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Upper Witham Invasive Plant Species Project

Lincolnshire Rivers Trust are working on the Upper Witham Invasive Plant Species Project, a partnership project between Lincolnshire Rivers Trust, Local Angling Clubs and RiverCare with support from the Environment Agency. 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).

Himalayan balsam (Impatiens glandulifera)

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 aesthetic appealing and occasionally it is still deliberately planted.

What some people fail to realise is that Himalayan Balsam is:

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

Japanese knotweed (Fallopia japonica)

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.

Japanese Knotweed facts:

  • Non-native and invasive, out-competing native species
  • Widespread in the UK, especially along urban rivers
  • Spreads easily, especially along rivers where roots can become snapped and transported downstream during flood events and as a result become established
  • This species can limit access for anglers and other recreational activities if left unmanaged
  • Roots can cause structural damage to paving, tarmac, buildings and flood defence structures
  • And like Himalayan balsam it can Increases erosion when the bare ground is exposed in the winter months

Giant hogweed (Heracleum mantegazzianum)

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 the UK, especially in lowland areas
  • Grows up to seven metres in height and each plant can produce between 10,000 and 50,000 seeds, which enables the plant to spread rapidly along watercourses
  • The plant produces phytotoxic sap which can cause skin burns if it comes in contact with your skin

Summary of work done May-August 2016

After obtaining land owner permission Lincolnshire Rivers Trust carried out walkover surveys along the upper Witham and its tributaries to establish areas where the three invasive plants were located. From June to August 2016, Lincolnshire Rivers Trust worked with contractors and volunteers to tackle plant species from the most upstream point of where the invasive plants were located working logically downstream. Method of removal for Himalayan balsam included hand pulling events with volunteers, chemical spraying and strimming by contractors. Chemical spraying was also carried out by contractors of giant hogweed and Japanese knotweed.

Future work

Outputs to include; 2016 report, action plan for 2017 and distribution maps of surveyed areas.

Lincolnshire Rivers Trust and partners will continue to engage with locals and parish councils to increase awareness and involvement.

Invasive species information provided by GB Non-native Species www.nonnativespecies.org

Thank you to the Environment Agency and Persimmons for the funding and we would like to kindly acknowledge contractors involved in the project Lions Grasscare and The Cawleys.

 

Details:

Lincolnshire Rivers Trust
Registered in England
Registered Charity No: 1157922

lincsrivers@gmail.com

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