. River. “The native species can’t be here, and all the birds and the insects that are supposed to be in this area, they don’t want the mustard.”
Black mustard, which originates from Europe, Asia, and North Africa, rapidly overtakes native grasses and shrubs. When left unchecked, it forms dense stands that eliminate plant diversity and interfere with natural ecosystem functions.
Its ecological impact goes beyond flora displacement. According to the California Native Plant Society, invasive species like black mustard alter the physical structure of plant communities, reducing their capacity to filter runoff and stabilize soil. This degrades water quality by increasing sediment and nutrient loading into nearby waterways, including the L.A. River.
In addition, black mustard contributes to fire hazards. It dies back in summer, leaving behind dry, flammable stems that serve as fuel for wildfires. This threatens fire-resistant native trees, such as the coast live oak, which can be overwhelmed by intense heat if surrounded by invasive undergrowth.
“If there’s a bunch of invasive species creating fuel underneath it, it’s just kind of burning like a bonfire. It overwhelms the tree’s ability to protect itself,” Mott said.
Volunteers focused on an area with several mature coast live oaks, pulling mustard from beneath the trees and stuffing the plants into 30-gallon compostable paper bags. By mid-morning, mapping software used by volunteer leader Wes Vahradian indicated about a quarter-acre of habitat had been cleared.
“We’ve done pretty solid here, and it’s just a great way for us to kind of measure the impact we’re making,” said Vahradian, a high school senior. “We’ve done it all over the Sepulveda basin.”
Friends of the L.A. River began restoration work in the area in 2019. Mott said the organization aims to clear the most affected zones of black mustard over the next five years. Despite the plant’s tendency to regrow, repeat efforts are showing progress.
Participants included local families, students, and community members. Zia Shaked, 11, spent the morning bagging the extracted invasive mustard alongside her mother and relatives.
“I was just putting the weeds in the bag. I didn’t even notice how much space that was cleared up, and I looked up, like, maybe half an hour later,” she said.
Shanna Shaked, an adjunct professor at UCLA’s Institute of the Environment and Sustainability, said their family volunteers to connect with nature and contribute to local environmental health.
“It felt like a really good way to spend the morning, to be outside and doing something that felt helpful for nature,” she said.
With continued community engagement, organizers believe they can gradually restore the basin’s native biodiversity while also protecting the water quality and reducing wildfire risks across the region.
“I think there was this powerless feeling when the wildfires were happening. You know, we can’t go out there and fight fires ourselves, but this work is actually preventing the spread of wildfires. It’s just something physical, tangible you can do to help the community and help with that problem,” Mott said.
The habitat restoration programs typically attract between 150 and 200 people, according to Mott. However, he has noticed a noticeable increase in participation following the fires that devastated Altadena, Pacific Palisades, and other areas on January 7.
