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KNOCKOUT KNOTWEED

Japanese Knotweed is an invasive species that was introduced from eastern Asia. This rapid-spreading and dense vegetation shades out native plants, and its shallow root system creates large areas vulnerable to streambank erosion. Additionally, knotweed can reproduce and spread from even small fragments.

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This summer, the Missiquoi River Basin Association (MRBA) is conducting experiments to assess various ways to control this invasive species through mechanical means (smothering, cutting, and wire mesh to choke the plant). These experiments are set up as five 8'x10' treatment plots and a control plot, and are occurring at three locations throughout the watershed. MRBA staff are collecting data at these locations weekly. Timelapse photos, weights, and stem counts will give us a sense of how effective each treatment is against knotweed.

One of the treatment locations is in Riverwalk Park in Montgomery - stop by and see our experiment in progress:

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Japanese knotweed treatments plots:

Metal mesh - choking:

1/2 inch hardware cloth was staked down over a knotweed patch, crushing any stems present. Knotweed stems will then grow through the grid; once they get large enough, the stems will girdle or choke themselves in the mesh, killing the stem. Being forced to continually regrow will deplete the rhizome of the plant. 

Smother methods:

A thick layer of cardboard was laid down over a knotweed patch (crushing any stems present), and a 4-inch thick layer of wood chips was layered on top of this.

At a second smother plot thick (45mil) pondliner was staked over a knotweed patch, crushing any stems present). We will monitor any growth that may appear in these plots.

Cutting methods:

We will cut all stems within one plot down the ground weekly, weighing the cuttings each week.

We will do a similar treatment at another plot, though only cutting monthly. 

*With these cutting methods, it is very important to be sure that no cut stems, leaves, or certainly roots, get transported  - new knotweed can grow from just about any  part of the plant! Cuttings must be carefully dried in a fashion that does not allow them to spread to reduce their viability.

Control plots will only be cut at the end of the growing season.

Other Knotweed treatment efforts: 

Our partners at the Upper Missisquoi and Trout Rivers (UMATR) Wild & Scenic Committee are offering small grants to landowners who are committed to using mechanical methods to treat a patch of knotweed on their property. Learn more here: https://www.umatrwildandscenic.org/knotweed

Our thanks to the Lake Champlain Basin Program for the Aquatic Invasive Species Spread Prevention grant that is supporting this project!

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This project has been funded wholly or in part by the United States Environmental Protection Agency (EPA) under assistance agreement (LC - 00A006950) to the New England Interstate Water Pollution Control Commission (NEIWPCC) in partnership with the Lake Champlain Basin Program (LCBP). NEIWPCC manages LCBP’s personnel, contract, grant, and budget tasks and provides input on the program’s activities through a partnership with the LCBP. The contents of this document do not necessarily reflect the views and policies of NEIWPCC, the LCBP, or the EPA, nor does NEIWPCC, the LCBP or the EPA endorse trade names or recommend the use of commercial products mentioned in this document.

Connect with us via phone or email if you have questions about our project, or knotweed in general!

How I feel about knotweed.