Gardens are local. It?s not often that your home landscaping does much more than appease your spirit, please the neighbors and provide the occasional transcendent salad. All good things, of course, but the advent of specialty landscapes like prairie gardens and butterfly gardens have given people the chance to reconnect their backyard landscape to natural history.

A new gardening concept ? the rain garden ? also gives people a chance to improve lake quality and decrease the chance of neighborhood flooding. Rain gardens try to make up for the fact that your house got its start by disrupting nature?s garden. The average abode on a quarter-acre lot ? including sidewalk, driveway and the street out front ? increases run off by a factor of four, says Roger Bannerman, a DNR stormwater specialist.

After spending two decades studying other people?s run off, Bannerman took a small bequest from his Aunt Iris and constructed a 180-square-foot garden on his own lot (see above picture), on an intercept course between the downspout and the sidewalk. While a healthy lawn could probably absorb most of the water if it was well distributed, if you look closely, you?ll find that water from your downspout tends to follow a fairly narrow path to the sidewalk, then the storm sewer and finally the nearest lake.

?From my house, it goes on to Lake Wingra,? says Bannerman. As a scientist and a neighborhood advocate, he has watched that lake slowly degrading, getting saltier and filling with sand where the storm sewers enter. ?We?re essentially enhancing the infiltration that?s already occurring by providing a place where the water has to stop and then go down,? says Bannerman of his garden. ?Every storm that has occurred, the rain garden has been able to hold its own. The water doesn?t leave the site. I figure that roughly, in one year, it controlled about 10,000 gallons of water.? It?s a double benefit: the less dirty water going into lake via storm sewer, the more clean water enters via groundwater channels.

To corral the rain, he dug a three-inch depression, then used that soil as a surrounding berm. Bannerman?s small garden includes 10 different prairie species. He put in one plant for each square foot, then just watched it fill in. ?It?s been relatively low maintenance,? he says. ?I had some weeds in the beginning to hoe, but now that the prairie plants have taken hold, weeding has become very minimal. The garden is very robust and has a tremendous floral display.?

It?s going to be a busy spring for Bannerman. He?s planning two more rain gardens to deal with the remainder of his roof catchment, and he?s working on a manual to provide local homeowners with advice on how to build a rain garden. While they?re not difficult to construct, there are a few important technical issues: what kind of soil and topography is needed, how big and how far from your house and what plants work best. The manual will be available through UW Extension?s Web site ? www1.wuex.edu.

Erik Ness is Madison Magazine?s senior environmental writer.