Marginal pond plant
Great willowherb
Epilobium hirsutum
A tall, native UK marginal perennial found on pond edges and marshy ground; it produces mid-pink summer flowers that attract pollinators but spreads vigorously by rhizomes and may need managing.
PLANT PROFILE
About Great willowherb
Great willowherb (Epilobium hirsutum) is a tall, clump-forming, rhizomatous perennial commonly recorded at pond margins, ditches and marshy ground. RHS and Freshwater Habitats Trust sources show it is well suited to damp, wild planting near water where roots can spread freely, and Plantlife and RHS note it as a familiar part of wetland communities. The plant bears mid-pink flowers in summer (commonly July–September) and is particularly attractive to hoverflies and other pollinators, making it a useful species for wildlife-rich pond margins.
It is an emergent/marginal species rather than a submerged “oxygenator”: it roots in wet ground and sends erect stems and flowers above the waterline. RHS describes it as very strong-growing and rhizomatous, capable of forming dense mats of roots; this vigour is an important consideration when placing it beside smaller ponds or where you do not want it to dominate. The approved sources do not provide numeric planting-depth or water-depth ranges in centimetres, so specific cm planting or water-depth advice is not available from the material used here.
Cultivation notes from RHS indicate it will grow in damp or marshy soils and tolerates full sun to partial shade. Propagation is by division (autumn or spring) or by seed (as soon as ripe, or sown in spring). In winter the above-ground foliage dies back and can be cut back at the end of the year; the perennial rootstock/rhizomes persist. Management typically involves cutting back or removing sections and dividing plants where necessary; Freshwater Habitats Trust guidance also advises considering wildlife value before removal of pond-edge vegetation. RHS lists its hardiness as H7 and records a mature height up to around 1.5–2.5 m with a spread of about 1–1.5 m.
POND SUITABILITY