The Daily Southerner, Tarboro, NC

April 18, 2011

Planting a Rain Garden

Family Features
Family Features

The Daily Southerner — (Family Features) Storm water runoff can be a big problem during heavy thunderstorms. As the water rushes across roofs and driveways, it picks up oil and other pollutants. Municipal storm water treatment plants often can't handle the deluge of water, and in many locations the untreated water ends up in natural waterways. The EPA estimates as much as 70 percent of the pollution in our streams, rivers, and lakes is carried there by storm water.

To reduce the excess water runoff, many towns are encouraging businesses and homeowners to install rain gardens in their yards. Rain gardens are specially constructed gardens located in low areas of a yard where storm water can collect. The idea is to have the water naturally funnel to this garden. The rain garden collects water runoff and stores and filters it until it can be slowly absorbed by the soil.

Sizing Up a Rain Garden

The rain garden's size and location depends on the yard. If you're the type of person who likes precise measurements, there are guidelines you can follow for estimating the ideal size of a rain garden for your particular situation. For example, you'd want to measure the area of your roof that will be draining into the gutter leading to the rain garden, as well as the size of any paved areas that will be contributing to runoff into the garden. If your soil is sandy (which drains quickly), you'd want your rain garden to be about 20 to 30 percent of the area that will be draining into it (roof plus driveway, etc.) If you have clay soil, your ideal rain garden would be 60 percent of the drainage area. But don't let these numbers intimidate you - any size rain garden is better than none at all.

The ideal place for a rain garden is in a natural depression. You also can funnel water from downspouts or gutters into the garden. The soil should be well drained so the water doesn't sit in the garden for more than two days. A special rain garden soil mix of 50 to 60 percent sand, 20 to 30 percent topsoil, and 20 to 30 percent compost is recommended. You can dig this mixture into the soil to depth of 2 feet before planting.

Choosing Plants

The most difficult part of building a rain garden can be plant selection. The plants in a rain garden need to be tolerant of sitting in water now and then, so native plants and wildflowers are good choices because they're so adaptable. You probably already grow many of them - ferns, ornamental grasses, sedges, iris, milkweed, asters, and black-eyed Susans, to name a few. The idea is to create a naturalistic planting that's easy to maintain (no fertilizer needed) and welcoming to butterflies and bees and other creatures.

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A former floral designer and interior plantscaper, Kathy Bond-Borie has spent 20 years as a garden writer/editor, including her current role as Horticultural Editor for the National Gardening Association. She loves designing with plants, and spends more time playing in the garden - planting and trying new combinations - than sitting and appreciating it.