Just three years ago, the term “rain garden” was foreign to me. Not anymore.

I first heard it at the International Master Gardeners Conference in 2007. Now it is a term that is the subject of a book, “Rain Gardening in the South: Ecologically Designed Gardens for Drought, Deluge and Everything in Between.”

A rain garden is designed to capture rain runoff in your yard, store the water to nurture its plants and cleanse runoff, removing the pollutants it carries with it, authors Helen Kraus and Anne Spafford write. Both authors are horticulturists interested in environmentally responsible gardening practices and professors who teach respectively at North Carolina State University and the University of Illinois.

The concept is gaining momentum around the world as communities commit resources to establish more environmentally friendly landscapes. Home gardeners can do the same.

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The book

“Rain Gardening in the South: Ecologically Designed Gardens for Drought, Deluge and Everything in Between,” produced by Eno Publishers, is available locally at Lorelei Books on Washington Street for $19.95.

All of us learned about the water cycle in school: Gentle rains hit the soil, seep to the roots of plants and trees and the excess flows into pristine streams that flow into rivers and then oceans.

That’s not so anymore, the authors say. Instead, rainfall collects oil and pollutants from roads and rooftops, then combines with soil and fertilizer to create contaminated runoff that flows into municipal storm water collection systems. Some is directed into wastewater treatment systems where it is treated before returning to the environment, but a considerable amount flows directly into streams and waterways. Rain gardens can intercept polluted runoff, clean it and allow it to filter down into our water reserves.

Rain gardens are easy and inexpensive to create, the authors say. First, a depressed area is developed either by berming a sloped area or by digging down 3 to 6 inches and piling the excavated soil around the perimeter. The depression should be deep enough to capture a significant amount of rainfall runoff but not too deep. An overflow area nearby, which can be planted in groundcover or made from rocks, is also a good idea to prevent soil erosion.

Soil composition in a rain garden is one of the most important factors for success. Compost or other organic material needs to be incorporated liberally into the soil 6 to 12 inches deep with 2 inches of organic mulch on top. This creates the filter bed, which allows the area to drain quickly. Without organic amendments, the depressed garden area might act more like a small pond breeding mosquitoes and water-logging the plantings. Organic material always fosters a healthy soil rich in microscopic organisms and earthworms.

Not all plants function well in a rain garden. The best choices will be able to assist in removing pollutants, slow water flow as it moves across the area and into the soil, support wildlife and be attractive landscaping able to tolerate drought or wet conditions. The authors present an entire chapter on suitable plants. Many are natives but some are non-native common landscaping plants. Their suggestions are broken down by shade tolerant and sun lovers as well.

Rocks often are incorporated to add beauty and to slow the water flow, allowing more water to penetrate the soil. They look particularly good with some of their recommended ornamental grasses.

To be effective as a pollution filter, a rain garden should be 5 percent to 10 percent of the impervious (driveways and rooftop, etc) area that drains into it. The garden depth is determined by the soil composition, the amount of water that needs to be captured in the area and the budget and energy level of the gardener constructing the project. It requires a little math to figure out exactly what size rain garden will be most effective, and the authors provide a table for those of us who are mathematically challenged.

A chapter is devoted to troubleshooting problems such as poor drainage, too much drainage with plants dying, erosion and mushroom invasion.

With so much emphasis on the environment these days, this book should be of interest to many Southern gardeners.

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Miriam Jabour, a Master Gardener and Master Flower Show judge, has been active in the Openwood Plantation Garden Club for over 35 years. Write to her at 1114 Windy Lake Drive, Vicksburg, MS 39183.