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

Invasive Knotweeds

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.

Description

  • 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 high.
  • May have small cream, white or slightly pink flowers.
  • Reproduces vegetatively.
  • Adapted to moist conditions, generally shade tolerant.
  • Found throughout the region, along roadsides primarily.

Introduction and spread

  • Knotweed was 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

  • Giant, Japanese and Bohemian knotweeds are classified as Contain for the CKISS region on the CKISS Annual Priority List.
  • This means that they are abundant in some parts of our region, but not widespread across the entire region.
  • The goal is to prevent knotweed from spreading to new areas.
  • Himalayan knotweed is considered Regional EDRR in the CKISS region as it has not currently been found in our region.

Additional resources