Pembrokeshire · Moderate pressure

Haverfordwest, Tenby & the Pembrokeshire Coast

The Cleddau rivers carry balsam and knotweed through Haverfordwest, while the coast path and National Park grasslands face garden escapes like cotoneaster and montbretia. Covered by Pembrokeshire County Council; much of the coast is National Park land.

Streets and places to watch

Haverfordwest
Narberth
Tenby
Pembroke
Milford Haven
St Davids
Fishguard
Newport
Western Cleddau

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

Wall cotoneaster

Birds carry the berries from gardens straight onto Gower's limestone cliffs and grasslands, where cotoneaster smothers some of the rarest plant communities in Wales.

Flowers May–June, red berries autumn into winter