Japanese Knotweed works: FAQs

1. What is the problem with Japanese Knotweed?

Knotweed is an invasive species that causes significant damage to structures and ecosystems. It outcompetes native vegetation and spreads rapidly. All landowners have a duty to manage Japanese Knotweed on their sites. Since the inception of the Paddock project, the spread of Japanese Knotweed has been observed and is now threatening some of the unique habitats.

2. What treatment has been carried out so far?

Some sensitive chemical treatment has been undertaken in selected areas at The Paddock. The recent comprehensive site remediation scheme involved capping. Capping is a process whereby Japanese Knotweed remains on site and is buried in a pit, covered over with a specialist membrane, and capped with a layer of soil. It can then be planted over with suitable shallow-rooting species, such as wildflowers. To remove Japanese Knotweed from site in the volumes required would be cost-prohibitive, involve large amounts of vehicular movements with associated air pollution and be complex due to the legal requirements for disposal of this species.

 3. Why have some areas of scrub and trees been cut down?

In order to create legally-compliant capping over the Japanese Knotweed, it is imperative that no viable root systems remain in the ground that can grow and damage the membrane.  Unfortunately, large tree roots would break through the membrane and cause the Japanese Knotweed to spread. 

 4. Have you considered other options?

 Yes, spraying with glyphosate was considered. However, several factors made it an unviable option:

• Haringey Council is adopting a minimal-spraying policy in its Parks and Greenspaces Strategy.
• The expected increase in visitors with children and pets means there would be an increased risk, especially to dogs, due to the percentage cover of Japanese Knotweed in The Paddock and the volume of glyphosate required.
• Some areas of The Paddock had started to show resistance to glyphosate.
• Given the volume of Japanese Knotweed in The Paddock and the variety of ground conditions, alternative chemical remediation methods could take several years with no guarantee of effectiveness.

5. Why are some small areas being treated with glyphosate?

Japanese Knotweed has very extensive underground rhizomes (root systems) that mean a large area of surrounding habitat is damaged when it is being excavated. Working with our specialist contractors, we have identified areas where we believe controlled spraying would outweigh the potential loss of existing habitat from excavation. If you see small patches of remaining Japanese knotweed on site this is normal with this scale of works and will decline and eventually be eradicated over time, as part of the spraying programme.

6. What happened to the scrub and trees that were removed?

Felled trees were either cut into logs or large pieces for ecological uses around the site; chipped and retained on site for future use; or chipped and taken off site for use as biomass fuel.  By keeping logs stored on site, over time the rotting wood will create homes for invertebrates and fungi and allow the carbon to be stored on site.

7. What soil was used on top of the capped area?

The soil was locally-sourced from a supplier near Markfield Park and fully certified for use in The Paddock for the intended purpose. By using local suppliers we are contributing to the local economy, reducing emissions, and lowering the carbon footprint of the construction operations.

8. Why are some areas of the site fenced off?

The area designated for capping has now been sown with wildflower meadow seeds. In order to allow this time to establish it is essential to prevent footfall and trampling. Other sections are fenced off for safety purposes, e.g. around the new pond and areas that have excavations and boggy ground after the works. These areas will change over time, and we will decide in future how to amend access.

9. How will the Japanese Knotweed be managed in the future?

We have an extensive guarantee covering materials and works, and additionally a maintenance programme to ensure other parts of the sites are dealt with if needed.

10. How long will the main physical improvement works take?

The main works to improve the paths, entrance areas, signage and interpretation, wildlife-viewing hide and landscaping are due to start in Autumn 2023, and take approximately 18 months to complete. The proposed new visitor centre building will be dependent on future funding and completed later. 

11. Where can I find out more about the works?

Information about The Paddock's wider improvement plan, including the Japanese Knotweed removal can be found on Haringey Council's website: https://thepaddock.commonplace.is/ 

12. What is TCV’s role at The Paddock?

The Conservation Volunteers (TCV) are a long-standing conservation management partner for the Council, including managing Railway Fields on Green Lanes. They were appointed in 2020 as the Council’s site management partner for The Paddock. Their role is to undertake outreach and community engagement programmes, and work with The Friends of The Paddock to develop a volunteering programme to manage and improve site over time.

13. Can I get involved in The Paddock?

Yes, TCV run regular volunteering activities on Wednesdays and Fridays, as well as monthly Saturday events. Please visit The Conservation Volunteers website https://tcv.org.uk/thepaddock or contact Anna or Izzy at thepaddock@tcv.org.uk