A rain garden is one designed to collect water runoff from the home's roof, paved area and other structures that do not absorb water. The ideal location of a rain garden is a depressed area in the yard where water naturally flows and absorbs within two to three hours. The size of the garden should be approximately 20 to 30 percent of the area the water is draining from. A typical rain garden is 100 to 300 square feet in size, but can be larger or smaller based on the available area.
Plan the location of the rain garden. Choose one that is a minimum of 10 feet from the house, has full sun to partial shade light conditions and a natural slope with at least a 1 percent grade. Stay away from septic systems, underground utilities and areas that are low and have standing water problems.
Estimate the area that will be supplying water to the rain garden. This includes the square feet of the roof draining to the downspout and paved areas providing runoff to the garden. Determine the type of soil in the rain garden area. Sandy soil gardens need to be 20 to 30 percent larger than the drain area and clay soil garden need to be 60 percent larger than the drain area.
Remove lawn sod from the rain garden location. Dig to remove the soil by creating a gradual slope to the edge of the garden like a trough. Make the deepest portion of the slope approximately 6 inches deep.
Direct the home downspout and sump pump outlets toward the rain garden to increase the amount of water flowing to the area. Create a natural slope or add underground drain tile if necessary.
Plant native species of plants in the rain garden as they are lower in maintenance and withstand harsh growing conditions. Place the same variety of plants in clumps of three to seven as it is more eye appealing. Mix native ornamental grass types with perennial wildflowers to create strong root structures that will prevent soil erosion.
Water the new plants every other day for two weeks after planting to stimulate root growth. Watering is not required once the root structures are established.
Apply 3 inches of mulch around the plants in the rain garden to hold moisture and limit weed growth.
Monitor the garden to make sure the plants are growing adequately. Move plants that are not performing well in their location.