River Tweed IPA
Location: 2 miles west of Berwick-upon-Tweed, through Whiteadder Water, into the Lammermuir Hills.
Grid Reference: NT 864 556
Rising at Tweed's Well, near the Lanarkshire boundary, the Tweed flows east to join the North Sea at Berwick upon Tweed, for the final four miles of its journey running entirely through England. The lower reaches of the Tweed and Whiteadder are nationally important examples of lowland rivers with minimal gradients in England. The site is of international importance for its estuary, intertidal mud and sandflats and its floating and aquatic plant communities, but has principally been selected as an IPA due to its rare lichen population of the River jelly lichen Collema dichotomum.
Plants you could see
The river has a high ecological diversity which reflects the mixed geology of its catchment area. The Ranunculus beds of the lower Tweed are an internationally important habitat and species characteristic of large rivers are found here. Stream water-crowfoot, a species of southern rivers and streams, occurs at its most northerly location, as does fan-leaved water-crowfoot, along with river water-crowfoot, common water-crowfoot, pond water-crowfoot and a range of hybrids. The Tweed is also the most northerly site for flowering-rush.
Nationally scarce plants to be found here include the graceful pondweed and the willow-leaved pondweed, natural hybrids for which the River Tweed is one of the strongholds in Great Britain. Other pondweeds which occur are curled pondweed, fennel pondweed and perfoliate pondweed.
Vegetation of the river margins includes the uncommon green figwort and sand leek, found along the Lower Tweed. In places the margins are dominated by tall emergent plants such as reed canary-grass. Other waterside plants include water-mint, water forget-me-not, floating sweet-grass, creeping yellow-cress, brooklime and branched bur-reed.
River jelly lichen is an aquatic lichen which grows on submerged rocks in intermediate and upland fast-flowing streams. It is now rare and protected in the UK, but the River Tweed is one of the sites on which it can still be found.