West Carmarthenshire · High pressure
Carmarthen, the Tywi & the Taf Estuary
The Tywi is one of the great balsam rivers of Wales — seed floats miles downstream each summer — and knotweed lines the town's riverbanks and old rail land. Covered by Carmarthenshire County Council on council land.
Streets and places to watch
- Carmarthen
- Ferryside
- Llansteffan
- St Clears
- Laugharne
- Pendine
- Whitland
- River Tywi
These are the corridors where growth is most often recorded — lane walls, verges, brook banks and cleared plots. Individual gardens are not listed.
Towns, villages and places in this area
Each place has its own local guide with a map, area facts and the plants to watch for.
What grows here
Himalayan balsam
The pink-flowered annual that lines almost every stream in Swansea. One plant throws up to 2,500 seeds and the seed floats, so a single upstream patch reseeds miles of bank.
Germinates March, flowers June–October, dies back with first frost
Japanese knotweed
Swansea is one of the worst-affected places in Britain. Knotweed dominates back lanes, railway embankments, riverbanks and derelict plots across the city, and it is the weed most likely to affect a mortgage or a sale.
Shoots March–April, peak growth June–August, canes die back brown in winter
Giant hogweed
The one that hurts people. Its sap makes skin blister badly in sunlight, and the burns can recur for years. Children are most often affected because the hollow stems look like play material.
Growth from April, flowers June–July, seeds August