Site Code
Country: United Kingdom
Central coordinates: 55.79353002o [55o 47' 36" North], -2.21692743o [2o 13' 0" West]
Administrative region: North East (North Northumberland), Scotland Forth & Borders (Roxburghshire)
Area: 893 ha
Altitude: 5 - 338
Site Description
The River Tweed is 160 km long from its source at Tweed’s Well in Scotland to the mouth at Berwick-upon Tweed. Within the site, the English section of the Tweed flows 32 km from the national boundary at Carham Wiel to the confluence of the Whiteadder Water. A further 3 km comprises the English section of the Whiteadder Water, whilst the estuary occupies an additional 5 km.
(Natural England)
Botanical Significance
Noted for lichens and habitat interest.
The component rivers have an aquatic flora characteristic of large rivers on old red sandstone. Mosses and other lower plant species are scarce, although a rare lichen Verrucaria praetermissa is found, usually on submerged siliceous rocks, within the River Tweed. The Ranunculus beds of the lower Tweed are an internationally important habitat, species characteristic of large rivers are found here including river water-crowfoot R. fluitans and brook water-crowfoot R. penicillatus subsp. pseudofluitans. The presence of curled pondweed Potamogeton crispus, fennel pondweed P. pectinatus and perfoliate pondweed P. perfoliatus, indicate the base-rich nature of the rivers. Nationally scarce plants include the graceful pondweed P. x olivaceus and the willow-leaved pondweed P. x salicifolius, natural hybrids for which the River Tweed is one of the strongholds in Great Britain. Vegetation of the river margins include the uncommon green figwort Scrophularia umbrosa and sand leek Allium scorodoprasum found along the Lower Tweed. The river margins are dominated in places by tall emergent plants such as reed canary-grass Phalaris arundinacea. Other waterside plants include water mint Mentha aquatica, water forget-me-not Myosotis scorpioides, floating sweet-grass Glyceria fluitans, creeping yellow-cress Rorippa sylvestris, brooklime Veronica beccabunga and branched burreed Sparganium erectum, many of which are typical of base-rich rivers. The variation in mineral content of the catchment is reflected in the changing communities of aquatic plants. The plant species in the upper reaches, particularly those found higher than 200 m above sea level, are typical of base and nutrient poor upland rivers. Moss species are common on the boulders and bedrock and include Fontinalis antipyretica, Amblystegium fluviatile, Philonotis fontana, Rynchostegium riparioides and Racomitrium aciculare. Filamentous green algae are also characteristic in the open, grazed moorland landscape. Other plant species are less abundant, but occasionally water starworts Callitriche spp. and water-crowfoot species such as stream water-crowfoot Ranunculus penicillatus, occur in slacks and riffles. A diatom, Didymosphenia, found in streams on the volcanic rocks in the College Valley, produces seasonal blooms, the Cheviots is the only place within England where this phenomenon is known to occur. Along the margins of the river channels, species such as water-mint Mentha aquatica, reed canary-grass Phalaris arundinacea, floating sweet-grass Glyceria fluitans, procumbent pearlwort Sagina procumbens and blinks Montia fontana occur in places. The banks support species which are characteristic of an upland grassland environment and include purple moor grass Molinia caerulea, mat-grass Nardus stricta, rushes Juncus spp. And scrub species such as gorse Ulex europaeus, hawthorn Crateagus monogyna and willows Salix spp. Alder Alnus glutinosa woodland occurs along stretches of the riverside. In the lower reaches the aquatic plants are typical of base- and nutrient-rich lowland rivers. Mosses and other lower plant species become increasingly scarce, but higher plants such as pondweeds Potamogeton spp. and water-crowfoots Ranunculus spp. increase in abundance. Characteristic species of the larger river channels include river water-crowfoot R. fluitans and stream water-crowfoot R. penicillatus. The presence of curled and perfoliate pondweeds Potamogeton crisps and P. perfoliatus in the watercourse and branched bur-reed Sparganium erectum on the river margins, indicate the base-rich nature of the rivers. Along the banks of the lower Till, non native species such as giant hogweed, Heracleum mantegazzianum, Japanese knotweed Reynoutria japonica and Himalayan balsam Impatiens glandulifera have become established. Semi-natural woodland occurs more frequently along the banks of the lower rivers, particularly along the Rivers Breamish and Till.
(Natural England)
Management guidance notes
None
Notes
None