Hoh Tribe Slated To Begin Knotweed Eradication Program

HOH RESERVATION (Oct 14, 2002) — The Hoh Tribe will soon begin an aggressive multi-year campaign to eliminate the invasive plant knotweed from the banks of the Hoh River. The weed threatens streamside forests and natural river function.

Japanese knotweed, imported as an ornamental from Asia in the late 1800’s and often found as an ornamental bush in gardens, spreads quickly, and can overrun all plants around it. It is even able to out-compete other notorious invasive plants such as Scot’s broom. It is commonly known as false bamboo. It threatens fish habitat throughout the State of Washington.

Because it can grow as much as 16-feet in one season, the plant can alter many of the salmon habitat-forming and food production characteristics of streamside forests. In other areas of the Olympic Peninsula, the plant is known to reduce the amount of gravel available for salmon spawning beds. Japanese knotweed also requires a great deal of water, stealing it from adjacent native plants. The plant has no natural predators or diseases. Like most imported plants, it isn’t eaten by native insects or animals. Knotweed is classified as a Class B noxious weed in Washington meaning that it’s already spread too far to require control by landowners.

An inter-agency group was assembled by the Hoh Tribe and trained in knotweed control methods. Phil Burgess of the Clark County Weed Control Board led the training. Burgess has studied knotweed and environmentally-friendly control methods for more than five years. He taught the group how to inject each stem of the plant with a weed killer. Participants included representatives from Olympic National Park, U.S. Forest Service, Quileute Tribe, and Clallam and Jefferson County Weed Control boards.

The individual injections are necessary to be effective without spreading large amounts of chemical spray into the watershed. “Spray and mowing are neither effective nor safe,” said Silver. “You have to spray year after year, which spreads herbicides into the air and water, and mowing means you have to dispose of the plant material in such as way that it won’t have the potential to spread elsewhere.

Using Pacific Coastal Salmon Recovery funding, the Hoh Tribe is working quickly to eradicate the newly established plant from the river corridor. “Knotweed can spread by very small root and stem fragments, and it especially likes new gravel bars created every winter when the river floods and changes course into new channels,” said Jill. “It has the capacity to completely take over a river or creek’s floodplain in a very short time, and once it’s established, it’s believed to be impossible to get rid of,” said Jill Silver, habitat biologist for the Hoh Tribe.

The tribe’s habitat program initiated a survey in 2002 to map the extent of the spread by recording the location, size, and ranking of the plants most likely to be moved by erosion or river action. Eradication plans had to be revamped when tribal natural resources staff discovered that instead of a few plants, there were hundreds over miles of river corridor, requiring a different elimination strategy.

The eradication project is expanding within the region. The Quileute Tribe is working with Clallam County to write a proposal to the Salmon Recovery Funding Board for rivers north of the Hoh where the problem is more widespread.

The tribe wants to inform the public about the weed by posting information at boat ramps and parks. “People need to understand how much of a problem this plant is becoming to river restoration. They can help by reporting plant locations and by not moving it around by picking it,” said Silver. “Both Clallam and Jefferson Counties have weed control boards that provide information about noxious weeds and can assist in their control,” said Silver.


For More Information, contact: Jill Silver, Habitat Biologist, Hoh Tribe, (360) 374-6735; Steve McGonigal, State Weed Control Board, (360) 902-2053, www.wa.gov/agr/weedboard/; Cathy Lucero, Control Coordinator, Clallam County Noxious Weed Board, (360) 417-2442; Carol Dargatz, Control Coordinator, Jefferson County noxious Weed Board, (360) 379-5610 ext. 303; Debbie Preston, Coastal Information Officer, Northwest Indian Fisheries Commission, (360) 374-5501