How to Build a Rain Garden in Eugene, Oregon
How to Build a Rain Garden in Eugene, Oregon
Transform your yard into a sustainable drainage system that reduces stormwater runoff and filters pollutants before they reach Lane County's waterways.
What You'll Need
- Shovel and garden rake
- Hand trowel
- Wheelbarrow
- Soil percolation test kit or a 6-inch hole and water
- Native rain garden plants (sedges, rushes, and native wildflowers)
- Organic mulch (shredded bark or compost)
Steps
Step 1: Site Selection
Identify a natural low point in your yard where runoff collects, ensuring it is at least 10 feet away from your home's foundation. Avoid areas directly under power lines or over existing underground utility pipes.
Step 2: Percolation Testing
Dig a 6-inch wide hole and fill it with water to see how quickly it drains. In Eugene's varied clay-heavy soils, the water should drain within 24 hours; if it takes longer, you may need to amend the soil with sand or compost to improve infiltration.
Step 3: Mapping the Basin
Mark the perimeter of your garden using a garden hose or spray paint, typically creating a kidney or oval shape. Ensure the basin is wide enough to handle the volume of water from your downspouts or the specific area of runoff.
Step 4: Excavation
Dig out the soil to a depth of 6 to 12 inches, depending on your soil type. Pile the excavated soil on a tarp to use for berms or other landscaping projects, keeping the bottom of the basin relatively flat.
Step 5: Soil Amendment
If your soil is heavy clay, mix in a layer of coarse sand and organic compost to create a more permeable medium. This ensures that water filters through the soil rather than pooling on the surface for too long.
Step 6: Planting Native Species
Install native Oregon plants that can tolerate both saturated soil and periods of dryness. Place the most water-tolerant species, such as Slough Sedge or Red Osier Dogwood, in the deepest center of the basin.
Step 7: Mulching and Finishing
Apply a 2-to-3 inch layer of shredded hardwood mulch around the plants. This suppresses weeds, retains moisture during the dry Oregon summers, and prevents soil from eroding during heavy winter rains.
Expert Tips
- Use a 'diversion' or 'overflow' path to direct excess water away from the garden during extreme storm events.
- Avoid using synthetic fertilizers, as these can wash into the storm drains and counteract the garden's filtering purpose.
- Prioritize plants from the Eugene Saturday Market vendors or local nurseries to ensure they are acclimated to the Willamette Valley climate.