City Making Progress on Controlling Japanese Knotweed
An inspection this spring (2016) showed that last fall’s (2015) herbicide application to the knotweed infestation resulted in a reduction in the number of knotweed stems and a reduction in the total area covered by the large patch. This is a good result.
However, as expected, new shoots are emerging this spring. The new shoots prove that knotweed has not been eradicated from the area along the SW Bike Path between the Glenway Woods and Forest Hills Cemetery, and demonstrates that a sustained, multi-hear control effort will be required to rid the pest plan from the area.
In a blog post from August 19 2015 , we reported on a commitment by the City of Madison Engineering Division to begin efforts to control Japanese knotweed along the SW Bike Path. A companion blog post on the knotweed situation is re-posted at the end of this article.
Additional Steps Taken
Progress was substantial and promising enough that City Engineering authorized two additional steps that will further recovery efforts. One, a contractor was engaged to apply herbicide to the garlic mustard understory that had been thriving under the Japanese knotweed “canopy”. And two, City Engineering purchased a mix of prairie grass seeds to help compete with the remainders of the knotweed, garlic mustard, and miscellaneous weeds.
The garlic mustard was impacted by the early April herbicide application. In early May, volunteers sowed a mix of prairie grasses in the soon-to-be-former Japanese knotweed patch.
The theory behind sowing prairie grass seed is that if, and when, additional broadleaf-specific herbicide applications are necessary to control the broadleaf pest plants, the chemical will not harm the prairie grass species.
Using Native Plants
This work is not a restoration, nor is it an effort to create a prairie. But, it is a worthwhile effort–using native plants–to help control, Japanese knotweed and garlic mustard, and to prevent their spread elsewhere in the watershed.
This work is also important because it represents an emerging collaboration and partnership between a city agency and neighborhood volunteers to enhance stewardship of a small portion of the Lake Wingra Watershed.
For more background see this post from October 6, 2015 on the control efforts:
City Initiates Multi-Year Effort to Eradicate the Pest Plant
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.
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.
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.