Removing Invasive Plants : Japanese Knotweed

Japanese Knotweed in flower 
Japanese knotweed (Fallopia japonica) is a highly aggressive and invasive plant.  It is the closest thing that you'll find to Godzilla in the plant world.

It spreads by underground rhizomes, especially in wetland areas and along rivers. 

The plant originated in Asia and was introduced to the U.S. to control erosion on disturbed sites.

photo by Tom Heutte

And that is where our troubles began:

Japanese knotweed  can grow almost anywhere and spreads like crazy. .

Michael De Rosa
writes, "Cutting and removing standing vegetation is a beginning, but without removing the root ball completely, the plant will re-colonize the area within the same growing season. Moreover, the plant will regenerate into an entirely new plant from broken stems, leaves and root parts.

Knotweed will generate new growth from broken stems and rhizome parts. This is what makes knotweed such an insidious plant. It is able to clone itself from broken parts as well as aggressive rhizome growth."

Some people use it in salads! click here

Oh No! You cut it down and new plants regenerate form broken parts - stems, roots, leaves. Kind of like the Terminator in the movies. 

De Rosa says that he has removes knotweed in 2 ways: 

"The first is the harvesting of the standing living plant material. This is manually cut at the stem base and used as natural forage for particular herbivores at Zoo New England’s Franklin Park Zoo. (Zoo New England is the non-profit organization that manages Franklin Park Zoo in Boston and Stone Zoo in Stoneham, MA.) 

The roots are then harvested with the assistance of a machine or backhoe and either stockpiled and burned or buried at depth (e.g., greater than 10 feet) below grade and beneath a geo-textile barrier. "

Dig a giant hole

You must bury it deeper than 10 feet! Oh my. I am getting depressed. He writes about the 2nd way:

"The second option includes the harvesting of the standing living plant material and use as forage for Zoo New England’s residents, but it does not include the root removal. Oftentimes our sites are located in areas that preclude the use of heavy equipment. In these situations we will continually harvest the knotweed on a routine basis, typically every 3 to 4 weeks. 

We are continually stressing the plant and forcing it to utilize stored energy in the root system to produce more stems and leaves without getting much energy in return. These new shoots are excellent forage for the Zoo animals  and  contribute  to  their  winter  and summer supply of forage plants.

This option can also be augmented with a chemical treatment in the fall of each year when the plant is transferring energy to the root mass for storage in the winter dormancy period... Without sunlight and the ability to photosynthesize, the hypothesis is that the plant will not be able to grow and will ultimately senesce."

What chemical treatment? I don't know...probably Round Up but he doesn't want to say that word. Just a guess. 

 See more at:

 Or you can eat it! Make mass quantities of Knotweed and Ginger Jam:

Knotweed and Ginger Jam  - click here for recipe


  1. I've gotten rid of the tartarian honeysuckle, the buckthorn and am working on lily of the valley which is invading the beds. Unfortunately, I have a neighbor who lets every weed and tree grow all over his yard. If this was growing here he would be growing it.

    1. Denise, tell us your secret - is it sheer determination and strong arm muscles?

  2. Great guide here! It can be a lot of work to get rid of plants like these. Thanks for the tips on removing invasive species!

    1. Thanks Jordan..I like the idea that they feed animals.


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