1. This account presents information on all aspects of the biology of Stachys palustris (Marsh Woundwort) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history, and conservation.
2. Stachys palustris is a monoecious perennial herb, with long creeping, strong, subsurface rhizomes. It is a common native herb growing by streams, rivers, ditches, ponds, in fens, marshes and swamps, and less frequently a weed of cultivated land.
3. Although widespread throughout most of the British Isles, S. palustris is typically a plant of land–water transitional situations that are not seral and, as such, appears to be under-represented in descriptions of plant communities.
4. Stachys palustris is typically found on intermittently flooded and poorly drained soils, which are weakly acid or weakly basic and highly fertile.
5. The production of numerous subsurface rhizomes by S. palustris helps to maintain shoot population density with little recourse to seedling recruitment.
6. Stachys × ambigua, the hybrid between Stachys palustris and S. sylvatica, is most frequent in northern and western Britain.
7. Stachys palustris is particularly valuable as a nectar source for insects, especially bumblebees. It has antispasmodic, antiseptic and astringent properties; the name ‘Woundwort’ derives from its traditional use in staunching bleeding and healing wounds.