Rain gardens are in full bloom. The natural beauty and practical benefit of a rain garden makes it a popular choice for home landscapers who want to do their part to improve water quality. Many people do not realize that rain carries pollutants from our yards, streets, sidewalks and parking lots to the nearest storm drain which leads directly to local lakes, streams and rivers. Rain gardens are designed to have a center depression to help rainwater seep into the soil. This infiltration helps recharge groundwater and reduces polluted runoff.
Planning a rain garden
You will need to evaluate several factors including: soil type, the presence of underground utilities, degree of slope, size of drainage area, and existing structures on your property. First, determine the drainage area where existing runoff flows from roof downspouts, paved surfaces, or compacted areas of the lawn. Next, calculate the area of all runoff surfaces that will collect in the rain garden. The rain garden should only be about 10% of the size of the area contributing to the runoff. The rain garden should also be about 6-10’ deep. Soils can vary greatly in their drainage capacity, so try to position the garden in an area where the soil is rich, crumbly and well-drained. Your garden should be about 10-15 ft. away from any structure foundation in an area with no more than a 10% slope. A greater slope will require excess digging to create a level bottom in the garden. Finally, use an extension from your roof downspout, drain tile, or stones to direct runoff into the rain garden.
Planting a rain garden
When selecting plants for your garden choose from the broad palette of Minnesota native plants listed on this page. Include at least half grasses or sedges which provide dense rooting and support for the stalks of flowering plants. The fluctuation of water levels in a rain garden makes plant selection important. The soil will retain the greatest amount of moisture at the center of your garden and should be planted with species adapted to wet soils. Dry-soil dwellers can be placed at the edge of the garden.
Native plants are adapted to soil and light conditions in Minnesota. They will thrive without fertilizers and pesticides. These native plants also have elaborate root systems that create channels in the soil causing it to readily absorb water. The traditional turfgrass lawn tends to be a less permeable surface and have a higher environmental impact. Rain gardens will also attract new friends. Not only will neighbors admire the vibrant health of a well-designed garden, but also wildlife such as birds, butterflies and beneficial insects will become more at home in your yard.
For detailed information and instructions on planning the design and implementation of your rain garden, visit the following web sites. To find a local landscaper to install a rain garden for you, visit the Minnesota GREEN PAGES directory under Gardening.
Garden planning and design:
- Rain Gardens: A How-To Manual for Homeowners, cecommerce.uwex.edu (Search for Stock #GWQ037)
- Rice Creek Watershed District, Rain Garden Design Details – www.ricecreekwd.com/bmp/rg
Financial & Technical Assistance:
- Minneapolis Blooms (Minneapolis City Residents) – www.minneapolisblooms.org/brochure_raingardens.htm
- Ramsey Conservation District (Ramsey County Residents) – www.ramseyconservation.org – (go to NATURE program)