Rain Gardens

Rain gardens capture runoff from medium to large storms. They can be used to help solve drainage problems and reduce runoff from your yard. A rain garden is typically built to be 6-12 inches deep to collect and absorb rainwater. Mulch and plants slow down runoff and remove pollutants before the water reaches a storm drain. A typical rain garden is designed to collect and filter the first one-half to 1 inch of rain.

Learn more about rain gardens by watching this Rain Gardens for Homeowners webinar.

Benefits of a Rain Garden

• Get a credit on your stormwater utility fee for new or existing rain gardens! 
• Improved water quality by filtering out nutrients from stormwater that runs off your driveway or roof.
• A unique landscaping feature that’s relatively low maintenance.
• Tendency to be pest- and disease-free relative to conventional landscapes.
• A habitat for birds and butterflies.

Cross section of a typical rain garden

Installation

1. Select the location and size. The size is based on the amount of water that will drain to the garden. The location should be at least 10 feet from your home’s foundation, in an area with good drainage, and not under any trees. Rain gardens should be strategically located to intercept water runoff.
2. Loosen the soil and dig out a low depression at the rain garden location. Some soil may be removed, or existing soil can be amended with leaf mulch. The surface of the rain garden should be slightly lower than the surrounding area, so there is 6 to 12 inches of ponding depth in the garden.
3. Test your rain garden by observing it in a rainstorm before planting. Does the water soak into the soil following the storm within 48 hours? If it does, you are ready to plant. A properly designed rain garden will not retain water long enough for mosquito reproduction. Mosquitoes require seven days to complete their life cycle in standing water. If water remains for more than two days in your rain garden, the soil may be compacted or have high clay content. These problems can be remedied by loosening the soil and adding humus or mulch in the upper 6 to 18 inches of soil.
4. Select and plant appropriate native plants in your rain garden.

Maintenance

For the first year after the garden is installed, you may need to water the new plants if it doesn’t rain for an extended period of time. Once the native plants are established, they should be able to survive dry periods. Adding leaf mulch one to two times per year will nourish the plants and minimize the growth of weeds.

Rain gardens often thrive without the addition of fertilizers or pesticides because the native plants are well-suited for this area. Remove any weeds that do appear in the rain garden by hand-pulling.

Rain Garden at The Arlington