Sustainable landscape management is an important value in our community. We were recently recognized as the first residential development to be Salmon-Safe certified, and as part of our commitment to protecting biological diversity we choose to eliminate and control invasive species using manual methods instead of herbicides.

Last weekend a group of Willamette University students participated in a creek restoration work party to tackle the Japanese knotweed growing along our stretch of Pringle Creek. Japanese knotweed is a highly invasive species that devastates natural riparian areas because it spreads rapidly and prevents the propagation of native species. Here’s what the site looked like before our work party:

Our strategy for knotweed removal without chemical agents follows the guidelines devised by the King County Noxious Weed Control Program. The students carefully cut the stems close to the ground and dug up as much of the root system as possible.

The plant matter must be quarantined until it completely dies, and then we can compost it. After the students dug up the roots, we covered the site with overlapping thick canvas fabric and several yards of mulch to suppress any new growth. Here’s what the site looks like after all their hard work:

We hope that our efforts will demonstrate the feasibility of herbicide-free eradication of invasive species. Japanese knotweed is a particularly resilient weed, and total eradication will likely take years of manual control. However, the hard labor is worth it because it means we will not cause further harm to the creek and surrounding riparian area. It’s really easy to use an herbicide and consider the weeds “taken care of”, but to consider the long term environmental impacts of weed control is a much more rewarding task.

Thanks to the Willamette University student volunteers! Also thanks to the City of Salem for their generous Watershed Protect and Preservation grant!