What is a rain garden?
A rain garden is a shallow depression that is planted with native wetland or wet prairie wildflowers and grasses. Rain gardens are strategically located to capture runoff from impervious surfaces such as roofs, driveways, parking lots, and roads. These landscaping features help create beautiful green spaces while absorbing water, reducing runoff, protecting water quality and preventing flooding.
How does a rain garden work?
Rain gardens improve water quality by reducing and filtering runoff. The most polluted runoff occurs in the beginning of a rain shower as water rushes over hard surfaces. This water is the first to pick up sediments and pollutants. Rain gardens catch this water before it enters the storm drainage system. Sediments and pollutants settle out of the water and are absorbed by plant roots or treated through chemical processes in the soil.
Why use rain gardens?
The Nonpoint Source Work Group Executive Summary from the 2003 Iowa Water Summit says, "As a result of our landscape changes over time, storm water does not infiltrate into the soil as it once did. Storm water runs-off the landscape at an increased rate and volume, carrying with it the sediment, nutrients, and other compounds that constitute NPS pollution. More attention must be given to identifying technologies that reduce the amount of water and pollutants leaving the landscape."
Rain gardens -- depressed areas planted with hydrophilic native prairie plants -- address this very issue. Rain gardens help slow the flow of water over the surface of the landscape, and increase infiltration of water into the water table, all while filtering that water and reducing pollutants. The addition of rain gardens to our urban landscape could greatly reduce nonpoint source pollution in Iowa.
Rain Gardens can:
Help solve common drainage problems
Reduce runoff and recharge groundwater supplies
Keep sediments and pollutants out of streams
Attract birds and butterflies
Require less maintenance than grass lawns
Reduce the amount of water pollution
Rain Garden FAQ's
Q. Will a rain garden provide a breeding ground for mosquitoes?
A. No. A properly designed rain garden will drain before mosquitoes can reproduce. It takes 10 - 14 days for a a mosquito to develop from an egg into an adult. The rain gutters on your home are more likely to provide a better breeding ground than a rain garden.
Q. Do all rain gardens have a wild and messy appearance?
A. No. Rain gardens do have a natural rather than a manicured appearance, but they need not look messy. You can keep a rain garden looking neat and attractive by keeping the edges well defined. Taller plants often have a more unkempt appearance; so use shorter plants if you want your garden to have a cleaner look.
Q. Would a rain garden cause flooding in my basement?
A. Not if they are properly located and designed. Rain gardens should be located at least 10 feet away from buildings so that water does not drain along foundations. Also, your rain garden should drain away from rather than toward buildings.
Q. Would I need to water my rain garden during dry periods?
A. Maybe. How much water your rain garden needs will depend on the plants you choose. Native plants are adapted to a wide range of conditions, so they will only need watering in the driest seasons.
Rain Garden References
Please visit anyone of the following useful rain garden websites.
Gardening with Water Quality in Mind
University of Wisconsin Extension