Spartina : a genus of marsh grasses commonly known as cordgrass
Spartina alterniflora (Saltmarsh Cordgrass), native to the East Coast, can live in shallow water, where its roots trap sediment and help to stabilize the marsh. It prefers brackish environments. Other varieties thrive in drier environments.
In disturbed marshes or fresher waters, an invasive species, Phragmites (the common reed), can displace Spartina.