JAPANESE KNOTWOOD
By Mtracy1972
United Kingdom 
Japanese Knotwood is growing in from my elderly neighbour's garden. We moved into our house a year ago. The Knotwood has obviously been there a long time. Fortunately it is not near the house. We spend time every two weeks during the growing season 'snapping off' the long shoots. I have managed to remove some roots.
I have contacted the Environmental Agency and they have been helpful but they have not given us any suggestions of how to remove it.
A systemic is apparently the wrong thing to use and care has to be given not to contaminate the surrounding area.
I would be really grateful for any help that you can give.
Regards
Michele Tracy
26 May, 2009
Answers
The best time to spray with glyphosate is just as the leaves start turning colour in the autumn, apparently this is when chemicals returning to the roots carry it down best - may take two or three years to eradicate completely. Fortunately it does not set seed so you don't have to worry about the flowers.
26 May, 2009
Ducky and Wagger have given you good advice. Anything else you need to know you will find on the website
http://projects.exeter.ac.uk/knotweed/
28 May, 2009
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Knotweed is a real problem to remove. The plant can propgate and spreadeasily from cut roots. Regular prolonged use of Glyphosphate weedkiller (which is sprayed on the foliage) over two or three years is needed to weaken and kill the plants.
Any knotweed dug up or chopped off should be allowed to dry out totally on a plastic sheet to ensure that it is completely dead before it is disposed of.
26 May, 2009