By Mary Gilbertson, PWD
These Rain Garden downloads are courtesy of Wendy Garland at Maine DEP:
Rain Garden Information (pdf 68 kb)
Shady Rain Garden (pdf 295kb)
Sunny Rain Garden (pdf 539 kb)
When it rains, we usually think about it, if we think about it at all, like the children’s saying – rain, rain go away. But we don’t often think about what that really means.
Where, exactly, is “away?”
Roofs, parking lots, driveways, and roads are all structures that prevent rain water from soaking into the ground. That water becomes stormwater runoff. Stormwater runoff picks up fertilizers, soil, oil, and other pollutants and carries them to our streams, rivers, and lakes. On top of all this, running water is hungry water, and stormwater erodes our soils.
Here’s one reason why we have this problem: When people build houses they design them to get rid of water as quickly as possible. We use the principle of collecting water, concentrating the flow, and conveying it quickly off the property.
Did you know that during a 1 inch rainstorm, about 500 gallons of water runs off a typical roof? Where does this go? You guessed it – it becomes stormwater runoff, and can carry pollutants to our lakes and streams.
The good news is, we can all do things on our own property to reduce the cumulative impact of stormwater runoff. And one solution, elegant in its simplicity is a rain garden. A rain garden is a slightly depressed garden full of native plants where rainwater and snowmelt can soak into the ground, replenishing groundwater and protecting our surface water.
Rain gardens are easy and inexpensive to install and maintain. They are flexible in size, shape and appearance, and can fit in almost any landscape and lifestyle.
A rain garden is typically 1/3 the size of the drainage area, and bowl shaped with a center 4-8 inches deeper than the surrounding area. More water loving plants are placed in the center lowest portion of the rain garden, and more dry-tolerant plants around the edges.
Ideally, native perennials and shrubs should be used. Native plants are going to survive better in our environment, and do not require excessive fertilizer or pesticides. Furthermore, the roots of native perennials and shrubs extend down a few feet into the soil, while turf grass roots only grow down the same depth as the plant leaves are allowed to grow tall--just a few inches.
Maintenance is low, about the same as for any non-native perennial garden: they need to be weeded when young and watered until the plants are established.
The volume of water prevented from becoming runoff is impressive. For example, the rain garden installed in June at the Portland Water District returned roughly 11,183 gallons of water back to groundwater between July and December 2005. Not bad for one of the rainiest Octobers on record!
Visiting existing rain gardens can give you an idea of the diversity of possibilities that exist. Rain gardens have been installed throughout the state – contact your local Soil and Water Conservation District, the University of Maine Cooperative Extension, the DEP, or the Portland Water District to find a rain garden near you. Of course, I encourage each of you to visit the Portland Water District’s Sebago Lake Ecology Center to see our demonstration rain garden, along with other methods of reducing runoff at home.
The PWD and the UMCE are collaborating on a rain garden publication specific to Maine that will be available this spring. Meanwhile, check out http://www.raingardens.org and http://www.dnr.state.wi.us/runoff/rg/.
Hopefully this encourages you to plant a rain garden! It is one thing that each of us can do to help protect our surface waters, replenish our groundwater, and add some beauty around our homes. It’s not so overwhelming when you realize that each one of us can make a difference. A lot of little actions really do add up to lot in terms of protecting the health of our lakes!
Editor’s note: For extra help on landscaping, watch this source: NEW EXTENSION PUBLICATION Have you ever wondered how professionals design landscapes? Learn the basics of developing a base map, site analysis, and bubble diagram for your property. Includes tips on keeping your plan Maine-friendly! 8 pages, 2005. This fact sheet is available through Extension's online publications store at http://extensionpubs.umext.maine.edu/, by calling 207-581-3792, or by e-mailing us .