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Several weeks ago your column dealt with invasive seedlings and you recommended a vinegar solution. I have invasive bamboo that is creeping over from a neighboring property. I've tried digging it out, burning with a blow torch and (last resort) Roundup. Nothing works. Will the vinegar solution work if I do it at this time of year? Judy


Japanese Knotweed Hi Judy,
Thank you for your question. I'm assuming that you are dealing with Japanese Knotweed, which is often referred to as bamboo. In my previous answer, I should have been more specific. Basically, when you are dealing with Knotweed, you will need to inject a vinegar mixture into each knotweed stem (a very time-consuming, but 90% effective process). You need to use Horticulture Vinegar Herbicide-20% acetic acid (not cooking vinegar). This is a broad-spectrum, natural, nontoxic herbicide. You can find it in a number of places, locally and on-line including Walmart and Home Depot.

The recipe for the vinegar solution is:

- 1 gallon of Horticulture Vinegar
- 1 quart of Avenger - it's an organic weed killer that is made from lemon, lime and orange peels which also contains acetic acid. It is available locally and online (Sprigs & Twigs sells it as well)
- 1 cup of table salt
- 1 TBSP of Dawn dishwashing liquid

The usual procedure is to cut the Japanese Knotweed to about 2-3ft tall and inject the vinegar solution into the stem in the beginning to middle of October; it's too late to do it this year. About one teaspoon of this mixture should be injected into each stem of knotweed above the 1st or 2nd node from the ground using a special injection tool. The tool is necessary because Japanese Knotweed's stem is compartmentalized into sections and is covered with a waxy coating. There are several injection tools on the market; one of the best known is the JK Injection Tool - it's like a huge hypodermic needle on the end of a trigger handle (~$200.00).

As an alternative approach, I had very good luck this past spring with pulling out the knotweed. The new knotweed was about 3-4' tall when I pulled it out (late April-late May). The roots (rhizomes) came out with the stems and I just kept pulling. I was very surprised it did not come back. So that's what I will do this coming spring in the other areas on my property. Some of the rhizomes will undoubtedly remain in the soil, but I am hopeful, over-time I can win the war of attrition. This way is a lot less expensive, faster and less dangerous than injecting. Keep me posted on how you make out.

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About Linda Lillie

Linda K. Lillie is the President of Sprigs & Twigs, Inc, the premier landscape design and maintenance, tree care, lawn care, stonework, and carpentry service provider in southeastern Connecticut since 1997. She is a graduate of Connecticut College in Botany, a Connecticut Master Gardener and a national award winning landscape designer for her landscape design and landscape installation work.


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