The Edmonds Marsh is one of the few urban, tidally influenced saltwater estuaries remaining in the Puget Sound area. The marsh once occupied nearly 40 acres, which has been reduced to 22 acres in the present day due to urban development. As part of an ongoing effort to restore native plant communities in the Edmonds Marsh, specialists from the Snohomish County Noxious Weed (SCNW) program will visit the Marsh on Monday, October 2nd to continue the process of eradicating an infestation of common reed (Phragmites australis).
Phragmites is a noxious weed requiring control in Snohomish County. This effort will ensure that the City of Edmonds continues to remain in full compliance with the law. Phragmites is a highly invasive grass that forms dense monocultures in wetlands, altering the structure of local ecosystems, reducing biodiversity, and degrading habitat quality. Two Phragmites patches have become established in the northern part of the Marsh and will continue to spread through a dense underground network of rhizomes if left untreated.
The ecological characteristics of Phragmites make it nearly impossible to control by non-chemical means. The County team will treat affected areas using ‘spot’ applications of Imazapyr, an herbicide categorized by the EPA as practically non-toxic to fish, invertebrates, birds and mammals. Herbicide is applied only to the target plants while avoiding the surrounding plants and soil; if strong wind occurs, application will stop to prevent the herbicide from drifting to unintended locations. Phragmites were initially treated by the County in 2021, and the team has continued to monitor the area and conduct follow-up treatments each fall as necessary. As Phragmites are reduced, native plants including Baltic rush (Juncus arcticus), Lyngbye’s sedge (Carex lyngbyei) and seashore saltgrass (Distichlis spicata) are expected to naturally re-colonize the treated areas. While they are on site, the County team may also treat Japanese knotweed (Fallopia japonica).
The eradication effort is consistent with the City of Edmonds Integrated Pest Management (IPM) approach to parks maintenance, which prioritizes the use of physical, mechanical, and biological control methods. Chemical treatments are used only when other control efforts would not be effective, as is the case with the current infestations of Phragmites and knotweed.
Historically, the Edmonds area including the Marsh was used by a fishing village by the Coast Salish Native Peoples to sustain their livelihoods including fishing, shellfish gathering, and harvesting of plants to make clothing, mats, and baskets. This tradition continues today under tribal fishing rights along the Edmonds waterfront. After urbanization, the railroad and man-made barriers blocked the tidewater flow, creating a freshwater-dominated wetland fed by Willow Creek and Shellabarger Creek. In 1988 the saltwater flow was reestablished by opening the tide gate most of the year. The site now contains diverse wildlife habitat supported by both fresh and saltwater vegetation.
You can learn more about how the City manages plant and animal pests in parks by visiting Edmonds Plant and Pest Control Efforts.