Spartina densiflora (Dense-Flowered Cordgrass) is a rhizomatous grass which forms dense masses in saline upper interitdal habitats. The plants range from 270 to 1500 mm in height. It is native to South America, where it occurs on the Atlantic and Pacific coasts. It was introduced to Humboldt Bay, California, in the mid-1800s, and later transplanted to San Francisco Bay, and inroduced to Puget Sound and Vancouver, and also to Spain and Morocco. Dry ballast ws a likely historical vector, while recent introductions may have been through cargo and wetland restoration projects. This plant is considered invasive, but since it occurs mostly in the upper intertidal,, and is less aggressive than S. alterniflora, it is considered a lower priority for removal. [The genus Spartina and this species has undergone major taxonomic changes, and the status of these is unresolved. [Some taxonomists have moved Spartina into the largely terrestral grass genus Sporobolus, and designated this specuis by a prior name montevidensis. However, many botanists and ecologists support keeping the the genus Spartina. (Bortolus and 37 authors 2019). The newly designated species name Sporobolus montevidensis is rarely used, and most publications and government documents refer to this grass as Spartina densiflora.]