Rain Garden Facts and Fiction: What a Rain Garden Is and Is Not

A "Rain Garden" is a fairly simple landscaping arrangement that is a vegetated depression where rainwater temporarily ponds. Usually simple enough to design and install without specialized technical expertise, rain gardens are simply low-lying, vegetated depressions—generally 3 to 6 inches deep—which have absorbent soils that temporarily collect stormwater runoff from impervious surfaces and allow the runoff to slowly percolate into the soil—usually with a few hours to 48 hours. A rain garden is not a pond or a wetland; nor is it a complex "Bioretention Installation."

Although a rain garden is a type of bioretention planting arrangement, a bioretention installation generally refers to an installation that is more sophisticated than a rain garden, and is designed/engineered by a landscape architect or an engineer. Complex bioretention installations are designed to mitigate larger amounts of runoff. They are typically deeper than rain gardens and incorporate underdrains.