What is a rain garden? A garden shaped into a bowl-like depression in the ground that is about 6 inches deep designed to capture rainfall runoff from your rooftop and driveway and allow water to filter into the ground. The plants, mulch and soil in a rain garden combine natural processes to filter pollutants from runoff and break down in the soil over time.

A rain garden helps improve water quality and prevent erosion. When rain falls on water-resistant surfaces, it creates runoff loaded with fertilizers leaching from what we put on our landscapes, motor oil from our cars and other pollutants. Consider whether your yard is a good location for a rain garden. Remember: gravity works.

The right place for a rain garden is usually downstream from a major water runoff source, such as a roof or road at the lowest elevation point on the property. Site analysis is one of the first steps in any design. For a rain garden application, be sure it’s situated away from building foundations, septic systems, well heads and utility lines. Partial to full sun is ideal, and be sure to call 811 to get underground utility lines marked before you settle on a spot – at least three business days before you dig.

If the water table is too high or the soil is too wet or impermeable, a rain garden won’t work, but a wetland garden might be a viable alternative. The Soil Survey of Lee County, NC compiled by the NC Dept of Natural Resources and Community Development, provides quite a bit of useful information including Table 15 – water management data regarding limitations for use and features affecting drainage for each soil type. The survey contains a soil map of the county so it is possible to locate your site on the map and what soil type you are dealing with.

Once you’ve determined that a rain garden will suit your needs based on the site analysis, it’s time to design the space to perform the functions you are looking for. The rain garden should be four to six inches deep (the center being the deepest). Use some of the extra soil to create a slight berm, which allows some water to be retained during rainfall. Then begin the plant selection process according to the performance and aesthetic criteria for your particular circumstances. Rain gardens are typically planted with shrubs and perennials (natives are ideal), and can be colorful, landscaped areas in your yard. The plants that tend to do well in rain gardens are ones that can tolerate wet conditions, but also very dry conditions. Just like any other living, growing plantscape, rain gardens will need some maintenance and care, but with careful selection with attention to sustainability characteristics, the rain garden can be low maintenance. There are plants that are not suited to a rain garden due to the characteristics like heavy fertility needs, susceptibility to root rots, or overly aggressive root system development.

It’s better to plant on the edge of the garden so that roots are higher than the lowest point of the garden, where water will pond. After planting, add mulch in order to prevent erosion and help in further water filtering. Be sure to cover the berm with mulch or grass as well.

Your North Carolina Cooperative Extension Agents can help identify plants for your situation. Read more.

Minda Daughtry is Horticulture Agent for N.C. Cooperative Extension in Lee County.