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Prairie Creek knotweed and reed canary grass control

Prairie Creek Before 1
Prairie Creek Before 3
Prairie Creek After


Grays Harbor County, city of Taholah

Project Summary

In 2007 NRCS and the Quinault Indian Nation (QIN) develop Integrated Pest Management (IPM) plan. The IPM provided strategies for prevention, avoidance, monitoring, and suppression of invasive plant species and other pests.

Currently, QIN is using IPM strategies to control knotweed, an invasive species, in 135 acres of riparian forest along an 8 mile stretch of Prairie Creek, a tributary to the Quinault River noted for one of the most productive steelhead and salmon spawning areas. Control of Giant, Japanese, and Himalayan knotweeds was identified as a treatment priority in the IPM plan. Knotweed is a strongly rhizomatous perennial species with lateral rooting up to 30ft, growing up to 12 feet in height and in very large patches, dominating the native plant community. The knotweed forms a closed canopy and shades out the existing plant communities, forming a monoculture. This species is not used by wildlife for forage or habitat. Control of invasive weed species in riparian forests contributes to restoration of habitat critical to fish and wildlife by allowing desirable plant communities to respond, expand, and reoccupy habitat following weed control activities. WA State Salmon Recovery Funding Board funded the first 5 years of knotweed suppression in Prairie Creek. The area of knotweed infestation was reduced by 95%. NRCS provided financial assistance to implement the prevention, avoidance, and monitoring strategies of the IPM plan and to document the results of the suppression activities. NRCS also contributed funding to plant Sitka Spruce in small portions of the treatment area. Accepted, long-term, control strategies developed by Extension and state Weed Control agencies include several years of follow-up spraying of re-sprouts which are activated from either dormant rhizome nodes or the end of the rooting structure that may not have been affected by the treatment. Without this follow-up control work, the knotweed once again will quickly dominate the site. Therefore, NRCS is now providing financial assistance to implement weed control and habitat management practices and fully restore riparian forest habitat in Prairie Creek watershed through 2016. NRCS is also helping QIN to control reed canary grass, another invasive species, which has become established in some of the knotweed treatment areas with the capacity to dominate small waterways making them unusable for spawning habitat by salmonids. Integral to a successful suppression strategy is continual monitoring of the response by native species to the removal of the weed species and that is an important component in the current conservation plan developed by NRCS and QIN. Implementation of the monitoring strategy will help guide QIN’s continuing effort to restore and maintain the native riparian forest in Prairie Creek and throughout the Quinault Indian Reservation. Other QIN knotweed treatment projects 4 acres of suppression along Lunch Creek (funded by NRCS 2010-2012) Lower Quinault River tributaries (2010-Ongoing) Quinault River, Lake Quinault shoreline and the town of Neilton (off reservation).  

Conservation Partners

Quinault Indian Nation, NRCS, USFS, EPA, WA State SRFB, Grays Harbor Weed Board.

Resource Challenges

Habitat Degradation; Degraded Plant Condition-Excessive Plant Pest Pressure; Excessive Bank Erosion from streams, shoreline and water conveyance channels; Water Quality Degradation–Excessive Sediment in surface waters. Riparian forest is important habitat for elk and other terrestrial wildlife species and provides many benefits to the aquatic organisms’ habitat, including pacific salmon populations. Invasive plant species degrade forest health and disrupt the natural succession of the native plant community. Native vegetation helps limit stream bank erosion and sediment delivery to surface water bodies, shades the streams and helps maintain water temperatures beneficial to aquatic organisms, and provides nutrients to the aquatic ecosystem.

Conservation Programs Used

Environmental Quality Incentives Program (EQIP).


Quinault Indian Nation, a founding member of the Quinault/Queets Cooperative Weed Management Area group, worked with NRCS, USFS, EPA, NPS, WA DNR, WA State SRFB, Grays Harbor Weed Board to address shared resource concerns on and off the reservation and across different land ownerships, private, public, and tribal. The comprehensive approach to invasive species control and habitat restoration provides a model for others to use.


Invasive species control is an ongoing project for QIN and its partners. In Prairie Creek, knotweed has been significantly reduced and continual monitoring with light spot treatments will be needed until several years of no evidence of the plant remains, this could be possibly be 10 years from now due to the extreme amount of knotweed that inhabited the 8 miles of river over a very long time before treatment started. The best plan for control and eradication of invasive plants, such as knotweed, is the implementation strategy of early detection and rapid response. Plant community enhancement may be a future opportunity to further restore the riparian forest habitat. WA State SRFB and NRCS, at least, should have abundant opportunities to work with QIN to meet that common goal.


Scott S. Cook, Resource Conservationist
Montesano, WA
(360) 249-5900 ext. 101

NRCS, Winter 2013

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