Roesiger Invasive Plant Control Project

Overview

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 by providing habitat, limiting erosion, and filtering pollution. However, the lake suffers from the the introduction of non-native, invasive plants. These plants crowd out native plants hurting both the lake ecology and recreation.

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. 

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. 

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, individuals have worked to control fragrant waterlilies on their landowners. 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 appyling 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

Snohohmish County has contracted with TetraTech Inc. to develop the draft plan. Their staff has extensive experience managing invasive aquatic plants including the latest research in control technology. They also have experience working with local communities to facilitate development of  IAVMPs. Both the County and Tetratech will work closely with the Lake Roesiger Community and Boat Club to develop the draft plan. The Club has appointed a steering committee with representation from each lake basin. The committee will provide input to TetraTech regarding the plan goals and management options to explore as well as review the draft plan to develop management options from which the larger lake community can then choose and vote on.


Step 3

Present Draft Plan to Community for Input

Once the draft plan has been developed, TetraTech 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 a survey to complete to provide feedback on the plan and the potential control option.


Step 4

Community Meeting to Finalize Plans

Finally, their will be a lake-wide community meeting to review the plan feedback. The community can then 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.