Invasive Species

Invasive non-native species are defined as animals or plant species that have spread outside of their natural range and threaten native biodiversity. The Colne catchment has numerous invasive non-native species associated with the water environment such as Floating Pennywort and Signal Crayfish, which alter the biodiversity of the river system threatening native species.

The Landscape Partnership Scheme are leading an ’Invasive Species’ project to raise awareness of invasive species in the Colne Valley and provide advice to landowners and the public on effective control methods. The main focus of the project is on plant invasive species with a particular interest for Floating Pennywort, Hydrocotyle ranunculoides and Himalayan Balasm,Impatiens glandulifera, two abundant species which are detrimental to the local river systems.

Himalayan Balsam

Himalayan Balsam is a native species to the western Himalayans in North India. It was introduced to the UK in 1839 for ornamental purposes but escaped from gardens and became naturalised in Britain 1850s. It rapidly colonises the river banks and areas of damp ground at the rate of spread of 645km2 annually with seeds viable up to two years. The species is now well established across the United Kingdom and throughout Colne Valley Regional Park. The species grows in dense thickets along river banks, damp areas and wet woodlands. Each plant can produce up to 800 seeds which can be ejected up to 7m from the plant and spread along watercourses. The species dominates wet habitats suppressing the growth of native plant species and dies back in autumn leaving riverbanks bare throughout winter increasing riverbank erosion threatening our local rivers.

Invasive Species Identification and Control Guide for Himalayan Balsam

For more information about Himalayan Balsam download our Identification and Control Guides below.

Himalayan Balsam

Floating Pennywort

Floating Pennywort is a native species of North and South America. It was brought to Britain in 1980s as plant for tropical aquaria and garden ponds but escaped into the wild where it naturalised in 1990s. It spreads rapidly and is commonly found in south-east England and occasionally in north-west England and Wales. The species grows in shallow margins of slow flowing river systems and water bodies. The species is a major threat to Colne Valley rivers, the species can regrow from a single node and has a rapid growth rate, up to 20cm per day, forming dense matts of entwined vegetation, which dominate watercourses, obstruct boats, prevent angling, and outcompetes native species.

Invasive Species Identification and Control Guide for Floating Pennywort

For more information about Floating Pennywort download our Identification and Control Guides below.

Floating Pennywort