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Lincolnshire Rivers Trust


Welcome to the Lincolnshire Rivers Trust's invasive species interactive map.

Lincolnshire Rivers Trust are the only charity working to improve rivers across Lincolnshire. We undertake habitat projects, ensuring that species such as brown trout and water vole have returned to our rivers. Our work with schools and local communities engages people with waterlife and helping them to understand why healthy rivers are so important.

Our invasive species project is an important part of our work on the Upper Witham to improve the river for wildlife and the community alongside it.

Upper Witham Invasive Plant Species Project


The spread of invasive non-native plant species along the River Witham and its tributaries threatens the future survival of our native wild plants and animals. The Upper Witham Invasive Plant Species Project aims to remove problem plant species from the upper Witham.

We are targeting three key plants; Himalayan balsam (Impatiens glandulifera), Japanese knotweed (Fallopia japonica) and giant hogweed (Heracleum mantegazzianum). This project has been made possible with support from the Environment Agency.

We have been able to build relationships with the landowners over the course of the project so far and this has resulted in, in some cases, the understanding of responsibility to treat invasive species when a riparian (riverside) owner.

A small campaign was also launched in 2018 using social media and targeting the Parish Councils along the River Witham to educate people about the 'Tresspassers on our banks!' and what to do about them.

About the map


The map shows where we have surveyed and the type of work undertaken to remove the invasive plants (strim, pull, spray). We have also started to highlight sections where we have had significant success and/or public engagement.

Click here for tips on using the map.

Himalayan Balsam


​This pretty purplish-pink to white flowering plant was introduced as a garden plant in the early 19th century and first recorded in the wild in 1855. The general public find Himalayan Balsam aesthetically appealing and occasionally it is still deliberately planted.

  • Non-native and invasive, out-competing native species
  • Widespread in UK, especially along urban rivers
  • Spreads easily, by small seeds carried by wind or water
  • Increases likelihood of flooding during periods of high flow, due to growing in dense stands along river banks
  • As it dies back in winter, banks left bare and exposed to erosion, increasing sedimentation issues in the catchment

Himalayan Balsam Density (2016)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Himalayan Balsam Density (2017/18)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Japanese Knotweed


This plant was originally from Japan and was considered to be a rare species. It was first introduced as an ornamental plant in parks and garden and was first recorded in GB in 1886.

  • Non-native and invasive, out-competing native species
  • Widespread in UK, especially along urban rivers
  • Spreads easily, especially along rivers where roots get snapped and transported downstream during flood events
  • Limits access for anglers and other recreational activities if left unmanaged
  • Roots can cause structural damage to paving, tarmac, buildings and flood defence structures
  • Like Himalayan balsam, can increase erosion when bare ground is exposed in winter months

Japanese Knotweed Density (2016)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Japanese Knotweed Density (2017/18)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Giant Hogweed


Native to Caucasia and Central Asia, giant hogweed was introduced in Britain as an ornamental plant in the 19th century, first recorded in 1828 and closely resembles our native species Cow Parsley (Heracleum sphondylium).

  • Non-native and invasive, out-competing native species
  • Widespread in UK, especially in lowland areas
  • Grows up to 7m in height and each plant produces between 10,000 and 50,000 seeds,enabling it to spread rapidly along watercourses
  • Produces phytotoxic sap which can cause skin burns if it comes in contact with your skin

Giant Hogweed Density (2016)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Giant Hogweed Density (2017/18)


Almost continuous cover
>3m2 but not necessarily continuous
~1m2 - 3m2 (distinct patches)
~1m2 (patches becoming more distinct along the bank)
No distict patches and/or a few scattered plants

Stoke Rochford (Cringle Brook)


The uppermost location for Himalayan balsam and Japanese knotweed in the catchment. This was treated successfully.

(Himalayan balsam)

Cringle Brook

Barkston


This section is still proving troublesome to treat, with strong growth in 2018 on the surrounding floodplain. We have volunteer support here from our friends at GAAFFS (Grantham Angling Association Fly Fishing Section).

(Himalayan balsam)

Belton


This section is owned by the National Trust. We originally had a volunteer day here with Anglian Water at the start of the project. The National Trust and their volunteers and contractors and now managing this section with spraying and pulling.

(Giant hogweed)

Persimmon Sump


This section is in the middle of a relatively new housing estate. The change here has been remarkable and we are now able to access the beck to take school groups.

(Himalayan balsam)

Grantham


We have worked with the local Rivercare group here. This section goes through two adajent parks - Wyndham and Queen Elizabeth - and has great local involvement and community action.

(Himalayan balsam)

Manthorpe Mill


The landowner here has really engaged with the projects and we have been able to educate the gardeners on why the invasive plants are an issue for the river. They are now taking full responsibility for the removal on their section.

(Himalayan balsam)

Long Bennington


An engaged Parish Council and local community has enabled us to dramatically reduce the Himalayan Balsam on this section.

(Himalayan balsam)


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