Tweed Invasives Project

We’ve been tackling invasive plant species in and around the River Tweed and its tributaries since 2002, when Giant Hogweed was identified as one of the biggest threats to the River. Giant Hogweed overwhelms our native flora, causes river bank erosion (which increases flood risk) and, if touched, can cause painful skin blistering. Japanese Knotweed, Himalayan Balsam and American Skunk Cabbage have since been added to the list of invasive plant species that threaten our ecosystems. We now operate one of the UK’s largest and most successful invasive plant control programmes.

If you’d like more information you can read a brief history of the project, or the more in-depth Tweed Invasives Project: A Case Study.

Target Species

If you think you’ve seen one of the invasive species below, or need more information, please email us on giving your name, contact number, the exact location of the species and the date seen.  If you can email us a photo of the plant from your smartphone or camera that would help too.

Giant Hogweed

Easy to identify when fully grown by height, size of leaves and size of flowers. Can be confused with native hogweed when not fully grown or when growth is stunted (e.g. regrowth after cutting). Contact with any part of this plant must be avoided as even minute amounts of sap can cause blistering of the skin following exposure to sunlight. Read more…

Japanese Knotweed

Tall herbaceous perennial with bamboo like stems. Often grows into dense thickets. Characteristic leaves and stems, persistence of last year’s dead canes and distinctive rhizome (underground root-like stems) enables year-round identification. Read more…

Himalayan Balsam

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. Read more…

Giant hogweed
Giant Hogweed
Japanese Knotweed
Himalayan Balsam


Find out more about how we are tackling the following species: Giant Hogweed, Japanese Knotweed, American Skunk Cabbage and Himalayan Balsam.

Find out more about how the project is progressing.


The Tweed Invasives Project is an integral part of the Tweed Catchment Bio-Security Planning Initiative (you can download the plan below). As part of our biosecurity planning we share information with the Tweed Foundation, who act on reports of invasive aquatic animal species within the catchment. You can report a sighting of an invasive aquatic animal, such as American signal crayfish, to the Foundation using this link


Tweed Catchment Bio-Security Plan (Plan, 2011-2016)
Controlling Invasive Plants in the Tweed Catchment (Leaflet, 2014)
Tweed Invasives Project: Summary Report (2018)
Assessment of Impact of Long Term Control of Invasive Non-native Riparian Plants in the Tweed Catchment and Restoration of Native Biodiversity (Report, 2013)
Tweed Invasives Project: A photographic record of progress between 2004 and 2009 (Photo Report, 2009)
The Tweed Invasives Project: The long-term control of Giant Hogweed and Japanese Knotweed; a case study of the Tweed and practical steps to establishing and delivering a successful, long-term control strategy (Report, 2006)

Other useful links