2019 Invasive Plant Project: North Santiam River Invasive Water Primrose Treatment and Survey

By: Jenny Meisel Native and Invasive Plant Specialist

Marion SWCD will be partnering with the North Santiam Watershed Council this summer and fall to tackle invasive water primrose (Ludwigia hexapetala or peploides) in the North Santiam River.  Two large and 2 small infestations were found last fall between Lyons and Stayton.  The goals for the project in the North Santiam watershed are to:

  • initiate treatment of approximately 38 acres (in 4 sites) of recently discovered water primrose infestations;
  • conduct surveys on 13 river miles on the mainstem North Santiam River in Marion and Linn Counties from Lyons to Stayton;
  • launch an awareness campaign to inform local residents of the devastating impacts this invasive species can have on the aquatic ecosystem.

Treatments and surveys will be conducted by professional contractors.  Funding for this project comes from an Oregon State Weed Board Grant.

If you live along the North Santiam River or a tributary to the North Santiam River and are willing to allow access for surveys, please contact Jenny Meisel or Sarah Hamilton at 503.391.9927 or [email protected] or [email protected].

  Water primrose is an aquatic perennial herb that forms large dense mats.  It grows up to 3 feet tall and is found in sloughs, ponds and other waterways with slow or still water.  The flowers bloom from mid-summer through fall and are showy and yellow with 5 petals.  This plant has significant impacts on wildlife: Turtles, fish, ducks, and other wildlife cannot swim through infested areas, limiting available habitat.  Dense mats block sunlight, killing off native aquatic plant species.  The plant is originally from South America and has expanded significantly in Western Oregon in the past 10 years.  Large infestations in Marion County occur in sloughs in Minto Brown Island Park and at Willamette Mission State Park.  Other agencies and organizations are currently working to control these large infestations.

If you think you have found water primrose anywhere in the North Santiam Watershed or in other parts of Marion County, please report infestations to the Oregon Invasive Hotline: www.oregoninvasiveshotline.org

Information on water primrose compiled from: City of Eugene, Washington Department of Ecology and Oregon Department of Agriculture