A classic case of good intention gone bad, English cordgrass (Spartina anglica) was introduced to Washington around 1962 to stabilize dikes and provide forage for cattle. The U.S. Department of Agriculture imported seeds from England, and a WSU extension agent planted the seeds near Stanwood in the Stillaguamish Estuary.
English cordgrass has since infested large areas around Stanwood, particularly Port Susan Bay, Skagit Bay, Admiralty Inlet, and Saratoga Passage. It has also spread, with disastrous environmental effect, to other parts of Puget Sound, including Camano Island, Whidbey Island, and the San Juan Islands.
Due to its tenacity, its rapid growth rate, and its ability to spread via seeds and fragments, cordgrass has been very difficult to control. Despite nearly a million dollars and four years of effort, English cordgrass in Puget Sound has been reduced by only about 13 percent. WSU biologist Sally Hacker and graduate students Eric Hellquist and Tabitha Reeder are working with state personnel and county weed control crews to refine the focus of control efforts and gather data on cordgrass invasions. Funding for their research comes from the National Sea Grant Program with help from Washington Sea Grant Program. In addition, Hellquist’s work has been supported by the National Estuarine Research Reserve System, Betty W. Higinbotham Trust, and WSU College of Sciences.
Because the extent of English cordgrass invasion in Washington was not known, Hacker, Hellquist, and University of Washington scientist Megan Dethier conducted surveys and analyzed data from the Washington State Department of Fish and Wildlife and Washington State Department of Agriculture. They found that English cordgrass has invaded 73 sites covering some 3,300 hectares, occurring primarily in mudflats and low-salinity marshes.
As cordgrass spreads, it converts salt marshes and open mudflats into dense cordgrass monocultures that do not offer the types of food and living conditions needed by oysters, clams, worms, and micro-crustaceans. The loss of these species affects others in the food chain such as birds and fish. Additionally, floating mats of dead cordgrass can smother some plants and animals.
“This species is amazing,” says Hacker, “because it can invade four very different habitats.”
Because of environmental and commercial effects of English cordgrass invasion, state and county agencies began removing some of the thick mats and widely dispersed propagules in 1997. Removal is a labor-intensive process of digging small clumps or mowing and applying herbicide to large clumps. The large clumps are very tenacious, and in order to kill them, workers must mow and spray repeatedly for about five years.
Each WSU researcher is tackling specific questions about the invasion. Hacker’s research targets factors that influence invasive success and effectiveness of control efforts.
Reeder maintains framed plots to learn how much the cordgrass has grown in the past year. Some of her plots have been previously treated to remove cordgrass. Her data so far show that one or two years of treatment only slightly reduces regrowth. However, if the dead thatch, called wrack, is anchored in place, it reduces canopy regrowth by 50 percent and eliminates new flowers and seeds.
At the Padilla Bay National Estuarine Research Reserve, where the reserve staff has to control Spartina each year, Hellquist is assessing soil and habitat characteristics. At other sites around the sound, he is investigating how English cordgrass interacts with native vegetation and how native vegetation returns to areas where cordgrass has been removed.
Hellquist also works with Biological Sciences faculty member Ray Lee and graduate student Brian Maricle to quantify levels of sulfide, a naturally occurring soil toxin. Spartina can grow in physical conditions that are considered harsh even for intertidal plants, and they would like to understand the range of conditions it inhabits.
Lee and Maricle are also studying a relative of English cordgrass that has invaded in Puget Sound and in Willapa Bay and Gray’s Harbor on the coast. Smooth cordgrass (S. alterniflora) was introduced accidentally by the oyster industry in Willapa Bay and is a serious threat.
Smooth cordgrass has an interesting connection to English cordgrass. From its native habitat in eastern North America, it was introduced to England where it hybridized with a native species, small cordgrass (S. maritima). About 1892, this infertile hybrid underwent a natural process in which its chromosome number doubled and became a fertile species, English cordgrass (S. anglica). This new species quickly spread across nearby marshes and currently covers about 10,000 hectares in England.
Upcoming studies will focus on seed production hotspots and effects of timing of herbicide application on seed production. “The resource managers and field crews are working very hard,” says Hacker, “but this will require a long, concerted effort—we’re battling a difficult invader.”