Invasive Plant Management

Japanese Knotweed (Fallopia japonica) Control at Harefield Hospital, Uxbridge, Middlesex

OHES managed the control of Japanese knotweed on behalf of the Royal Brompton and Harefield foundation NHS Trust. The project involved the treatment of large stands of Japanese knotweed to prevent damage and undermining of the infrastructure of a historic building within the hospital grounds. OHES is implementing a treatment plan which will control and eradicate this invasive plant and protect this historically important part of the hospital.

Japanese Knotweed (Fallopia japonica) Control at Sharpness Dock, Gloucestershire

The site at Sharpness Docks is scheduled for major development for a renewable energy supply. OHES were commissioned to manage and control the Japanese Knotweed stand identified on site by a phase 1 habitat survey. The stand of Japanese knotweed was approximately 45sq.m. in size and was successfully managed by a combination of techniques including, stem injection and sprayer application of herbicide.

Floating Pennywort (Hydrocotyle ranunculoides) Control, Bedfont, Middlesex

Floating pennywort is one of the most invasive of non-native invasive aquatic species. The plant grows at an extraordinary rate and can smother watercourse and stillwaters once established, within a single growing season. Regular and continued management of this plant using herbicide allowed the plant to be controlled during the growing season. Continued applications of treatment will eventually control and eradicate this plant from the site.

GIS Mapping of Non-native Species, London

As part of an Environmental Risk Assessment for a site in London, OHES completed a full site survey of a 145 hectare area of land. Part of the assessment was the need to identify and map all the species present on site that were listed as ‘Species of Concern’ by the London Invasive Species Initiative(LISI) who have a number of programmes for the management and control of non-native species within London.

Each stand or individual plant was mapped on a GIS computer aided plans and areas were quantified to allow a management proposal to be formulated to feed into a strategic site management plan, to help eradicate and control the spread of the non-native invasive plant species found.

Japanese knotweed (Fallopia japonica) Eradication Programme in Residential Garden in Norfolk

OHES were commissioned to by the property owner to help eradicated Japanese knotweed from a property in Norfolk. The Japanese knotweed had become well established in a part of the garden, which allowed a stand of over 50sq.m. to develop. OHES produced a bespoke eradication programme which has successfully removed the plant, and subsequent inspections show no re-growth.

Control of Bullrush (Schoenoplectus lacustris) on the St.Patrick Stream, near Reading, Berkshire

OHES were commissioned by a local angling club who owned a section of the St.Patricks stream near to Reading; a well renowned barbel fishery feeding directly from the River Thames, to help control the steady progression of Bullrush (Schoenoplectus lacustris) into the Stream. The plant was not only creating difficulties for angling access, but was also causing excessive erosion of the opposite bank. This was particularly important as this section of bank supported a bridge abutment. The narrowing of the channel increased the potential rate of erosion against the bank, particularly during high flows, created scour and deposition. By sympathetically managing the weed, under Environment Agency consent, OHES helped to improve the section of river for angling access and helped control the erosion of the opposite bank

Case Study: Fringe Water-lily (Nymphoides peltata) Control, River Colne, Hertfordshire

We were engaged to control fringe water-lily on the River Colne, Hertfordshire. The lily was impacting river flow and access for angling, causing increased siltation and shading the river bed preventing the growth of native submerged plants.

OHES were asked to assess and deploy an improvement plan to deal with this plant. An initial chemical control was used as a primary control, which within weeks restored the river channel to open water and improve the angling access. This was followed by further physical control adjustments by the Environment Agency, which included the removal of an impounding structure to restore normal flow conditions, which made conditions less suitable for lily growth.

The combination of the initial treatment and weir adjustment helped restore the section of river, allowing it to flow freely and clearing the choking silts and weed, which vastly improved the site's visual appearance, and opened new opportunities for angling and wildlife.