SEQUIM (Sept. 19, 2005) – Jamestown S’Klallam Tribal crews this summer are combing the Dungeness River for two invasive weeds – knotweed and buddleia. Both are aggressive, non-native plants and both are a serious threat to salmon habitat along the river in Sequim.
“These weeds establish themselves quickly and out-compete native plants that are important for creating and maintaining fish habitat along the Dungeness River,” said Hilton Turnbull, Forest and Fish biologist for the Jamestown S’Klallam Tribe, while injecting a knotweed cane with an herbicide-filled, needle-tipped gun. “What we are doing is mapping the weed occurrences and monitoring how effective our treatment methods are for control from one year to the next.”
Knotweed and buddleia are often used as ornamental plants for gardens. Knotweed, which can grow as large as 20-feet tall, comes from Asia and is commonly known as “false bamboo.” The plant has large oval shaped leaves with pointed tips and produces clusters of tiny white flowers. Buddleia also comes from Asia, as well as Africa, and is commonly referred to as “butterfly bush.” Buddleia, which resembles a green shrub, grows as large as knotweed and produces a cone-shaped cluster of purple flowers.
While the plants might be popular with gardeners, they are a bane to habitat biologists. Both weeds degrade fish habitat by spreading rapidly and taking over large stretches of the riverbank, impeding the growth of important native plants, such as cottonwood and cedar. Cottonwood and cedar trees are essential for healthy salmon spawning and rearing habitat. Trees provide shade that cools the water, keeping it at an ideal temperature for fish, and, overtime, those trees will fall into the stream helping create pools and rifles for spawning salmon.
To retain the benefits of a healthy riparian – streamside – ecosystem and ensure invasive species do not take over the river, Turnbull and his crew are surveying the river and floodplain by mapping the weeds with a Global Positioning System. So far, they have mostly concentrated on knotweed, but plan on battling buddleia in the next year. After documenting the knotweed, larger canes are injected with herbicide and smaller stalks are sprayed.
The Jamestown S’Klallam Tribe’s project, which includes public outreach to landowners who might be unknowingly contributing to the problem, is funded by a U.S. Environmental Protection Agency grant. Clallam County is supplying herbicide and technical assistance through a cooperative agreement with the tribe. The county also is helping with other tribal invasive species control projects on the North Olympic Peninsula. That has allowed tribes to allocate more grant funding for control and monitoring efforts.
Mechanical methods of removal don’t really work for these plants. In fact, mowing or chopping the invasive weeds only helps them spread. And that’s partly how they became a problem on the Dungeness River. All it takes is a small stem or root to escape from a knotweed bush to create a colony. Stems float down the river, anchor themselves to the riverbank and begin growing. Buddleia spreads itself by seed after it flowers.
“Knotweed canes and buddleia seeds move around the river pretty readily,” Turnbull said. “Flooding scours plant material and deposits it among logjams, on gravel bars and throughout the maze of side channels in the floodplain.”
Almost 9 miles of the Dungeness River needs to be mapped and treated for the weeds. That’s a considerable distance, but compared to the Dickey and Hoh rivers on the Washington coast, it’s rather small. Coastal tribes are trying to tackle the knotweed problem on those rivers, where the weeds have exploded along the riverbanks covering nearly 30 miles in one case.
“Based on this year’s survey results, we are seeing a reduction in area and distribution of the knotweed infestation, but we’ve really got our hands full with buddleia; in some cases it is the dominant woody vegetation on gravel bars and along the forest,” Turnbull said. “All the tribes and local governments on the west side of the Olympic Peninsula are doing their best to address the invasive plant species and prevent their reintroduction into our river systems.”
For more information, contact: Hilton Turnbull, Forest and Fish biologist for the Jamestown S’Klallam Tribe, 360-681-4603, [email protected]. Darren Friedel, information officer for the Northwest Indian Fisheries Commission, (360) 297-6546, [email protected].