What is it?
Spartina species are aquatic grasses that grow on the mud flats and marshes of Puget Sound and our coastal estuaries. The plants tend to grow in circular clumps called ‘clones’ and are bright green in color. Smooth cordgrass came to Washington State 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 outcompetes native plant species, including rare and endangered plant species, reducing marsh biodiversity and ecological functions.
Is it here yet?
Yes. Spartina can be found in parts of Puget Sound, Grays Harbor, and Willapa Bay. It has also been reported in Kitsap, Mason, and Jefferson counties, and small populations were recently located near the mouth of the Columbia River.
Why should I care?
Rhizomes from a single plant spread outward in all directions, eventually forming large extensive patches or meadows that are difficult to eliminate. Clumps of cordgrass can break off and wash across bays and root in new areas. Seeds can spread long distances by floating on racks of dead stems in the fall. Cordgrass reduces open mud feeding habitats of shorebirds, competes with indigenous salt marsh vegetation, and alters the hydrology, structure, and function of wetlands.
What should I do if I find one?
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 can 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 State in 2000 as a biocontrol 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). Other noxious weeds such as the common reed (Phragmites australis) also look similar.
Where can I get more information?
- Washington State Noxious Weed Control Board
- Plant Conservation Alliance
- University of Florida's Center for Aquatic and Invasive Plants
- Invasive Species Specialist Group's Global Invasive Species Database
- Willapa National Wildlfe Refuge's Report "Introduced cordgrass, Spartina alterniflora Loisel., in salt marshes and tidelands of Willapa Bay, Washington," by Kathleen Sayce