A rain garden is a type of bioretention, constructed as a shallow depression to hold and infiltrate water from rooftops via downspouts, driveways or other impervious surfaces to reduce polluted rainwater runoff.
Sizes and depths vary based on the amount of impervious surfaces and soil types, but typical residential rain garden sizes are 100-300 square feet and 4-8 inches deep.
Rain gardens are planted with native or well adapted plant species that can tolerate both wet and dry conditions and have deep roots that promote water infiltration. Water should drain completely within 24-48 hours.
Specific maintenance considerations include watering plants until well established in the first two years, annual weeding and mulching, and removing debris as needed from blocking water flow.
Rain gardens can be designed in a variety of ways to meet individual preferences as a landscaping feature for seasonal interest, wildlife habitat, color, and function.