Johnson Creek – Willamette Confluence Salmon Habitat Enhancement
Streamside Reforestation Projects
CreekCare in Rural Clackamas County
Mill Park Riparian Plantings
Johnson Creek-Tacoma MAX Salmon Habitat & Interpretive Boardwalk
JCWC Office Restoration
Invasive Knotweed Removal
The primary goal of the Johnson Creek Watershed Council (JCWC) is to protect, restore, and enhance the Johnson Creek Watershed. One of the many projects undertaken to achieve that main objective has been the removal of Japanese Knotweed, an invasive plant species that crowds out native plants and contributes to erosion and key streamside habitat loss. Since funding was received in 2006, JCWC and other organizations have monitored and treated Knotweed along the length of Johnson Creek with much success.
Who funded this project and who works with JCWC on it?
The project began in 2006 when the JCWC received funding, mainly from the Oregon Watershed Enhancement Board, to start an ambitious program to remove Knotweed along the length of Johnson Creek. Noah Jenkins, the Education and Research Associate here at JCWC, has been involved in this program from the start. Alongside him, the East Multnomah Soil and Water Conservation District has played a large role in removing the Knotweed as well as the cities of Portland, Gresham, and Milwaukie. Hundreds of private property owners were involved and in total, treatment crews performed remedial work on over 160 private properties.
What is the treatment process like and how effective is it?
During the first two years of this project, the process of removing Knotweed involved injecting each individual stem with glyphosate herbicide. This was hugely successful, with a 90% rate of eradication. After two years, the method of herbicide application switched from stem injection to foliar treatment. This was due in part to the intensive nature of injection as well as the issue of Knotweed regrowth being too small at the stem for an injection of herbicide.
What does the future hold for this project?
The push to remove Knotweed from Johnson Creek has been particularly effective. The original grants supporting the initial work expired in 2008, but due to the success of the first two years, monitoring and treatment costs are now low. Many patches along the creek have shown no regrowth since the first treatment. However, Knotweed is a resurgent plant, evidenced by the data collected by the Nature Conservancy. Their work on the Sandy River has shown that areas can experience one to two years of no regrowth, only to have Knotweed come back the following season. In regard to Johnson Creek, JCWC believes that despite eradication rates of over 95% since 2006, monitoring and treatment will be required every two to three years and that this program should continue as long as it is necessary to ensure that Knotweed does not get out of hand.