The purpose of the Columbia Basin Cooperative Weed Management Area is to work cooperatively and collaboratively to address cross-boundary invasive species issues, focusing on flowering rush (Butomus umbellatus), in the Columbia Basin.

What Is The CWMA?

The Columbia Basin Cooperative Weed Management Area was created in 2017 to work collaboratively on invasive species issues within the basin.  A Columbia River Basin CWMA brings together agencies, work groups, and smaller-scale groups to provide a coordinating body to address basin-wide issues.

About Us

The Steering Committee of the Columbia Basin CWMA consists of the following partners; Alberta Environment and Sustainable Resource Development, Columbia River Inter-Tribal Fish Commission, Kalispel Tribe, Montana Fish Wildlife & Parks, Montana Invasive Species Council, Oregon Department of Agriculture, Portland State University, US Army Corps of Engineers, Washington Department of Agriculture, Washington Invasive Species Council, Washington State University, Washington Department of Ecology and Western Invasives Network.

CWMA Scope

About The Issue

The primary focus for the Columbia Basin CWMA is flowering rush. Flowering rush (Butomus umbellatus L.) is an herbaceous aquatic perennial in the family Butomaceae. Native to Europe and Asia, B. umbellatus was introduced into North America by 1900, possibly both accidentally in ballast and packing material and intentionally via the horticulture trade. It is now widely naturalized in wetlands, lakes, ditches, and slow-moving rivers in 21 states and 8 provinces surrounding the USA/Canada border, and is continuing to expand outward. Butomus umbellatus displaces native plant species, impedes water flow, alters habitat structure and nutrient cycling, damages fishing, hunting, boating, and other recreational sectors, and is difficult to control. By working collaboratively across the Columbia Basin, the Columbia Basin CWMA hopes to find ways to minimize the impacts and limit the spread of this invasive aquatic plant.

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 Completed Projects and Focus

The Columbia Basin CWMA is a coordinating body that seeks to boost basin-wide work on the important issue of invasive plants, focusing initially on flowering rush. It is the CWMA’s intention to bring together leaders from across the Columbia River Basin that will provide long-term leadership for the CWMA. Fostering information sharing on management and best practices for control and monitoring focus our work.

Flowering Rush


On February 27 and 28, 2018 the Cooperative Weed Management Area held a regional summit focusing on flowering rush within the Columbia River Basin. The summit provided a forum to share information about current efforts and needs, and the best available science. The summit dialog helped inform a framework for a regional management plan to address the challenges in managing flowering rush. Learn more about the Flowering Rush Summit:

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Flowering Rush

Management Plan

A regional management plan was completed in 2019 to help drive research, management, restoration and other activities for the future. This plan is a tool to engage policy and decision makers to build support for flowering rush issues.  Discussions at the Flowering Rush Summit facilitated helped to inform key content areas of the management plan.

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Get Involved

Keep up to date on CWMA activities – sign up for our list serv. Contact the coordinator to learn more.

 CWMA Partners