Description: When Spartina x alterniflora (an American introduction) hybridized with the native English S. maritima it produced a sterile hybrid called Spartina x townsendii . It is sterile and cannot produce seed, but is a vigorous colonizer of estuarine mudflats and was deliberately introduced into Lough Foyle by the LMS railway company to protect their coastal line to Londonderry from erosion by the sea. The Lough Foyle population seems to be the only one of this hybrid in Northern Ireland.

The derivative Spartina x anglica (Common cord-grass) occurs mixed up with the Spartina x townsendii in Lough Foyle in some places.

All names: Spartina alterniflora x maritima (S. x townsendii) Groves & J.Groves; Spartina x townsendii Groves & J.Groves; Spartina alterniflora x maritima; Spartina alternifolia x maritima

Distribution Map from NBN: Spartina alterniflora x maritima at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Spartina alterniflora x maritima at iNaturalist World Species Observations database.