When it storms, it shines brightly

Rain garden saves water and provides lush plantings

In the Garden

August 01, 2004|By Denise Cowie | Denise Cowie,KNIGHT RIDDER/TRIBUNE

So you looked out the window after a thunderstorm and saw water pooling in your lawn, not running off into the gutter.

Did you tsk-tsk and resolve to fill the depression with topsoil first chance you got? Or did you see it as an invitation to install a rain garden?

If you chose the rain garden, take a bow. Not only will you have an attractive landscape feature, but you'll be doing your bit to cut down on water pollution, slow the rate of stream flooding in developed areas, and replenish groundwater.

Although the concept is as old as nature itself, rain gardens are shaping up as one of the newest trends.

"I think this is something that is hot, something that definitely is capturing a lot of interest," says Nancy Beaubaire of Bowman's Hill Wildflower Preserve in Bucks County, Pa., north of Philadelphia. The preserve has held a workshop on rain gardening.

"It is fairly new to gardeners ... but it has been gaining increased recognition in the last few years," says Dan Welker, an environmental protection specialist in the U.S. Environmental Protection Agency's regional office in Philadelphia.

Just what is a rain garden?

"To me, it is simply gardening in a natural or man-made depression," says Welker, who has created a Web site on green landscaping (www.epa.gov/reg3esd1/garden). "It can be any shape, and as formal or as naturalistic as you like, but the purpose is to slow down and trap runoff after rain," so less storm water is channeled into streams ill-equipped to handle it.

Instead of running off driveways and other impervious surfaces into gutters and storm drains, rain is captured in shallow depressions, or a series of them, planted with ground covers, perennials, shrubs, even trees. As the rainwater slowly seeps through mulch and soil layers, Welker says, pollutants are filtered out, broken down through chemical processes, or absorbed by plants, so that what percolates down to recharge underground wells, springs, and feeder streams is cleaner.

Diverting runoff

Welker knows the benefits firsthand: He has turned the back yard of his Chestnut Hill, Pa., home into a lushly planted rain garden that is a magnet for songbirds, frogs, toads and other wildlife. Even the deck is designed to allow rainfall to drain through into the garden.

"I created the rain garden even before I was really aware of this whole [runoff] issue," he says. "It has been a fun education process," but it has made him increasingly aware of the impact residential landscapes have on the natural world.

Historically, we've tended to look at storm water as a negative, Welker says. "The idea was to get it off your property as quickly as possible. We even graded lots to get rid of it."

Trouble is, rapid runoff sweeps everything along with it - pesticides and fertilizers from our gardens and lawns, animal waste and oils and other toxins from streets and gutters. The volume of water can rip out stream banks, cause water levels to rise and fall rapidly, and stir up sediment, which can not only smother stream creatures but cause water to heat up.

"It kind of goes on and on, a vicious cycle," Welker says. "And we can attribute some of that to the way we cover the land around our houses. We don't think much about it - if it's a new house, we cover most of it with grass. We don't think in terms of trying to re-create a forest, or a wildflower meadow, or many of these more natural environments that would mimic nature ... and be much better at slowing the water down."

More than half the surface in any suburban area is turf, he adds. "Turf is better than being paved over, but compared to a richer gardening style, it also speeds up the runoff, because the roots for lawns are very shallow, and the soil is compacted, so it doesn't soak in much."

Rich in plants

There's not a blade of grass in Welker's yard. Right after he bought the house in 1987, he removed the lawn that covered most of the back yard. To create the peaceful urban oasis he envisioned in its place, he first transformed the uninspiring rear of the house by adding a light-filled sitting room with French doors opening onto a large, low deck.

Within a year, he installed a pond, now home to a hardy water lily and a few goldfish for color, as well as some small native fish rescued years ago from a drought-stricken stream.

Later, he added a naturalistic little waterfall, and a bog garden adjacent to the pond, to accommodate sundews, pitcher plants, horsetail rush and bog iris, and recontoured the rest of the yard into large, shallow bowls divided by a ridge.

More than 100 species of plants grow in his garden, which is less than 40 feet wide and about 50 feet deep. About two-thirds are native plants.

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