The Homeowners Column

The Homeowners Column

Rain Gardens are Practical and Beautiful

October 7, 2005

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

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 -

  • Reduce flooding, erosion and storm water system usage.
  • Protect local streams and lakes from storm water pollutants.
  • Increase the amount of water that infiltrates into the soil to recharge groundwater. Rain gardens allow about 30% more water to infiltrate compared to a comparable patch of lawn.
  • Provide beauty and wildlife habitat.

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.

  • Size should be about 1/3 the size of the area it is serving. Individual gutters and downspouts service only part of the roof. For example a roof area of 200 square feet would need a 70 square foot garden or 10-foot x 7-foot.
  • Select plants using one of the many brochures available. Good rain garden plants such as cardinal flower, Joe-pye weed, tall bellflower, great blue lobelia, ironweed, Culver's root, turtle head and blazing star are also good landscape plants. As with any garden, pick plants for your soil type and sun duration. You can also incorporate some non-native non-invasive pants such as daylily and Siberian iris.
  • Be sure to call JULIE 1-800-892-0123 to locate utility lines before digging.
  • Locate at least ten feet from house to eliminate seepage into house foundation.
  • Place on down slope of downspout or sump pump outlet. Slope should be less than 12%.
  • Garden should be perpendicular to flow of runoff.
  • Do not place directly over septic system.
  • Locate in full to partial sun.
  • Dig a depression 6 to 8 inches deep. Some areas may have to be deeper to make the garden level. Make a small berm on the down slope from the rain garden to lessen chance of overflow.
  • Direct sump pump water or downspout water to rain garden by burying a 4-inch black plastic drainpipe or digging a slight swale.
  • Plant plants and mulch with wood chips. Until established, keep plants watered.

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/

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