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A rain garden is a shallow depression in the ground, natural or man made, that is designed to hold rain that would otherwise turn into polluted runoff. According to studies, many of our natural water sources are polluted with runoff that comes from roofs, lawns, and driveways. While rainwater is filled with nutrients that are good for plants, it can become contaminated as it flows along dirty roadways or through storm drains.
With rain gardens, however, the rainwater soaks into the ground rather than running down streets or drains. Planting a rain garden not only helps keep water sources clean, but also benefits local wildlife, which are dependent on lakes, rivers, and streams for much of their drinking and food supply. Rain gardens are not expensive or difficult to maintain, though during periods of drought, watering may be necessary. In addition, a rain garden can be an attractive landscaping feature.
A rain garden is an easy garden design to construct and doesn’t take up a lot of space. The best time to design a rain garden is during heavy downpours. This makes it easier to determine what areas of the landscape receive the most rain, including drainage or runoff patterns. Most properties have an existing drainage pattern that can be used in creating a rain garden. Low-lying areas make the most suitable location for rain gardens. If no natural low-lying spots exist, simply dig one out.
A rain garden varies in depth, from 3-6 inches (7-15 cm.), and is dependent on its size and location. Rain gardens can be designed to accommodate nearly any type of gardening style in a variety of landscape settings. Rain gardens can even be added to existing buildings or other structures. Typically, rain gardens should be placed at least 10 feet (120 in.) away from foundations to prevent flooding problems.
While a rain garden is most often placed near a downspout to catch rainwater running from the roof, it can also be situated along a walkway or driveway to prevent runoff into these areas. Likewise, rain gardens can be tucked away into waterlogged areas along the side or back of the home as well. Backyard rain gardens are usually larger and can be integrated with existing gardens.
A rain garden must be able to absorb runoff water easily. Therefore, the soil should be amended with organic matter. Define the shape of the rain garden and select appropriate plants. While its design can take on nearly any appearance, the typical home rain garden is usually bowl-shaped. Native plants should be chosen for rain gardens, as they tend to be more adaptable. Plants in a rain garden should also be well suited to both wet and dry conditions.