Rain gardens

Learn more about rain gardens and where they can be used.

How do rain gardens work?

A rain garden is a shallow depression in the ground that allows stormwater to slowly infiltrate the soil.  Native plants, mulch and soil in rain gardens naturally remove pollutants in the stormwater. Rain gardens receive stormwater from hard surfaces such as rooftops, sidewalks, driveways and patios, reducing the amount of stormwater (and pollutants) from entering our lakes, creeks and the Mississippi River.  

Polluted runoff is a big problem in urban areas where it is hard for stormwater to soak into the hard ground. Rainwater flows faster over hard surfaces, picking up pollutants before entering storm drains and the waters of Minneapolis.

Rain gardens are shallow depressions in the ground, and they can be simple or complex. They typically contain hardy and deep-rooted native plants, drawing water into the soil, helping to prevent stormwater runoff.

Frequently asked questions

What is a rain garden?

A rain garden is an attractive garden with a special purpose — to reduce the amount of rain water and pollutants entering streams, rivers and lakes. A rain garden is a place to direct the rain from your roof or driveway, and more importantly to retain that rain onsite instead of discharging to the storm drain system. Rain gardens are typically landscaped with plant species native to our region that can survive varying wet and dry conditions, that have deep roots to improve soil conditions, and that add beauty.

Why a rain garden?

Stormwater carries pollution from yards, streets, and parking lots into the nearest body of water. One study showed that up to 50% of that pollution comes from things we do in our yards and gardens! Creating a rain garden on your property can improve water quality in streams, rivers, and lakes in Minneapolis. You can use rain the way nature intended, instead of throwing this resource away. A rain garden is a natural way for you to help solve stormwater pollution problems, help recharge groundwater, protect our water resources, reduce beach closures and provide improved habitat areas for wildlife.

What makes a rain garden different from any other perennial garden?

A rain garden is bowl or saucer shaped, not mounded or flat like other perennial gardens. It is not just a pretty garden; it is designed with deep, loose soil, specifically to collect and absorb rain that would otherwise run off your property, and/or to solve wet spot problems where water is already collecting.

How long does water stay in a rain garden?

If designed and installed correctly, rain gardens typically do not have standing water for more than 48 hours. Be sure to test the soil type and infiltration rate, or percolation rate, before beginning your rain garden. Rain gardens may not be appropriate for all locations in Minneapolis – high water tables, clay soils and bedrock locations may inhibit the infiltration.

Are rain gardens breeding areas for mosquitoes?

To reproduce, mosquitoes require a number of days of standing water. There is rarely standing water long enough in a well-designed rain garden to allow mosquitoes to reproduce. In fact, rain gutters on homes are much more likely to produce mosquitoes than a rainwater garden.

Can the water in rain gardens be a hazard for small children?

During storms rain gardens can fill with standing water but this is typically no more than 18”. This water will begin to recede immediately after the rain has stopped, emptying in a matter of minutes or hours.

What happens to the plants when we have a dry period?

Native plants can live and thrive in a range of weather conditions, providing deep root structures. Those that are used to having their “toes” wet are placed in the lowest part of the garden and can withstand wet and some dry periods. Plants that like drier soil are placed on the banks of the garden and can withstand some wet and very dry conditions.

How large must a rain garden be to work?

Rain gardens should be designed to be able to completely infiltrate all of the water that flows into them within 24 hours. Any water that stays onsite instead of running into a storm drain or toward our lakes, river and creeks helps water quality. Rain gardens of any size will have a positive impact.

Additional resources

Metro Blooms - Promotes and educates gardeners, landscapers, community and businesses.  Metro Blooms also holds rain garden workshops in Minneapolis.

Clean Water Minnesota - Minnesota Water - Let's Keep It Clean

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