Invasive knotweeds (Fallopia ssp./Polygonum ssp.)
Invasive knotweeds (Fallopia spp./Polygonum ssp.)

Invasive Knotweeds

Knotweed, poses significant challenges to local ecosystems by invading various habitats, including roadsides, wetlands, and riparian areas. Its aggressive nature contributes to erosion and sedimentation of streambanks, impacting fish habitat and negatively. Additionally, knotweed can damage infrastructure like asphalt and house foundations, potentially decreasing property value. Effective management is crucial, with chemical control often being the most viable treatment for large infestations. Avoid digging, cutting, or mowing knotweed as it can stimulate further spread due to its ability to reproduce from small fragments.

Management Options

  • Knotweed can reproduce through small fragments. Do NOT dig, cut, or mow knotweed as this can stimulate an increased spread!
  • Chemical control is the only viable treatment option for large infestations. Click here for a list of Herbicide Contractors in the Kootenays
  • Do not grow knotweed in your garden or share cuttings of existing plants. Be PlantWise and use Grow Me Instead to avoid planting knotweeds.


  • Native to eastern Asia (Japan, China, Korea).
  • There are three varieties of knotweed (Fallopia spp., Polygonum ssp.) present in our region: Japanese, Giant and Bohemian knotweed. All have similar characteristics and concerns.
  • Herbaceous perennial.
  • Hollow stems, similar in appearance to bamboo.
  • Reach 3 – 4 m height
  • May have small cream, white, or slightly pink flowers.
  • Reproduces vegetatively.
  • Adapted to moist conditions, generally shade-tolerant.
  • Found throughout the region, mainly along roadsides.

Introduction and spread

  • Initially introduced to BC for ornamental use, especially for privacy purposes as it grows rapidly and forms dense patches.
  • The plant reproduces through fragmentation, so when small pieces of the plant are moved by mowers, equipment, or other vectors it can allow the plant to spread.

Consequences of invasion

  • Invades roadsides, disturbed sites, wetlands, riparian areas, and streambanks.
  • Increases erosion and sedimentation of streambanks and riparian areas.
  • Decreases fish habitat and has negative impacts on salmonids.
  • Negatively impacts infrastructure such as asphalt and house foundations by growing through them.
  • May decrease property value.

Status in the CKISS region

  • Knotweed is abundant in some parts of our region, but is not widespread across the entire region. The goal is to contain currently infested areas and to not allow further spread.
  • Himalayan knotweed has not been found in the CKISS region, so it is classified as Prevent. If you have found this species in our region, please report it.

Additional resources