Articles

Roadside Guide to Clean Water: Rain Gardens

The adaptability of rain gardens makes it possible to fit them on urban and suburban sites where green space is limited.

Save for later Print

Updated:

April 29, 2025

Skip to the end of the images gallery

Photo by Andy Yencha

Skip to the beginning of the images gallery

Rain Gardens at a Glance

Rain gardens are shallowly depressed garden areas, usually less than 12 inches deep, planted with a mix of native plants, including flowers, grasses, shrubs, and trees. Most rain gardens are small, covering less than 500 square feet. They can be shaped like rectangles, ovals, crescents, and more. Some are long and narrow, while others are short and wide. Their adaptability makes it possible to fit them on urban and suburban sites where green space is limited. Home rain gardens typically collect stormwater from downspouts, driveways, and patios. City rain gardens receive runoff from streets, sidewalks, and parking lots. Urban rain gardens might also be called "bioretention practices" or "stormwater bumpouts."

How Rain Gardens Work

Rain gardens are sometimes described as being "bowl-shaped" because they are lower in elevation than the surrounding land. This shape allows stormwater to naturally flow down into them instead of into a nearby storm drain. Despite their name, rain gardens usually don't hold standing water for more than a day or so after it rains. They are meant to have porous soil that acts like a sponge and soaks up water quickly. Rain gardens capture stormwater runoff before it flows into storm drains, which in turn reduces flash flooding, protects streambanks from erosion, and recharges groundwater. Rain gardens are usually planted with native plants that further enhance the garden's ability to trap sediment, remove water pollutants, and provide habitat for songbirds, insect pollinators, and other wildlife.

Community Benefits of Rain Gardens

Stormwater: Reduces stormwater runoff
Groundwater: Recharges groundwater
Climate Change: Promotes climate change resiliency
Flooding: Mitigates flooding
Landscape: Beautifies the landscape
Pollution: Reduces pollution
Habitat: Provides wildlife habitat

You can expect to find rain gardens in urban and suburban settings.

How to Recognize Rain Gardens

Sidewalk drain into a small rain garden — Stormwater is sometimes directed to rain gardens from the street or sidewalks. Photo by Andy Yencha

Kidney-shaped rain garden with different kinds of vegetation — Rain gardens are bowl-shaped so that they can hold water during storms. Deep-rooted vegetation and the right soil mix encourage water infiltration. Photo by Andy Yencha

An enclosed rain garden with a stormwater drain running into it — Stormwater is sometimes carried to rain gardens by way of buried pipes or similar underground structures. Photo by Andy Yencha

A rain garden with standing water under construction next to a building — Rain gardens are often built in areas that naturally collect stormwater runoff, as illustrated by this rain garden under construction. Photo by Jodi Sulpizio

A mature rain garden blends in to the landscape — Finished rain gardens do not hold permanent water and blend in as landscape features. Photo by Jodi Sulpizio

The curb of this street includes cuts to allow water to enter the garden and drains — Stormwater can also enter rain gardens through cuts made in a street curb. Grated storm drains may be installed as a safety feature to manage overflow and prevent flooding during storms. Photo by Kristen Koch

Rain gardens and rain barrels are two of the most common water management practices used by homeowners. Learn more about rain barrels at "Rain Barrels in the Home Garden."