Roesiger Invasive Plant Control Project

Review the Roesiger Integrated Aquatic Vegetation Control Plan and recorded presentation by clicking on the links below.


Provide Your Feedback by Taking the Survey (one per household) by OCTOBER 24: 


In 2021, Snohomish County Surface Water Management and the Lake Roesiger Community and Boat Club are partnering together to develop an Integrated Aquatic Vegetation Management Plan (IAVMP) for Lake Roesiger. The plan will focus on long-term control of key invasive plants, and will be developed with in-depth community engagement. 

The Issue
Lake Roesiger is home to an abundance of native plants. These beneficial plants are vital to keeping lakes healthy. They provide important food and habitat for aquatic life including fish, turtles, frogs waterfowl and other aquatic life. They also are important for us as they help to clean the lake by filtering pollution and prevent shoreline erosion. 

Unfortunately, Lake Roesiger is also home to a few non-native, invasive plants. These plants can crowd out the beneficial native plants, harm lake ecology, and interfere with swimming, fishing and boating. So while it is important to keep native plants in the lake, it can be desirable to manage invasive plants to reduce their impacts. 

The lake has three invasive species of concern in the lake basin - Eurasian watermilfoil, fragrant waterlily and narrow-leaved arrowhead. There are also three invasive species found on the lake shoreline - yellow flag iris, purple loosestrife and Japanese knotweed. See our aquatic plants page to learn more about the different types of plants and how to identify them. 

Fragrant waterlily

Introduced as an ornamental plant, it takes over shallow areas, limiting habitat and boating. It also causes the lake to fill in faster. 

Fragrant Waterlily Patch and Flower
Fragrant Waterlily Patch and Flower

Fragrant waterlily

Introduced as an ornamental plant, it takes over shallow areas, limiting habitat and boating and speeds causes the lake to fill in faster.

Eurasian watermilfoil

Noxious weed, grows in hard to swim through mats and crowds out native plants. Can reduce oxygen in the water. Easily regrows from broken fragments.

Eurasian Watermilfoil Patch and Flower

Grass-Leaved Arrowhead

 Less researched, may displace natives plants and wildlife, can be a nuisance to swimmers. Found only in 5 lakes in the state, including Lake Roesiger.

Grass-leaved Arrowhead Patch and Flower

Yellow Flag Iris

Grows in dense clumps in shallow waters of lakes and streams. A piece of root can break off and grow a new plant. Resin from it can irritate the skin.  

Yellow Flag Iris Patch and Flower

Purple Loosestrife

Emerges from the water in dense stands, spreads rapidly. Crowds out plants that make for good nesting habitat. Could be mistaken for spiraea or fireweed 

Purple Loosestrife Patch and Flower

Past Efforts

Since 1998 Snohomish County controlled Eurasian watermilfoil in the lake through diver surveying and hand-pulling. These efforts were effective in keeping milfoil levels low with only small patches growing each year. Unfortunately, funding for this program was lost in 2017. The Community Club has raised funds to hire divers for some hand-pulling work in 2019 and 2021.

Over the years, some individuals have worked to control fragrant waterlilies in from of their properties. However, the problem has persisted and there was a growing desire to have a larger solution. In recent years, the Community Club has purchased tools for homeowners to do lily control on their property and obtained a larger permit for participating landowners to lay bottom barriers. While these efforts may provide relief in small areas, they are not addressing the large scale infestation.

The Integrated Aquatic Vegetation Management Plan

In 2020, the community approached the County for assistance in applying for a  Washington State Department of Ecology grant program to help fund invasive plant control. The program requires that an Integrated Aquatic Vegetation Management Plan first be developed before communities can obtain funds for control work. The County applied for and was awarded a grant beginning in July 2021. 

Plan Goal & Steps 

Roesiger Plan Timeline Of Actions

The grant's goal is to provide the community with a road map which will help native plants, ecosystem health, and lake recreation. The plan will lay out all options with associated costs and benefits so the community can decide on the best path forward. 

Step 1

Map Invasive Species

In July 2021, County staff will conduct a survey of the lake mapping all locations of identified invasive species as well as inventorying the native plant species. These maps will be used to assist in the plan development.

Step 2

Develop Draft Management Plan

Snohomish County has contracted with Tetra Tech Inc. and ESA to develop the draft plan. TetraTech and ESA have extensive experience managing invasive aquatic plants including knowledge of the latest research in control technology. They also have experience working with local communities to facilitate development of  IAVMPs. Members of the Lake Roesiger Community and Boat Club will be instrumental in developing the draft plan. The Club has appointed a steering committee of 11 members with representation from each lake basin. The committee will first meet to provide input to Tetra Tech and ESA regarding the plan goals and control options of interest. The committee will again meet to review the draft plan and develop potential recommendations that the the larger lake community can then choose and vote on.

  • Steering Committee Meeting 1: August 9, 2021 - development of plan goals and control options. Watch the recorded meeting HERE and view presentation HERE.
  • Steering Committee Meeting 2: Scheduled September 9, 2021 -  review draft management plan and develop recommendations. Watch the recorded meeting Watch the recorded meeting HERE and view presentation HERE.
Step 3

Present Draft Plan to Community for Input

Once the draft plan has been developed, Tetra Tech  and ESA will provide an online presentation to explain the plan and the potential management options. The entire lake community will be able to view the presentation and the draft plan. The community will also receive an online survey to provide feedback on the plan and the potential control options.

Step 4

Community Meeting and Online Vote to  Finalize Plan

Finally, there will be a lake-wide community meeting to review the plan feedback. The community can then discuss and vote on the desired options and decide on next steps. It is anticipated that if the community agrees upon a future option, the County would then work with the community to apply for a grant to implement the plan starting in 2022.

Community Meeting is scheduled for October 26, 2021 6:30 - 8:30 PM via Zoom.

Join Zoom Meeting:
Meeting ID: 937 5865 2322
Join by phone - Dial by your location (253) 215-8782

Cast your vote Oct 28 - Nov 10: Following the meeting there will be an online community survey where everyone can vote on the final options. The survey link will be added on this website following the community meeting.