Japanese Knotweed Removal & Treatment Solutions, Plans & Costs

Our surveyors can formulate and advise the best method of Japanese knotweed treatment for your specific situation

Residential or Commercial Japanese Knotweed – We Have the Solution

As each site is unique, treatment starts with our qualified assessors. They will visit your property to determine the appropriate course of action for Japanese Knotweed treatment or removal in line with our management plan. This may involve one or more of the following proven Knotweed control methods:

  • Herbicide Application Program (HAP)
  • Stem injection
  • Dig & dump (landfill)
  • On-site burial
  • Cell burial
  • Root barriers (Geo textile membranes)

Which Japanese Knotweed Treatment Option is the Right one?

The right approach depends on your site conditions, urgency, and long-term plans. For example, where there is no immediate construction planned, Japanese Knotweed treatment using a Herbicide Application Program (HAP) may be the most cost-effective solution.

Some mortgage lenders will accept a property if a professional management plan and HAP are in place. For urgent cases, however, faster methods such as excavation and landfill removal may be required.

South West Knotweed have the experience and accreditation to provide all recognised methods of Japanese Knotweed removal and treatment across Devon and Cornwall.

Herbicide Treatment:

Pros

  • Cost effective
  • Treatment can be carried out in situ without risk of spreading the plant further
  • Quickly reduces the capacity of the plant to spread on/off site
  • Quickly eliminates the capacity of the plant to impact built structures
  • Easy to administer

Cons

  • Can take many years to achieve acceptable results, especially where stands are mature
  • Management plans that rely solely on herbicide treatment must include at least 2 years of monitoring after all evidence of growth has ceased
  • Herbicide treatment alone should not be recommended on sites with future development plans that involve the soil being dug and disturbed
  • Construction works cannot continue in areas still containing the plant and the risks associated with landscaping treated soils, e.g. stimulating regrowth, should be made clear to the client and mitigated for
    The use of some herbicides is restricted near waterbodies and desired vegetation
  • Some herbicides can persist in the soil
  • If soil is disturbed at a later date, regrowth can occur
  • Effective control requires expert knowledge of herbicide treatment of Japanese Knotweed
  • Soil which contains Japanese Knotweed that has been treated with herbicide is still classed as controlled waste if it enters the waste stream
  • Herbicide treatment can induce temporary dormancy

Knotweed Stockpiling:

Pros

  • Cost-effective
  • Site work can be undertaken while treatment takes place elsewhere on-site

Cons

  • Requires an area that can be left undisturbed for several years
  • Soil from a stockpile must remain on the site
  • The same cons as herbicide treatment apply in the stockpile area
  • Plant material can be accidentally spread e.g. after a change in ownership
  • The depth of the stockpiled soil must be appropriate for the future use of the soil
  • Rhizome buried deeper in a bund is less likely to express itself and may become dormant; as such, bunds should be created a shallow as is practical and should not exceed 0.5m
  • If larger bunds are created, it may be necessary to apply for planning permission

Knotweed Screening:

Pros

  • Can be cost effective but not always
  • Less material needs to be disposed of to waste facility
  • The treated soil can be re-introduced on site as fill or in soft landscaping areas
  • Where soil needs to be imported, less is required from elsewhere to fill voids created by excavation

Cons

  • All screened soil is still classed as controlled waste
  • Small fragments of Japanese Knotweed will still be present in the soil and could lead to re-infestation
  • Area where screened soils are re-used must be monitored for regrowth
  • Follow up herbicide treatment or manual removal may be required
  • Plant material can be accidently spread during movement
  • Soil type and makeup dictate if it can be screened or not

Rhizome Fragmentation and Cultivation (Including Crown Removal)

Pros

  • Increases the leaf surface area to rhizome volume ratio
  • Breaks up and aerates the soil
  • Can increase the effectiveness of herbicides under certain scenarios
  • Can improve the potential for eradication on sites where the Japanese Knotweed is persistent
  • Crown removal removes a large amount of surface and underground biomass

