Madison Tackles Japanese Knotweed Along SW Bike Path

City Initiates Multi-Year Effort to Eradicate the Pest Plant

Informational sign announcing the City's multi-year effort to eradicate Japanese knotweed.

Informational sign announcing the City’s multi-year effort to eradicate Japanese knotweed along a portion of the SW Commuter Bike Path.

In August of this year, contractors hired by the City of Madison Engineering division, began a concerted effort to contain two large, well-established Japanese knotweed patches along the SW Bike Path.  The largest knotweed patch is below the bike path between Glenway Street and Virginia Terrace; a second, smaller patch, is between Odana Road and the bike path.  The herbicide application this summer followed a trial period the past two summers in which small test applications of herbicides were used to decide appropriate methods and effective techniques. City of Madison Engineering Division has management responsibility for the bike path corridor. We first reported on the City’s control effort in an earlier blog post.

The area where a chemical was applied to the knotweed was fenced off to protect the public.

The area where a chemical was applied to the knotweed was fenced off to protect the public.

Reasons for Eradication Effort

Japanese knotweed (Fallopia japonica); also known before as Polygonum cuspidatum, is a vigorous perennial plant that spreads through rhizomes and is adapted to growing along waterways and in poor, rubble-strewn soil. The reddish, hollow stems, about the size of your wrist, can grow up to 4″ per day and reach a height of 10 to 12 feet, or more. The stems grow with such force that they can push up through asphalt and does not respect property boundaries. An established clone can spread to cover many acres and will continue to do so unless contained.

Little, except other non-native pest plants, grows under a knotweed clone.   A knotweed clone has little wildlife habitat value and can easily choke out desirable native species, clog storm water channels, and riparian areas along streams and lakes.

Threat to Lake Wingra, its Wetlands, and the Arboretum

Especially troubling about these two knotweed clones is their position directly upstream of valuable natural areas and restorations in the nearby lowlands.  There is the potential for knotweed stem and root pieces to be carried downstream on storm water and enter the wetlands surrounding Lake Wingra, and ultimately the Arboretum with its irreplaceable natural areas and long-established restorations.

An area of Japanese knotweed (brown patch in background) that has been killed by herbicide application.

An area of Japanese knotweed (brown patch in background) that was killed by herbicide application.

Response by City

The City of Madison became aware of the knotweed problem when alerted by citizen volunteer stewards of the bike path, who have planted and tending prairie plantings along the path for more than 10 years.  The knotweed eradication effort is a response by the Engineering Division to these citizen steward concerns that 1) the pest plant poses a threat to native plantings along the path; 2) to physical infrastructure and backyards along the bike path;  and 3) to the natural areas surrounding Lake Wingra and to the restorations in the Arboretum.

Stay tuned for further updates on the progress of the City’s eradication effort.







About Steve Glass

The blogger is a restoration ecologist, Certified Ecological Restoration Practitioner (#0093 SER) and writer living in the Midwestern United States.
This entry was posted in City of Madison Engineering Division, invasive plants, Japanese knotweed, Lake Wingra Watershed, Restoration ecology, SW Bike Path and tagged , , , , , . Bookmark the permalink.

2 Responses to Madison Tackles Japanese Knotweed Along SW Bike Path

  1. Gary Shackelford says:

    Could you point me to a source that gives details of the technique used to try to eradicate the knotweed along the bike path? We have been helping a neighbor in his attempts to remove a large patch of Japanese knotweed, and we are always on the lookout for a better method.

    We have used a formulation of glyphosate approved for aquatic application (53.8% a.i.), diluted 1:1 with water, to which we add surfactant as well as marker dye. Our technique is to hand-cut the robust hollow stem just below the second node and to apply herbicide to the cut stem, allowing some of the chemical to drip into the hollow.


    • Steve Glass says:

      HI Gary,
      The technique you are using sounds like a sensible and effective approach. The contractor that worked along the bike path used, I believe, a foliar application of Milestone herbicide (aminopyralid). Its use is described in this information sheet from UW Extension: information sheet

      You probably know of this resource but if not it’s worth looking at as it is the most comprehensive and up-to-date discussion of control methods for Japanese knotweed.

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