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Japanese Knotweed Management

When it comes to managing Japanese Knotweed, whether it is on a commercial site or within a residential garden, there is no‘one solution fits all’. Each stand of Japanese knotweed needs careful consideration, From the initial japanese knotweed inspection to the appropriate choice of control strategy to the consideration of options for waste control.

If you are a construction, landscaper/gardener or a property related professional, to help guide you through some of these considerations, we have below a series of support pages to help you.

However, if you are looking for qualified, experienced and professional help to manage your Japanese Knotweed problems, you can easily find a local PCA specialist happy to assist.

Find local specialists >>

1st step in management - Japanese Knotweed Inspection

The initial inspection of Japanese knotweed is a critical step when considering its management and control. We strongly recommend contacting one of our invasive weed members to help with this.  But what exactly should you expect from a Japanese knotweed site inspection and how does this impact the overall management of the plant?

To understand more, visit our Japanese Knotweed Inspections page.

Japanese knotweed inspection >>

Professional treatment options to manage Knotweed

There are many ways to manage Japanese Knotweed, ranging from long-term management through the use of herbicide sprays (usually for a minimum of three years) to faster, but more disruptive full-scale excavations using plant machinery.

Management by herbicide spray

For many, particularly residential sites,  a control program and subsequent management plan using herbicide spray is the most common and cost effective approach which causes the least disruptive method for Japanese knotweed management. 

However, Japanese knotweed rhizomes (in the soil) may not be entirely ‘killed off’ (eradicated) by such a programme and there remains a residual risk of re-growth (when herbicide-induced dormancy starts to weaken).  This risk can be off-set by the issue of Guarantees and these, when backed-up by appropriate insurance, are acceptable to most mortgage lenders. The risk of re-growth after ‘Completion’ of a herbicide management plan is greatly increased if the ground is disturbed by digging, so in practise such guarantees preclude any development work or landscaping in the affected area.

For professionals wanting to better understand the limitations, restrictions, and safety considerations regarding herbicide spray programmes, click on the buttons below. 

Using professional herbicides >>

Training: Safe use of herbicides >>

Management through excavation & burial

Another approach to Japanese knotweed management is to remove the plant and its extensive root/rhizome network from the soil completely*.  The key advantages of this approach are its speed and the fact that, once completed, the site is suitable for development.  

But excavation works can be extensive (Japanese knotweed rhizomes can spread many meters in all directions) therefore generating large volumes of waste soils which require further processing or disposal, all adding-up to greater costs not to mention the disruption.  

This approach is most common on commercial sites for obvious reasons, but is increasingly offered in domestic residential settings too (to enable extension works to start or the laying of new driveway etc.). 

For further details regarding Excavation and Disposal of Japanese knotweed, click on the button below.

Knotweed Excavation & Burial Page >>

Combining management solutions

It is worth noting that the Japanese Knotweed management options above are not entirely exclusive to each other.  For example, before excavation the above ground part of the plants would normally be treated with herbicide (ideally more than once) and, vice versa. Many herbicide management plans might include a certain degree of digging to disturb and/or remove rhizomes from the upper layers of soil (e.g. to optimise post-completion amenity use of the area). 

Japanese knotweed - waste management

Japanese knotweed wastes arising from management activities will almost always be defined as ‘Controlled waste’ under the Environmental Protection Act 1990 and must therefore be handled and processed in accordance with the Environmental Protection (Duty of Care) Regulations 1991. This classification arises out of the fact that even tiny parts of the plant, especially rhizome fragments, can easily give rise to new plants wherever the waste is deposited, whether deliberately or accidentally.  Separate regulations apply if the soil etc. is also deemed to be Hazardous but this normally only arises on post-industrial sites.  

Waste Control - Stopping the spread >>

Useful CPD videos on Japanese knotweed (& other invasive weeds)

Technical documents you can view

For those interested, there is a variety of invasive weed related 'Codes of Practice', Technical Documents, Guidance Notes and other related documents via our 'Invasive Weed Control Document Library'.  Simply click on the button below to view the library.  Documents of interest include:

  • NEW – Herbicide Treatments and Japanese knotweed – PCA Guidance Note
  • Restrictions on the Use of Herbicides on Hard Surfaces
  • Root Barrier and Japanese Knotweed Remediation
  • Waste Classification for Works in a Commercial Setting
  • UPDATED – List of Invasive Non-Native Plant Species

Visit the document library >>

More to it than expected? Find a qualified Japanese Knotweed specialist

As we mentioned at the start, there is a lot more to the management and control of Japanese Knotweed than most professionals expect.  There are critical considerations to take into account at every stage that will impact costs and time depending on what is the most appropriate method to control and manage the Knotweed issue.

PCA qualified Japanese Knotweed specialists can assist you.  To find PCA contractor members able to conduct site investigations and consultancy towards management and control, simply use the search functionality below to find qualified specialists near you.

Find a local specialist >>

Want to learn more about Japanese knotweed?

For those interested in learning more about Japanese knotweed, there is a variety of PCA training options for surveying professionals as well as technical/trade professionals. 

Use the search tool below to find available Japanese knotweed and other invasive weed related training courses or simply go to our training & qualifications section.  Alternatively, if you want to chat to someone, contract our training team on 01480 400 000 or contact them online.

More about training >>

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Invasive weed management

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