Cons

  • Most above ground vegetation must be cleared, even desirable plants
  • Cleared vegetation would usually need to be disposed of
  • A large area must be dug to ensure all rhizome containing soil has been included
  • Rhizome located deeper in the soil may be missed and result in regrowth
  • Soil should be compacted at the end of the treatment to help reduce the potential of deep soil rhizome regrowth
  • Crown removal can be time-consuming or impractical for large infestations and removed crown must be managed appropriately

Knotweed Burial:

Pros:

  • Does not require a set-a-side area for control
  • Work can continue immediately after burial
  • Quickly removes the Japanese Knotweed from an undesirable area

    Cons:

    • Restrictions remain on the site, e.g. in some areas deep excavation would interfere with buried material
    • The use of the area above burial site is limited
    • Typically requires a large hole to receive material, so it may not be possible if soil is shallow, or water table is high
    • The appropriate environment agency must be notified
    • Plant material can be accidently spread during movement

    Root Barrier Installation:

    Pros:

    • Can be installed to reduce the chance of horizontal and vertical rhizome spread
    • Can be used to protect structures, hard surfaces, and services
    • Work can continue immediately after installation in areas protected by membranes

      Cons:

      • Tears in the membrane or poorly sealed seams between sheets can be exploited by growing rhizome
      • Can only be installed in favourable weather conditions
      • Damp and/or wet conditions and/or work surfaces will reduce the robustness of heat welded seals
      • Surface drainage and underground water can affect installation and ponding can occur, all of which must be taken into consideration
      • Installation of root barrier is a form of control/prevention to be used in conjunction with other methodology, as it is not in itself a method of eradication

      Licensed Landfill Sites:

      Pros:

      • Quickly removes the Japanese Knotweed from an undesirable area
      • No restrictions left onsite
      • Work can continue immediately after removal
      • Fast and efficient

        Cons:

        • Relatively expensive
        • Disposal to landfill reduces valuable landfill capacity and needs haulage (which damages the environment and increases the risk of Japanese Knotweed spreading) and in the long term unsustainable. As such, disposal to landfill should only be considered as last resort when Japanese Knotweed cannot be suitably disposed of on-site

        Spraying or Stem Injection with Herbicide (Lowest Priced Treatment)

        Spraying or stem injection remains the lowest-cost form of Japanese Knotweed treatment, though it usually requires several repeat applications over multiple growing seasons. Our management plans typically run for three years of treatment plus two years of monitoring, ensuring long-term control and compliance.

        Digging & Taking to Landfill (THIS CAN BE VERY COSTLY)

        When time is a major factor, such as when a developer wants to build on a site where delays will add significant costs to the project, then spraying and mechanical Japanese knotweed removal solutions are usually the solution, for when time is a factor.

        The best method is to spray the affected area several weeks prior to mechanical removal to attempt to get herbicide into the root system.

        The area affected should be excavated to a depth of three to seven metres laterally around any stand of Knotweed, to allow for the spread of the root system.

        It is essential that all Knotweed rhizomes are removed from the site and carefully transported to an approved licensed site that will accept Knotweed. Throughout the whole process only approved licensed transport companies should travel to approved licensed landfill sites, which can provide the correct official transport notes to show disposal. Japanese Knotweed removal costs in this fashion are substantial when compared to the costs of chemical application.

        In some case Geo Membranes will be used to line the excavated area to prevent the spread of any remaining rhizomes.

        With all Japanese Knotweed work, BIO SECURITY must be applied including:

        • All equipment washed down in a designated area
        • Footwear cleaned
        • Overalls cleaned
        • Japanese Knotweed fenced off and signed (mainly public areas)
        • Pathways of spread (risk evaluated)
        • Water Courses

        Japanese Knotweed rhizomes can grow into a new plant from a piece as little as you little finger nail or 0.7 grams in weight – That’s really small!!!!!

        Even after mechanically removing the Knotweed it is advisable to continue to monitor the site and be prepared to spray for re-growth.