Sustainable Landscaping Practices | Minnesota

Rain Garden Facts

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front yard rain garden in Minneapolis, Minnesota

Native plant material, a soil mixture that is optimal for filtration and absorption, and proper grading create a system that captures runoff and facilitates water uptake into the soil.

Rain barrels are often used to capture runoff and direct it into a rain garden.

Storm Water Runoff: A major source of water pollution

Minnesota’s most notable attraction is its ever-famous waterways, including streams, rivers, and lakes. We are truly lucky when it comes to the natural richness and beauty of our region. However, with each passing year, water pollution threatens the delicate ecological balance of our waterways. High levels of chemicals, nutrients, and sediment harm vegetation, kill wildlife, foul drinking water, and destroy pristine recreational areas.

Where does all this water pollution come from? Up to 70 percent of harmful pollutants are introduced by storm water runoff from local towns and municipalities.

Storm water runoff can be defined as unfiltered water that reaches streams, lakes, sounds, and oceans by means of flowing across impervious surfaces: roads, parking lots, driveways, and roofs.

Runoff deposits pollutants – sediment from development and new construction, oil, grease, toxic chemicals from vehicles, de-icing chemicals, and heavy metals – via storm drains and sewers into our lakes and streams. Lawn clippings and leaves are also washed into our waterways, reducing oxygen levels and ultimately suffocating fish and other aquatic species.

Rain gardens are a practical, beautiful landscape feature that can keep pollutants from reaching our precious waterways.

illustration of a rain garden

​Illustration Courtesy Iowa Natural Resources Conservation Service, CLICK TO ENLARGE.

Rain Gardens: Nature’s Filter

It just so happens that soil, along with being a life-supporting substance, also acts as a superb filtering system. Water becomes more or less cleaned, and toxins are neutralized when water passes through the soil. Basically, a rain garden is specifically designed to slow water down so it can be filtered by the soil.

A mini-wetland

Think of a rain garden as a scaled-down version of a wetland area. Native plant material, a soil mixture that is optimal for filtration and absorption, and proper grading create a system that facilitates water uptake into the soil.

Rain Garden Features

The features of a rain garden include a shallow basin with gentle side slopes (usually four to eight inches deep); soil that allows infiltration; and moisture-tolerant plants with deep roots to trap sediment. The basin temporarily traps the water, allowing the soil and plant material to work their cleansing magic. Soil should be porous enough to absorb water within 48 hours. This keeps the garden from becoming a breeding ground for mosquitoes. Native plants work best in rain gardens because they are uniquely adapted to live through extremes of moisture and temperature. And their long roots are helpful for water infiltration.

A Low Maintenance Habitat

A rain garden can be large or small, and almost any size or shape. Even a small rain garden can make a difference. Rain gardens require very little maintenance and provide attractive habitats for butterflies and birds. Annual cleanup and occasional weeding are all that’s required.

Rain Garden Tips

Plant Choices

Choose native plants based on their needs for light, moisture, and soil. Vary plant structure, height, and flower color.

Depth

A typical rain garden is between four and eight inches deep. This depth helps assure water will infiltrate quickly and not pool.

Size

A rain garden is typically 5 to 10 percent of the size of the impervious surface that generates runoff.

Soil Amendments

A good soil mix for rain gardens is 65 percent sand, 15 percent topsoil, and 25 percent compost.

Location

In order to do its work, a rain garden should be strategically located to intercept water that flows from gutters and downspouts and across paved surfaces such as driveways and walkways. A rain garden located under a downspout can capture thousands of gallons of water annually. Rain gardens are commonly located near alleys and driveways, in the low areas between houses, and in places where pools and puddles naturally occur.

Contact Us

For help designing and building a rain garden or green space that is beneficial for the environment, contact Southview Design.

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Southview Design is committed to healthy and sustainable landscaping practices.

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