Japanese Knotweed Control

If you have been out visiting the Copetown Summit Bog parking lot along the rail trail recently, you will have noticed that our staff have been busy at work removing a population of invasive Japanese Knotweed.

What is Japanese Knotweed?
Japanese Knotweed is an invasive and aggressive, bamboo-like plant that causes erosion, degrades wetland and riparian habitat and is even capable of growing through concrete. This invader is not only very harmful to biodiversity, but to public and private infrastructure too.

Staff have been using the tarping method to help control the Knotweed, and this season decided to upcycle and reuse the boat shrink wrap from the boats at Fifty Point Conservation Area. Boat shrink wrap is used to wrap boats over winter and is a hard-to-recycle material that typically ends up in the landfill.

What is the tarping method?

Tarping is done by chopping down the Japanese Knotweed and then laying tarps over the area to “cook” and block the sun from reaching the root system. Tarping is typically done with black material to help attract the sun.

Chopping down the knotweed

In a dense stand of Japanese Knotweed, you typically find old and new stalks growing in clumps with no other vegetation. This made it easy to chop down all the stalks without having to worry about trampling native vegetation.

Stalks were cut as close to the ground as possible and not pulled because pulling can disturb the soil and break apart the rhizomes (the root). Staff were careful to ensure that no pieces of the plant were left behind.

Disposing of old vs. new stalks

Old and new stalks are disposed of separately because they pose different risks.

  • Old stalks were piled not too far from where they were cut because they are dead and there is no risk of them spreading.
  • New stalks were put into garbage bags and solarized, which is a method of cooking and killing the roots and seeds in the sun. This is because any part of the new stalk or rhizome, left behind can start a new patch of knotweed.

The tarp will be maintained and left on for at least one season. We are hopeful and excited to potentially upcycle more boat shrink wrap in the future!

Check out the HCA Insider on the process!

Update – July 6, 2021 It has been about a month of solarization so will be disposing of the bags into the garbage bin. Staff have been trampling the knotweed every week or so to stop any growth from happening underneath. So far, we haven’t had any knotweed try to break through the tarp.
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