How to get rid of Japanese Knotweed? - Ask Extension
Hi there. We are having a Japanese Knotweed invasion. We heard about pulling it out by the roots, and we are doing that but it keeps growing back. ...
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How to get rid of Japanese Knotweed? #871589
Asked June 04, 2024, 5:26 PM EDT
Hi there. We are having a Japanese Knotweed invasion. We heard about pulling it out by the roots, and we are doing that but it keeps growing back. We also heard about covering it with black plastic, but that that takes years. Is there a native species we should plant that will contest it? Or is there a way to poison it without potentially killing everything that would grow in the future in the same area?
Dutchess County New York
Expert Response
Hope this helps.
Let us know if you need any other information
Karen Ranucci
Thank you so much, Karen! What wonderful information~so helpful to us! You mentioned when we spoke that your syringe had broken in process. Do you remember if it was the very expensive syringe by JK Injection tools? Would you have any further advice on syringes? Thank you.
Best wishes,
Alisza
It is true that I did not use a very strong syringe. In the fall when the plant is retreating rather than sending its energy upwards. The knotweed has sections like bamboo. Cut below just under the ring which will leave like a little tube with a hollow in the middle before it gets to the next ring down. If you spray roundup into that eventually the plant should suck it down into its roots. Mine broke when I tried to shoot the syringe into the hard ring of the plant.
I am also attaching a PDF from Penn State that has other suggestions for eradicating knotweed.
Good luck,
Karen
Thank you Karen!
This is all fantastic information!
You've been so thorough and wonderful in your commitment to our problem~ Thank you! Thank you! Thank you!
Best wishes and Happy Gardening,
Alisza
