It’s not every day you find a new noxious weed in your county, but this August King County had one of those days. On August 15th, our program was alerted to an infestation of the Class A noxious weed ricefield bulrush (Schoenoplectus mucronatus) growing in a wetland just east of Redmond. Sean Davis with Ridgefield National Wildlife Refuge in Clark County helped confirm the ID of the species. Prior to this discovery, the main known location of this plant in Washington state had been in the Ridgefield refuge, along with a few other populations in southwest Washington, such as Beacon Rock in Skamania County and Whipple Creek (part of Salmon Creek) in Clark County.
On August 16th, Aquatic Lands Specialist Ben Peterson, County Lands Specialist Roy Brunskill, Regional Weed Specialist Patrick Sowers, and Riparian Projects Team Member Kirk Massee visited the site to control the infestation.
Ricefield bulrush is an introduced species of perennial bulrush with triangular stems that grow 2-3 feet tall. It reproduces by seed as well as via rhizomes and stolons, making it especially difficult to control. Each culm (stem) produces 4-20 rust-colored flower clusters with greenish centers. The uppermost bract beneath a flower cluster is spreading to reflexed and 0.4-3.9 inches long. Blackish-brown seeds develop summer-fall. Each stem has 1-2 reduced, bladeless leaves.
Ricefield bulrush, native to parts of Europe, Africa and Asia, is a weed in at least 43 countries, often growing—as the name implies—in rice fields. It can also be found in wetlands and other areas with moist soils, such as ditches. This plant is known to be resistant to herbicides, making it especially tough to get rid of. In Clark County, they’ve resorted to painstakingly pulling up all of the plants.*
If you think you’ve found ricefield bulrush growing elsewhere in King County, please let us know! You can call us at 206-477-WEED (206-477-9333) or email noxious.weeds@kingcounty.gov. Please include a photo or specific location so we can confirm the ID. There are look-alike native species so make sure to get a positive ID before controlling. See these pages for photos of ricefield bulrush and a native look-alike:
- Noxious weed: ricefield bulrush (Schoenoplectus mucronatus)
- Native look-alike: slender flatsedge (Cyperus bipartitus)
*For more information on ricefield bulrush, visit the following pages (sources of the above information):
Washington State Noxious Weed Control Board: Ricefield Bulrush
Clark County Vegetation Management Program: Ricefield Bulrush