Ask a Question forum: Japanese knotweed

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Maine (Zone 4b)
Inory
Apr 29, 2018 3:03 PM CST
Hello,

I live in zone 5. Long story, I apologize, but I am basically in tears.

1.5 years ago we bought a house with a few patches of Japanese knotweed here and there. Most of it is under control (for now at least) - no large surfacing rhizomes, no large plants, they all get trimmed by hand and immediately treated with glicophyte. Except for one disaster I just discovered.

We have an area around a maple tree, about 12-15 feet in diameter, bordered with rocks. Last year a landscaper put down supposedly landscaping fabric and about 4-5 inches of topsoil. Turns out it was not really landscaping fabric but something that resembles fleece. Effectively we covered knotweed with a warm blanket and gave it some prime nutrients to overwinter. Right now half of that topsoil is riddled with very fine thin roots, and some stalks are coming up.

Extremely angry, not sure what to do now. I am thinking about lifting this fleece up, treating exposed roots, covering everything up with two layers of landscaping fabric, making sure it is all tightly sealed around the edges and seams.

To make the area somewhat attractive since it is in the middle of our small yard, I was thinking of putting down some mulch and setting up plants in containers. My questions: is this an ok plan? Could I do the two layers of landscaping fabric and then put more topsoil and plant what I had originally planned? Or will that be too risky? Am I doomed to container gardening in that area?

Thank you!
Name: Daisy I
Reno, Nv (Zone 6b)
Not all who wander are lost
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DaisyI
Apr 29, 2018 10:10 PM CST
Welcome!

I hate to be the bearer of bad news but landscape fabric is just a way to get you to spend more money. Landscape fabric encourages and protects weeds (as you just found out) and makes it impossible to pull what grows.

Get rid of the landscape fabric. Mulch won't kill Knotweed either. Its time for more weed pulling. Sighing!

But Glyphosate (I assume that's what you meant) will kill your Maple if you use too much. The other thing that will kill your maple is adding soil or mulch too close to the trunk of the tree - keep it back at least two feet. Any mulch or added soil outside that area should be only 2 or 3 inches thick.
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central Maryland
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sallyg
Apr 30, 2018 5:39 AM CST
agreed. (The tears are understandable.)


Let's hope the knotweed roots are all caught IN the fleecy stuff and most of it comes out with it.

i think you will be using herbicide on any green shoots of knotweed, until they cease. Hold cardboard behind what you are spraying so you don't get it on other things.
..come into the peace of wild things..-Wendell Berry
Life is a buffet (anon)

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