Comments on City plans to control Japanese knotweed

The following comments were sent by Steve Glass, Restoration Ecologist at the UW Arboretum.  He will soon post additional comments on his blog, WingraSprings.

It's good that the City is planning action against Japanese knotweed and other species.

It's good that the City will be hiring knowledgeable and experienced restoration ecology professionals to tackle the pest species.

It's good that the City has mapped out a target area and drawn a line in the sand beyond which the pest won't be allowed to spread.

The proposal is timely, both in terms of seasonal vulnerability of knotweed and the social and neighborhood interest.

  • Clarify what "removal" means.
  • Does the City aim for eradication, or containment (to a specified area) or control (reduction in density and distribution)?
  • Does the City plan to dig out the Japanese knotweed?
  • What does the City envision the site will look like when the pest species have been replaced by desirable vegetation?
  • What is the plan to replace the pest species with desirable vegetation?
  • What are the plans for erosion control on steep slopes where knotweed now dominates?
  • There are existing prairie plantings along the path. These have been planted by neighborhood associations and volunteer groups with the support and approval of City Engineering.  What are the plans to protect these areas from pest plant control efforts?
Once established, Japanese knotweed is extremely difficult, if not impossible, to eradicate. Some actions such as repeated mowing or herbicide application can be somewhat effective but these must be carried out consistently and persistently for several years.

  • Volunteer groups stand ready to help.
  • Contain the spread by adopting management practices (mowing, snow plowing, excavation) that avoid spreading the plant or making the situation worse.

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