Invasive Non-native Plant Species

Many of the river banks in the Lune catchment are being colonised by invasive non-native species such as Japanese Knotweed and Himalayan Balsam. These plants colonise river banks at the expense of our native grasses and flowers. Both of these species have been seen along the banks of the Clough River and the Parish Council is keen to stop the spread of these plants. At present the South Cumbria Rivers Trust is running a county wide initiative to map out occurrences of invasive species with the aim of controlling the spread of these plants. The Trust has a small number of Local Action Groups throughout the county who pull up Himalayan balsam and dig up American skunk cabbage. Japanese Knotweed requires treatment with herbicides but the Trust can offer advice and possibly help in eradicating this too.

The Parish Council would be interested in hearing from anyone who thinks they may have an invasive species on their land so we can inform the Trust. We would also be interested in hearing from anyone who may be interested in forming a surveying party to walk along the river banks recording any invasive species or if any local residents would be interested in forming an action party to rid the river banks of these species in the summer.

Identification of Invasive species

Japanese knotweed is the most invasive species in Britain and can grow by 10cm per day. It spreads extremely rapidly and will happily grow through concrete, tarmac and foundations. The stem has a bamboo like appearance which can reach three metres high and move up to seven metres from the plant. Japanese knotweed is extremely difficult to control without the use of pesticides and contractors who can carry out this work are often very expensive. We could try and get funding from the Lune Rivers trust or South Cumbria Rivers Trust for this work.

Himalayan Balsam is an attractive plant but it out-competes native plant species, damages habitats and when it dies back in the autumn, large areas of bare soil are left leaving banks liable to erosion. It is a brillian reproducer and is spreading fast. Himalayan Balsam can be hand pulled form late May but care needs to be taken not to tread smaller plants into the ground as they root very easily from stem nodes.

The pulled stems then need to be piled up well away from any watercourse, preferably on higher ground, where they will soon compost down. The plants then need to be repeat pulled at monthly intervals until the seeds form. Dense stands can be cut or “strimmed” at ground level several times during the growing season.

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