Invasive Plants of California's Wildland

Dense-flowered cordgrass (Spartina densiflora) is a perennial cordgrass distinguished from the native cordgrass growing in West Coast coastal salt marshes by its grayish foliage, narrower leaf blades, dense, compact growth form (giving the plant the appearance of growing in distinct clumps), and earlier bloom period (up to a month earlier than native cordgrass).

Dense-flowered cordgrass is found along the central and northern California coast, particularly in Humboldt Bay salt marshes and Corte Madera Creek in Marin County. Eicher (1987) found it to be distributed between 5.7 and 8.4 feet MLLW(mean low low water) (or 1.7 to 2.6 meters) at Humboldt Bay.

This species was introduced in the 1800s from Chile by lumber ships that emptied their ballast water into Humboldt Bay when loading north coast lumber bound for Chile (Spicher and Josselyn 1985). Until 1984, when it was recognized as a distinct and exotic taxon, it had been misidentified as a northern form of the native Spartina foliosa. It is the dominant vegetation growing between lower and higher elevational populations of pickleweed (Salicornia sp.). It was introduced into a marsh restoration project at Creekside Park in Marin County by a landscape architect. It appears to have traveled across San Francisco Bay to Richmond, where it grows in clumps in parts of East Bay Regional Park.

Dense-flowered cordgrass grows at a slightly higher elevation than native cordgrass and thus competes and replaces native plants such as Frankenia salina, Limonium californicum, and Jaumea carnosa in the middle to high tidal zone.

Little work has been done on techniques for removal of this cordgrass, but methods used to control and eliminate Spartina alterniflora should be effective on S. densiflora.