Planned Management of Invasive Black Knapweed in Metchosin

An invasive species that can put natural meadows and farmland at risk will once again be knocked back this year in Metchosin.

Black knapweed (Centaurea nigra) is what’s known as a tap rooted perennial and can form dense monocultures which displace native vegetation. It can also be a serious pest in agricultural crops and can increase the risk of fire. This highly invasive plant species is thankfully restricted to a small number of sites in Metchosin and is regularly managed collaboratively by the District of Metchosin and CRD Regional Parks.

Black knapweed can be found at both Devonian and Witty’s Lagoon Regional Parks, including in the fields along Metchosin Road, but the largest populations are at Tower Point. There are populations in the park, but also on road right of ways and ditches and on some private properties near Tower Point and on Duke Road.

As has been the case for a number of years now, a variety of methods will be used to manage Black knapweed at CRD Regional Parks in Metchosin in 2023. These methods include selective mowing, seed head removal, and a single targeted chemical treatment between June and August with triclopyr. A licenced applicator will apply the treatment under the direction of CRD staff. Treatment will occur in accordance with all provincial guidelines, during a period of low winds and without forecasted rainfall to increase the effectiveness and to reduce potential negative environmental impacts. This year a blue dye will also be used help the applicator easily identify areas that have been treated. The dye is harmless, dissipates quickly with sun exposure and won’t affect clothing or pets. In CRD Regional Parks, chemical treatments are only employed after a determination that there is no effective alternative treatment and that the treatment has minimal environmental impact.

Impacts to park users from all black knapweed management methods are expected to be minimal and signage within regional parks will be installed both before and during management actions. All untreated areas of parks will remain open during and after treatments. CRD staff will fence areas undergoing chemical treatment to prevent access by people and dogs and will keep fencing up as a precautionary measure for three to five days following treatment. People and animals can continue to safely use unfenced areas of parks during regular park hours.

As was done in past years, the CRD will also conduct post-treatment effectiveness monitoring. Annual information on treatment effectiveness supports an adaptive management approach in which land managers continually assess and improve treatment methods to effectively manage black knapweed infestations.

Metchosin residents can help by keeping an eye out for this harmful plant and by reporting it when seen and controlling it on private property. Control of black knapweed on private property outside of regional parks is the responsibility of individual landowners. For more information on black knapweed in regional parks, contact Conservation Biologist Jen McEwen at If you need advice regarding control of this species on private property, contact Jenny Eastman, Regional Invasive Species Program Coordinator at