T’Sou-ke Nation leads collaborative effort with District of Sooke and Capital Regional District to manage invasive knotweed in Sooke River system

The T’Sou-ke Nation, with support from the District of Sooke and the Capital Regional District and in coordination with the Province of B.C., has applied for a Pesticide Use Permit to support limited, targeted management of invasive knotweed located in and adjacent to the Sooke River system, including the Sooke River and tributary rivers such as the Charters River. 

Knotweed is considered one of the world’s worst invasive plants. It spreads aggressively through underground stems, known as rhizomes, as well as small root or stem fragments. New plants can grow from fragments as small as half a centimetre, allowing knotweed to spread quickly through water currents, soil movement, garden waste, equipment, tools, vehicles, boots and clothing. 

Along the Sooke River system, knotweed is currently limited to approximately 0.15 hectares across a 2.3-kilometre stretch, from the confluence of the Sooke and Charters Rivers downstream toward the ocean. Without treatment, knotweed has the potential to spread further along the Sooke River and estuary, where it can displace native vegetation, increase erosion, degrade water quality, reduce fish habitat, obstruct flows, affect infrastructure, and limit access to water for wildlife and recreation. 

Since 2019, staff from the T’Sou-ke Nation, District of Sooke and the Capital Regional District have conducted inventories of the Sooke River knotweed populations and worked with provincial staff to assess options for managing knotweed in the Sooke River system.  Ongoing knotweed management has shown that sustained, targeted treatment can significantly reduce or eradicate infestations over time. This application represents the next step in that work, seeking the approvals needed to address knotweed in and adjacent to the Sooke and Charters Rivers, where treatment requires additional consideration due to the sensitivity of riparian and aquatic environments. 

“Caring for the Sooke and Charters Rivers is part of caring for the lands, waters, salmon, wildlife and future generations that depend on them,” said Chief Larry Underwood, T’Sou-ke Nation. “By leading this work with our partners, T’Sou-ke Nation is seeking approval for a careful, targeted approach to prevent invasive knotweed from spreading and to support the long-term health of these important river systems.” 

“The Sooke River is central to our community’s identity, environment and quality of life,” said Mayor Maja Tait, District of Sooke. “The District is pleased to support this careful and coordinated approach, helping protect the river system for residents, visitors and future generations.”  

If approved, the proposed 2026 to 2029 treatment program would allow for targeted treatment of knotweed detected in or adjacent to the Sooke River system. Treatment methods may include targeted foliar application and, where required, stem injection. Applications would be conducted as targeted spot treatments to limit drift and reduce impacts to non-target vegetation. Drift shielding, such as tarps, may also be used where appropriate. 

Initial treatments are anticipated in July and August 2026. If approved, subsequent treatments may occur up to twice per year in summer through 2029, during seasonal low water levels and active plant growth. 

River-based knotweed management has been successful in other areas of Vancouver Island. The Nimpkish River knotweed management project, which began in 2018, has seen the total impacted area and knotweed extent decline by approximately 90 per cent, from 1.65 hectares in 2019 to 0.1704 hectares in 2024. 

A draft copy of the application and maps of proposed treatment locations can be viewed online at https://tsoukenation.com/invasive-knotweed-control.  

For more information, please contact the T’Sou-ke Nation at admin3@tsoukenation.com or the BC Ministry of Forests at invasive.plants@gov.bc.ca with subject line “Sooke River Knotweed PUP #402-0694-25-28.”