Successful Control or Eradication of Japanese Knotweed

The last few months have seen some interesting news and events regarding Japanese knotweed.

April 2018, the University of Swansea published data concluding that Japanese knotweed cannot be eradicated using herbicide alone. June 2018, Network Rail lost their high court appeal against a judgment for causing a private nuisance by allowing knotweed on their land to affect neighbouring properties. It creates a landmark legal precedent and ‘case law’ for the control of Japanese knotweed.

July 2018, the University of Leeds published a report that found no evidence that Japanese knotweed causes significant structural damage. Co-author Dr Karen Bacon stated, “Japanese knotweed is capable of damaging built structures, but where this occurs, it is usually because an existing weakness or defect has been exacerbated.”

So what does this all mean for property owners, designers, architects and developers?

  1. Beware of contractors offering quick fixes and eradication solutions resulting from herbicide treatment alone.
  2. If you have allowed underground knotweed rhizome to encroach into a neighbouring property you can be sued by the affect property owner.
  3. The presence of knotweed rhizome in the soils imposed a financial and amenity burden on the land owner and interferes with the land’s amenity value. It is not merely due to the risk of potential physical damage, but more importantly the difficulty in using, landscaping and developing the property in the future.

What should be done for property refurbs or builds affected by Japanese knotweed?

It is advised that a knotweed specialist contractor from an industry trade body such as the Property Care Association (PCA) is involved on the project. A specialist contractor will conduct a full survey of the property providing a Knotweed Management Plan (KMP) including; the survey, survey drawing, RICS property risk category and remedial proposals. They can also ultimately provide Insurance Backed Guarantees (IBG) on their work, which are normally required by mortgage providers if the property is being sold.

Japanese Knotweed Ltd is a PCA approved contractor and undertakes all aspects of knotweed surveying, legal reporting, treatment and removal. They advise that a 10 year KMP offering herbicide treatment with an IBG is suitable in most domestic situations. Where there are plans to disturb rhizome contaminated ground (at home or on development sites), or it’s simply undesirable to have long term herbicide treatments (and a resulting no-disturbance zone) on the property, they recommend excavation and removal of the knotweed.

Excavation projects are most successful where the knotweed contractor works with the designer, architect or developer to devise a remedial solution in-line with the development plan. Early engagement will ultimately save the client time and money.

Japanese knotweed is not to be ignored!