Planning & Development

Development sites where invasive non native species are present (most commonly Japanese knotweed) require coordinated and considered action to ensure that there is no breach of relevant legislation or no threat of spread.

The following steps should be followed:

1. Early detection:

  • The presence of invasive non-native species on sites proposed for development should be identified as part of the wider ecological assessment of the site in advance of plans being finalised. If there are existing staff on site they may have skills or knowledge to inform the surveyor/assessor of the presence of any such species of concern..
  • ID material can be found here

2. Create a site plan:

  • This includes accurately mapping all species of concern present.  To make this processes easier, LISI have developed a record sheet which can be accessed here, which includes further information.
  • There are a variety of elements that need to be considered as part of any site plan. The best model is the Environment Agency’s document ‘the knotweed code of practice’.

This is of particular use if you have Japanese knotweed on your site but the principles within the document also apply to many other non-native invasive species

3. Control:

  • There are a range of different chemical and mechanical methods which can be used for treatment, further information is available here.

4. Contain:

  • Where control is not possible, or is to be completed at a later date, it is best to contain the infestation until it can be removed. If you do nothing to contain the infestation it could result in a higher cost at a later date as the species may be spread further around your site. A range of containment methods can be found in the Environment Agency’s ‘the knotweed code of practice’.

5. Keep records and monitor:

  • It is important to record where on the site Japanese knotweed has been present and then keep detailed notes on how and when it was treated. This will allow the area to be monitored and will help direct further works if needed.  Ultimately you will be able to record the “absence” of the non native invasive species on your site.  This is important as it enables others to learn from your example and enables LISI to keep track on how and where species are being eradicated.

Further information is available from:
The Knotweed Code of Practice, Environment Agency, updated July 2013
Cornwall Council
Devon County Council – Knotweed Forum
Environment Agency