Extension Educator, Horticulture
This year rain was on our minds - either too much or too little. Except for the occasional rain dance we can't do much about where the rain falls, but we can do a great deal in determining where the rain goes. Have you ever looked out the window of a plane as it lands and noticed just how many hard surfaces you see? There are rooftops, driveways, streets, sidewalks and massive parking lots. When we pave and roof we take areas that use to be sieves for rainwater and turn them into funnels. Just watch your downspouts even with a light rain. The water gushes out. We love not having to slop around in mud, but by creating hard surfaces we change the flow of rainwater. Rain gardens are one solution to turn areas back into sieves.
Basically rain gardens are miniature temporary wetlands planted with native plants. Water from down spouts or sump pumps are directed into these depressions to allow the water to slowly infiltrate into the soil.
Rain gardens -
Rain gardens are not ponds. They are not designed to hold water permanently. Instead they fill after a rain and water slowly infiltrates into the soil over a couple of hours. The area dries between rains eliminating problems with mosquitoes. Mosquitoes are much more likely to occur in bird baths, storm sewers, tires and kiddy pools than in rain gardens. If during heavy rains the water stays longer than a couple days, just use "mosquito dunks" which contain a safe bacterial agent that kills only mosquito larvae.
Making a rain garden is pretty easy.
An excellent 32 page booklet entitled Rain Gardens – A how-to manual for homeowners by the Wisconsin Department of Natural Resources and the University of Wisconsin Extension is available at http://clean-water.uwex.edu/pubs/pdf/home.rgmanual.pdf
Useful information is also available at Illinois Rain Garden Initiative http://www.raingarden.il.gov/