Smooth Cordgrass
(Spartina alterniflora)

Description: Morphology of this species can be variable due to a combination of environmental factors and its ability to hybridize with our native cordgrass, Spartina foliosa. S. alterniflora resembles California cordgrass (S. foliosa), but a few key characteristics help in identifying this aggressive species. The leaf sheath that is below the mud surface is pink in young smooth cordgrass plants, while the native's is always white. This pink coloration is lost in older plants. The inflorescences of Spartina alterniflora have an open arrangement, but in Spartina foliosa they are arranged in a dense cylindrical orientation. In general, Spartina alterniflora is a larger plant and can be 250 cm high bearing leaves 20-55 cm long (the native S. foliosa grows up to 120 cm with leaves 45 cm).

Habitat: Occurs in mud-cobble mixes, tidal mudflats, saltmarshes, sheltered coasts, and in brackish waters.

Origin: Texas to the Gulf of St. Lawrence and Newfoundland; also native to Atlantic South America.

Invaded Areas: California, Oregon, and Washington; northwest Europe, New Zealand, and China.

Concerns: In estuaries with native cordgrass species (such as San Francisco Bay), this invader has been shown to outcompete or hybridize with the native. The invader has also spread farther down mudflats than the native, leaving smaller areas for shorebird foraging, blocking flood control channels, and hampering navigation. In Elkhorn Slough, there is no native cordgrass, so invasion by this species could dramatically alter the estuarine landscape by forming dense vegetated stands in areas previously occupied by intertidal mudflats.