Tweed Invasives Project

Clockwise from top left: giant hogweed, Himalayan balsam, American skunk cabbage, Japanese knotweed

Invasive non-native species (INNS) threaten biodiversity, ecosystems and our economy; they are one of the top five drivers of biodiversity loss globally and cost the British economy nearly £1.9 billion per year. The Tweed Invasives Project got underway in 2002, as a result of strong public demand. Initially, giant hogweed was the focus species for our control programme, with Japanese knotweed, Himalayan balsam and American skunk cabbage joining the list of key species of concern. We now operate one of the UK’s largest and most successful invasive non-native plant species control programmes, covering 5000 km² and involving many volunteers.

If you’d like more information you can read a brief history of the project, or take a look at our best-practice manual, The Tweed Invasives Project: 18 Years of Catchment-wide Control, which gives a detailed guide to delivering a long-term, catchment-scale invasive non-native plant species control programme.

Report Target Species

Help us control these damaging invasive non-native plant species by sending in your sightings. If you think you’ve seen one of the invasive species below, or need more information, please email us at info@tweedforum.org giving your name, contact number, the exact location of the species and the date seen. Please include a photo of the plant if possible.

Giant Hogweed

Easy to identify when fully grown by height, size of leaves and size of flowers. All parts of the plant contain chemicals called furanocoumarins which pose a risk to human health. When in contact with human skin and in the presence of sunlight, these chemicals cause severe burns and blistering. Giant hogweed impacts river ecosystems by out-competing native plants and leaving riverbanks prone to erosion in winter. Detailed information on how to identify giant hogweed is available from NNSS.

Find out more about how we control giant hogweed.

Japanese Knotweed

Japanese knotweed is a tall herbaceous perennial with bamboo-like stems. Capable of exceptional growth rates and can form dense ‘stands’. This species out-competes native flora and when found in urban areas can grow through concrete and building structures! The persistence of any previous year’s dead canes and distinctive rhizome (underground root-like stems) enables year-round identification. Detailed information on how to identify Japanese knotweed is available from NNSS.

Find out more about how we control Japanese knotweed.

Himalayan Balsam

Himalayan balsam is a tall, attractive, annual herb with explosive seed heads. Although easy to identify as a mature plant with its pink-purple flowers, fleshy stem and characteristic leaves – the seedlings and last year’s dead stems of this annual are more difficult to spot. Detailed information on how to identify Himalayan balsam is available from NNSS.

Find out more about how we control Himalayan balsam.

American Skunk Cabbage

American skunk cabbage produces bright yellow flowers in early spring and can reach up to 1.5 m in height. It forms dense stands, in boggy areas, which can smother native vegetation. Detailed information on how to identify American skunk cabbage is available from NNSS.

Find out more about how we control American skunk cabbage.

Project progress

If you’d like to find out more about how the Tweed Invasives Project continues to protect the Tweed catchment from harmful INNS you can read our annual project report.

Tweed Catchment Biosecurity Plan

The current Tweed Catchment Biosecurity Plan (2026-2031) sets out objectives to prevent the introduction and spread of invasive non-native species (INNS) across the terrestrial, freshwater and marine environments of the Tweed catchment, including the adjacent Eye catchment, while recognising a broader responsibility to manage non-native species where appropriate. The current Plan reflects the transition from development-focused planning in its first iteration, to the full delivery and maintenance of established INNS management systems within the Tweed catchment. Key updates include building on agreed survey and rapid response protocols; integration of GIS and citizen science tools; clear organisational roles, with Tweed Forum and Tweed Foundation leading delivery; and alignment with the North East Invasive Non-native Species Strategy.

The Tweed Invasives Project is an important component of biosecurity planning in the Tweed catchment and we share information with the Tweed Foundation, who act on reports of invasive aquatic animal species within the catchment. Please report any sightings of an invasive aquatic animal, such as American signal crayfish, to the Tweed Foundation.

Downloads

– Tweed Catchment Biosecurity Plan (Plan, 2026-2031)
– Tweed Invasives Project: Annual Project Report (2025)
– Botanical Monitoring – Control of Priority Invasive Non-Native Riparian Plants in the Tweed Catchment (2025)
– Tweed Invasives Project: 18 Years of Catchment-wide Control (Best-practice manual, 2020)
– Controlling Invasive Plants in the Tweed Catchment (Leaflet, 2016)
– Tweed Invasives Project: A photographic record of progress between 2004 and 2009 (Photo report, 2009)