While “enjoying” the current summer hiatus in government and given the continuing popularity of INNSA’s Code of Practice – Managing Japanese Knotweed, we at INNSA felt it was worth a quick update on what the government does still have in place as regards invasive plant species management.

There are two principal sets of guidance we’ve reviewed – Regulatory Position Statement (RPS) 178 – which deals with the legal aspects of managing invasive species – and some under-publicised land management guidance from the EA, Defra and Natural England, one set specifically about Japanese knotweed and another on preventing the spread of invasive non-native plants.

Admittedly, the Japanese knotweed guidance hasn’t been updated since December 2021 and RPS 178 was last updated in April 2019 (even though it includes a review date of 30th June 2021!). But then, there haven’t been landmark changes in the regulatory environment recently (although, of course, RICS recently updated their own guidance and Defra’s revised National Action Plan is due any time… as it has been for many months).

There certainly haven’t been any major changes in non-native plants themselves over the last year, either – although the EA and other stakeholders continue to push the “Check-Clean-Dry” campaign to manage the spread of aquatic invasives and we continue to see reports of significant infestations of plants not covered by the Wildlife and Countryside Act schedule nine, including stag’s horn sumach (Rhus typhina) and rice paper plant (Tetrapanax papyrifer).

The key points of the government’s land management guidance should be well-known to INNSA members, but it’s potentially a good independent resource to make available to clients and members of the public or to support INNSA’s own guidance. The more general advice, however, only explicitly covers giant hogweed, Himalayan balsam, Rhododendron ponticum and New Zealand pygmyweed.

The guidance is concise and clear, focussing on duties and responsibilities rather than methodologies or best practice. It makes clear that land managers must prevent Japanese knotweed from spreading off the property while also clarifying there is no legal duty to remove it unless it’s causing a nuisance.

It also underlines that Japanese knotweed treatment programmes will require repeat applications of herbicide for at least three years and that only approved herbicides may be used and must be applied by a competent certificate holder. It also outlines the requirements of RPS178 and the regulations relating to removal of Japanese knotweed waste from site.

The more general guidance has more of a focus on Integrated Pest Management (IPM) including pulling, grubbing and seasonal pruning as well as burial and removal from site. There are caveats about composting, both in terms of effectiveness and the control of potentially hazardous wastes (due to herbicide residues). Encouragingly there is a recommendation to re-establish native species to protect soils and prevent re-infestation.

There are specific mentions for Natural England and the Environment Agency with regard to treatments on protected sites and near to watercourses and specific references to INNSA in reference to finding competent remediation contractors.

The key points of note in RPS 178 from INNSA’s standpoint are:

  • You must have a management plan for excavation and treatment of invasive plants.
  • Limits on where you can bury material (i.e. on land of low habitat value).
  • Limits on what material you can bury, including that species other than Japanese knotweed should come from aquatic, riparian (riverside) or wetland habitats.
  • Minimum depths and coverage levels for burials and a maximum limit of 1,000 tonnes of material.
  • Burying plants other than Japanese knotweed must conform to IPM norms – which require you to consider less-impactful alternatives.
  • Requirement to notify the Environment Agency at least one week before a burial.
  • Confirmation that dead Japanese knotweed canes can be composted on site if cut above 100mm above the crown.
  • A confirmation that screened (or sieved) soils must not be removed from site as “clean”.
  • Confirmation that such soils must also *not* be widely spread across the site (although they can be moved and stockpiled in specific areas).
  • Additional areas where screened soils cannot be used, including near watercourses, site boundaries and existing amenity areas.
  • There’s also a section about burning, but given the viability of this method, the alternatives and impacts, INNSA don’t generally recommend burning as a go-to method of management.

As mentioned earlier, while little has changed recently in this area, Defra’s revised National Action Plan is currently expected in October, when we’re likely to see a much stronger focus on IPM – with an effective requirement to consider IPM for all projects, and a duty to minimise herbicide application where possible.

INNSA is in consultation with Defra about how the invasive species industry can continue to lead the way in the implementation of mechanical remediation and how we can achieve integration of the NAP goals into the INNSA Standards going forward.

Chris Oliver