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Japanese Knotweed Removal

AJW Ltd: Invasive Weed Treatment Center

Japanese Knotweed control & eradicationJapanese Knotweed (JKW) is a non-native invasive species of plant which is common throughout the UK. Once a rhizome has started to establish a new stand the plant, uncontrolled, will continue to spread. In some areas, for example Cornwall, many hectares are covered in the plant where it out competes other native flora.

It is now illegal to spread or plant JKW and owners of property where it is established have a duty to stop its spread. The plant was brought to the UK by the Victorians as an ornamental plant and now has become the No 1 villain in the list of invasive species.

The plants seeds are not viable in the UK so the spread of the plant is by the movement of rhizomes (roots) and these are spread in a number of ways.

 Contaminated soil movement

One small piece of rhizome will establish a new stand when moved in contaminated soil.

Along transport corridors

Trains and traffic may take small rhizomes and move them.


Small pieces of rhizome can break off into the waterway and move down stream and establish new colonies.

The rhizomes will extend further that the extent of the visible top growth. As a guide a 7 meter radius from the visible plant should be considered contaminated.

Soil is not to be removed from JKW contaminated areas. If it is necessary to remove soil it must be treated as contaminated waste and disposed of accordingly. Before treatment starts old JKW stems must be cut down and removed, being careful that all of the rhizome and crown is left undisturbed on site. Chemical treatment, where possible, should commence as soon as the JKW has been identified.

Obviously the most cost effect method of treating JKW is with chemical.  JKW needs more than one application of herbicide to control. It may take more than one season to control. In some situations 3 or more seasons may be required to gain full control. We recommend 3-4 applications of herbicide during the growing season using a number of different chemicals and treatment techniques. Other desirable vegetation within the contaminated area may be damaged by the treatment process.

Where JKW is adjacent to water a form, WQM1, is required to be completed before chemical control can take place. And operatives must have NPTC qualification PA6AW which AJW personnel hold.

The advice from the EA is that the JKW rhizomes cannot be considered controlled until no regrowth is seen in the subsequent growing season.

The releasing of insects to control JKW has been reported in the press (bio-control) but at present these are at the trial stage and not available for commercial use.

For more information about our Japanese Knotweed Removal services, please don’t hesitate to contact us today for a free no obligation quote.