Persicaria lapathifolia
Stems stout, erect, over 1 m high. Leaves lanceolate or sometimes broader, 7–15 cm long, glandular-dotted underneath. Flowers in dense spikes 2–6 cm long forming a terminal panicle, the whole ± glandular-dotted. Perianth pink. Stipular sheaths ribbed, not ciliate. Annual herb. Widespread. In or near water. Fl. summer. Pale Knotweed