Japanese Knotweed

Japanese Knotweed:

Japanese Knotweed is amongst the most difficult plants to control. This plant has the potential to impact homes, roads, parking lots, and other infrastructure.

It can grow to 2.1m (7ft) tall, resembling bamboo. Leaves are shovel shaped while the canes have characteristic purple flecks and die back to ground level in winter.

What the City of Chilliwack is doing about Japanese Knotweed:

  • Public education and outreach with the goal of reducing the spread of Japanese Knotweed and other invasive plants.
  • The Environmental Services Department is mapping locations of Japanese Knotweed on public property. This information is used to help the road-side mowers avoid cutting and spreading patches of Japanese Knotweed.
  • The Operations Department is using a mild herbicide spray to control Japanese Knotweed in critical areas of public property. Control trials at locations in Chilliwack are also being conducted by the Fraser Valley Invasive Plants Council through the FVRD. Control is difficult and slow as it can take several treatments and inspections over multiple years to ensure the roots are killed.
  • The City is collaborating with other local and regional governments, as well as environmental organizations, to develop effective and coordinated control programs in our region.

How can you control Japanese Knotweed?

Residents that have confirmed patches of Japanese Knotweed on their property can consider the following control options:

  • Never dig, mow or weed-eat Japanese Knotweed. This will only make the problem worse as knotweed can regenerate from stem and root fragments as small as 1cm.
  • Manual Control: Mature stems can be repeatedly cut at the base with a single clean cut using a knife, pruning shears, etc. This process may need to continue for up to five years to exhaust the energy stores in the roots.
    • Cut material can be bagged and taken to the Parr Road Green Depot for disposal ($7.50 for up to 100kg). Keep invasive plants separate from other yard trimmings and notify the scale attendant; they will handle the material separately.
    • Cut material can be bagged and picked up by the FVRD for safe disposal by calling 604.702.5067. Please clearly label the bags and refrain from having them collected on the same day as your Curbside Collection of garbage and recycling.
    • Cut material can be laid on an impervious surface (ex: driveway or tarp) to dry in the sun. When crispy and brown the material can be included in curbside Green Cart, backyard compost, or burnt where/when applicable with a permit.
  • Chemical Control: Herbicides, when used by a trained professional, are an effective method of controlling knotweed. Special care must be taken when near a watercourse and to avoid non-target vegetation. Herbicides with the active ingredients glyphosate, imazapyr, or triclopyr are known to be effective. Chemical control may require two applications per year for multiple years to control the plant.

To learn more about Japanese Knotweed or other invasive plants, call the City of Chilliwack’s Environmental Services Department at 604.793.2907 or visit the websites below:

Fraser Valley Invasive Plant Council

Invasive Species Council of BC

Provincial Invasive Plant Program

Fraser Valley Regional District: Invasive Weeds