It only takes 0.7g of rhizome (or about the size of your little fingernail) to start an infestation of knotweed. This could be as simple as your shoe after a riverbank walk which you then tread into your garden. It is important to be vigilant and think about contaminated soil to stop it before it starts.

Identification and documentation

First step: call us! Don’t touch it or try and do anything with it until you’ve spoken to an expert.

Japanese Knotweed is distinctive in appearance: Its leaves are broad oval (shield-shaped). It flowers in the spring, producing small cream and white flowers. The raised stems give the appearance of bamboo.

Dos & Don’ts

  • DON’T damage it.
  • DON’T uproot it.
  • DON’T compost it. It only takes a small piece to grow into an infestation.
  • DO mark out and fence off the area to protect it immediately. Having a barrier will help prevent further contamination.
  • DO call in the experts.

Remediation planning and contractor selection

We deal with bona fide contractors that have been vetted and approved. With our survey you can get quotes from multiple providers and decide which one is best for you.

Our recommended contractors hold a range of relevant accreditations, licences and certificates. As well as this, we invest in staff training to ensure that every single one of our workforce delivers the best services to our clients.

To be awarded accreditation the organisation must be able to demonstrate the following:


  • Be ISO 9001 and 14001 accredited.
  • Be BASIS registered.
  • Hold Amenity Assured Accreditation.
  • Operate an appropriate H&S process.
  • Hold all relevant insurance provision.
  • Demonstrate sound financial planning.
  • Be committed to continuous investment to staff training and development ensuring they hold the right skills, certificates and capabilities at all times.
  • Ensure all works are signed off by a full or associate member of IEEM or IEMA.

Remediation Methods

Different options are available depending on the urgency of the removal. All but one of the main solutions involve excavating the plant and disposing of it in the most appropriate (yet controlled) manner.

Once the plant, its roots and any contaminated surrounding soil have been removed they can either be disposed of:

  • Offsite, at a licensed landfill.
  • Onsite, stored in a safe area for future treatment of herbicide.
  • Onsite, buried underground in a specially designed interwoven, sealed, membrane capsule.

Excavation and removal off-site (Dig and Dump)

This process involves the excavation of the soil then taking the contaminated soil off site to a licensed landfill. Remediation contractors must hold a waste carrier’s licence. The law requires excavation of up to three metres in depth and seven metres wide with backfill and stabilisation needed.

Stem Injection

Stem injection involves injecting a measured concentrate of glyphosate herbicide into each cane of the weed using equipment that is specifically designed for the treatment of Japanese knotweed. Treated canes decay within two weeks; therefore the problem can be eradicated completely with visible inspection two weeks after.

Foliar Spraying

Foliar application is useful for large areas of infested sites that are not ecologically sensitive or subject to strict treatment deadlines. Foliar spraying uses herbicides topically – the weed absorbs the herbicide through the leaves.

Root barriers

Typically used in support of other Japanese knotweed removal and treatments, a root barrier is a physical membrane that is used as a preventative measure. The barrier requires excavation at three metres to fit the root barrier and requires protection. The excavation at three metres can lead to problems with utilities.

Pros and cons of each method

Treatment Pros Cons
Stem Injection Less risky to the environment with no run off, spray drift, convection or leaching. Can be used at any point during the growing season. Fast, proven treatment within one growing season. There is a very small risk of re-infestation due to the minor possibility that the injected herbicide may fail to reach extremely deep roots – this risk can be fully eradicated with thorough investigation.
Excavation & removal off-site Dig and Dump An instant solution. Can be done in all weathers. High risk of rhizome being spread. High risk of infestation returning. Very intrusive. You risk legal action if the knotweed is not disposed of correctly. It can be costly, with additional backfill and stabilisation needed.
Foliar Spraying The easiest solution for treating large areas. It can damage other plants and wildlife. It is heavily reliant on weather conditions. Its effectiveness is determined by the number of treatments. Treatment can only take place in Autumn.
Root barriers Fast and easy. It saves on lengthy legal costs. Stops the infestation spreading to neighbouring land. The ground must be excavated to three metres. There is a risk of damaging existing pipework. Neighbouring land could still be infested.

It can take up to three years for dead Japanese knotweed stalks and stems to completely biodegrade.

Professional Bodies and Remediators

INNSA aims to improve standards within the industry and offers peace of mind and quality assurance to clients and customers.

NKS Partnership selection and assessment

We recommend only using accredited contractors who have the appropriate insurance and licenses and adhere to our stringent criteria.

You can find the list of our recommended remediation partners here .

Remediation issues and concerns (dodgy contractors)

Without the right actions, Japanese knotweed can cause catastrophic damage, both financially and legally. Thankfully, with appropriate and timely action the problem can be dealt with swiftly and effectively.

Unless you are a professional we would recommend that you do not try to deal with the problem yourself. Call an expert to come and survey the plant and assess the best course of action.

When choosing an expert, ensure that you check that they are fully accredited and insured. If the job is done incorrectly you could be left with an even bigger problem.

Warranties and Insurance

Knotweed remediation specialists need specific insurances and licenses for carrying out remediation work on Japanese knotweed:

  • Waste carrier’s licence
  • Environmental permit
  • Professional Indemnity insurance
  • Hired in Plant insurance
  • Public liability insurance

It is vital that contractors offer a warranty once the Japanese Knotweed has been remedied. The majority of mortgage lenders will stipulate a requirement for a warranty on any treated knotweed.

Long-term management of affected sites.

Finally, please remember – unless you’re paying out for a full excavation, this will inevitably require repeat treatments over time. Ask your remediation partner what their long-term strategy is.

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