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If you have taken a walk through Yesler Swamp this past spring or winter you may have noticed a couple restoration projects taking place. Near the viewing platform, along both sides of the boardwalk, is the location of one of these projects, and we’d love to tell you all about it.

We are a group of six University of Washington students, pursuing degrees in Environmental Sciences, Environmental Studies, Ecological Restoration, and Landscape Architecture. This year we are taking part in a series of three “capstone” classes where we were assigned a location (Yesler Swamp) in need of restoration, analyzed the site, planned an approach to restoring the site, and then got to work! Along the way, we have completed dozens of tasks aimed at not only improving Yesler Swamp, but preparing us for future restoration work as well. From taking soil samples and identifying invasive species, to purchasing plants and hosting work parties, we’ve learned, first-hand, exactly what goes into a restoration project.


October, before restoration work began

Our work began in the fall, with a thorough analysis of the site, looking at the soil and hydrology, existing plant and animal species, slope, sunlight, human disturbances, and more. We gathered this information into a report to refer back to as needed. We then drafted a proposal for how we would remediate the site. Based off of the information we had gathered, we determined that our primary goal was to attempt to discourage and control the growth of three invasive species on the site: reed canarygrass (Phalaris arundinacea), purple loosestrife (Lythrum salicaria), and garden loosestrife (Lysimachia vulgaris). All three thrive in the sun, but especially the reed canarygrass, which is also the most abundant and invasive on the site. For this reason, our proposed method of control was to plant a variety of native species which would grow quickly to shade our the invasive species while also being able to tolerate the wet, swampy conditions. This turned out to be a greater challenge than anticipated! Our plan also included choosing species that would add bird habitat and aesthetic value to the site while preserving the view.

    
Reed canarygrass and loosestrife

The on-site work began during the cold, wet winter months. In January and February, we spent several weekends putting our plan into action. First, we removed as much invasive biomass from the site as possible. This included all of the tops and as many roots as possible from our targeted invasive species. Wheelbarrow after wheelbarrow load was taken away from the site to be composed. We then covered the areas most impacted by invasives with cardboard and a six-inch layer of soil (photos below). The intention was to smother and block out the light to prevent further growth of invasive species while also raising the level of the soil in an attempt to dry it out. We knew that the shrubs and trees that would later be planted on the site would appreciate having slightly drier conditions than what was existing. Last, we planted the site with over 500 native shrubs, small trees, herbaceous species, and grasses and sedges. All were carefully chosen for their tolerance of water, and other desirable qualities, such as blooms, berries, or interesting foliage.

    
Removal of invasives and addition of topsoil (and cardboard underneath)

  
Planting day!

This spring we are looking forward to the future of the site by considering what maintenance needs will arise. Will the restored site be successful? What will guarantee its success? These are some of the questions we have asked ourselves. Community involvement is the answer. Stay tuned to see how you can help. In the meantime, here are a few photos of our restoration process.

 

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