Rain Gardens Washington DC

Building a Rain Garden

Your rain garden should be located at least 10 feet from your home in a low spot where water naturally collects. It should have at least one-half day of sun and a gentle slope leading from your roof downspout, driveway or walkway to the garden. You can create a low swale from the roof downspout to the rain garden to ensure that water drains into the garden.

To build the rain garden, mark out a 150- to 450-sq.-ft. area, depending on the size of your house and amount of paved areas. Remove the sod and dig a shallow depression about 6 inches deep. Use the soil to form a berm on the lowest side of the garden to retain water. A 6-inch-deep rain garden should drain water within 7 hours. If the rain garden is deeper, the water may stay longer, creating a mosquito-breeding site.

Rain Garden Plants

Select regionally adapted plants that can withstand periodic flooding and offer seasonal color and interest. When fully planted, your rain garden will look like any other flower garden in your yard. Plant in clumps of at least three of each particular plant, and include ornamental grasses and sedges for texture and to help prevent soil erosion. Create a special “rain garden” soil mix of 50% to 60% sand, 20% to 30% topsoil, and 20% to 30% compost. Dig this mixture into the soil to a depth of 2 feet before planting.

The native plants you grow will depend on where you live. Some examples are swamp milkweed (Asclepias incarnata), queen of the prairie (Filipendula rubra), marsh marigold (Caltha leptosepala), columbine (Aquilegia formosa ), maidenhair fern (Adiantum pedatum), Joe-Pye weed (Eupatorium maculatum) and turtlehead (Chelone lyonii).

After planting, keep the plants moist, well weeded and mulched with shredded hardwood bark. (Bark chips and nuggets will float away during heavy rains.) Your rain garden will not only help reduce water pollution, but will also be an inviting place for butterflies, bees and birds to vis...