Scientific name: Spartina alterniflora

What Is It?

Spartina species are aquatic grasses that grow on the mudflats and marshes of Puget Sound and coastal estuaries. The plants tend to grow in circular clumps called ‘clones’ and are bright green in color. Smooth cordgrass came to Washington in the late 1800s, either in shipments of oysters from the East Coast or as packing material in ships’ cargo. It since has spread, vigorously colonizing intertidal saltwater areas as well as the perimeters of freshwater areas. This grass out competes native plant species, including rare and endangered plant species, reducing marsh biodiversity and ecology functions.

Is It Here Yet?

Yes. Cordgrass is in parts in Puget Sound, Grays Harbor, and Willapa Bay. It also has been reported in Jefferson, Kitsap, and Mason Counties, and small populations were recently located near the mouth of the Columbia River.

Why Should I Care?

Rhizomes, a type of underground stem, spread outwards from a cordgrass plant in all directions. New plants can grow from the outstretched rhizomes, eventually forming large patches. Clumps of cordgrass or seeds can break off and wash across bays and root in new areas. Cordgrass reduces open mud feeding habitats of shorebirds, competes with indigenous salt marsh vegetation, and alters the hydrology, structure, and function of wetlands. Once established, controlling and managing cordgrass is extremely difficult and expensive.

How Can We Stop It?

Do not purchase, plant, or trade this species. The Washington State Noxious Weed Control Board has listed spartina as a Class A noxious weed. Diking may be used as a way to confine the lateral spread of rhizomes. Seedlings can be hand pulled or covered with a geotextile fabric. Mowing spartina repeatedly also has reduced larger infestations. A planthopper (prokelisia marginata), was released in Washington in 2000 as a biological control agent for smooth cordgrass and it has significantly reduced seed survival at some sites.

What Are Its Characteristics?

  • Spartina alterniflora is a tall, clumping, perennial grass, growing 2 to 7 feet in height with creeping rhizomes
  • Leaves have flat blades and can be 1/4 to 3/5 inch wide and 12 to 20 inches long
  • Ligules, the outgrowth from the sheath of the leaf blade, consist of a fringe of hairs
  • Stems are hairless and hollow
  • Flowering occurs from June to November
  • Flowers grow from 4 to 16 inches tall and about 1/3 to 1 inch wide, each made up of 5 to 30 flowering spikes

How Do I Distinguish It From Native Species?

Spartina may resemble native sedges (carex spp.), or other grasses like saltgrass (distichlis spicata), tufted hairgrass (deschampsia caespitosa), or American dunegrass (leymus mollis). Grasses like spartina have hollow stems that distinguish them from sedges. Seed and flower heads are the most reliable way to distinguish between different species of grasses.

Additional Photographs