Protecting Stream Health in West Marin

Marin Knotweed Action Team

The Marin Knotweed Action Team (MKAT) is a coalition of various land managers (comprised of local, state and federal agencies and non-profit organizations) who are dedicated to sustaining the vibrant and resilient Lagunitas Creek and San Geronimo Creek watersheds, specifically the control and long-term eradication of Japanese knotweed from these areas. UC Cooperative Extension’s role is to foster a connection between the university and the public by helping to solve problems related to the environment and human and community wellbeing. We strive to be a resource to educate community members about Japanese knotweed and to help landowners identify and manage Japanese knotweed on their land.
Japanese knotweed plant growing by a stream

The Threat of Japanese Knotweed

Japanese knotweed (Fallopia japonica) is a noxious, invasive plant that lives along streams, spreads easily through flood events, and disrupts the environment in the process. It is known to be in San Geronimo Valley since at least 2011, posing a serious threat to environmental and built systems with the potential to cause significant damage to the San Geronimo Creek and Lagunitas Creek watersheds.

Treatment Efforts To Date

All known in-stream populations of Japanese knotweed on private land in the San Geronimo Valley were treated in 2019. These sites ranged in location from San Geronimo to the confluence of San Geronimo Creek and Lagunitas Creek in Lagunitas. The National Park Service and California State Parks are also managing sites on public lands as part of a larger watershed eradication effort.
Number of Japanese Knotweed Sites Treated, By Year
Based upon the experience of other land managers, we are anticipating needing three to five years of treatment to eradicate larger patches of Japanese knotweed. Going into the 2020 treatment season, we are on track to partially achieve this goal as thirteen patches will be getting their third treatment and the majority will be getting their second treatment.
For more information, visit the Marin Knotweed Action Team's website