Q: What is a rain garden and how can I create one? 

A: Rain gardens (unlike rock gardens) aren’t something you can pick up at your local home improvement store. But they are something you can create on your own with a little know-how.

Essentially, a rain garden is a shallow basin filled with native plants and shrubs designed to trap rainwater and ensure that is absorbed into the ground. How does it work? Rain is channeled from your roof via gutters, pipes or simply openings in the land to the basin, where the rain feeds the vegetation.

In concept, rain gardens have existed for years. The first rain gardens were purposefully created in 1990 by a developer named Dick Brinker in Prince George’s County, Md., in conjunction with Larry Coffman, the associate director of the Maryland Department of Environmental Resources. Together, they designed a rain garden on each of the residential properties in Brinker’s new development, which cost $300,000 less than it would have to build a traditional rainwater drainage and sewer system.

Etan Hindin, a watershed ambassador at the New Jersey Department of Environmental Protection, explains that the main objective of a rain garden is to assist with storm water management and to prevent water pollution. What currently happens is that during a storm, the water that lands on your roof goes into the gutter and out into a storm drain. “That water picks up whatever is in its path as it moves over the land, whether it be motor oil or pesticides, and gets washed, without being purified, into the nearest river, stream or lake,” Hindin tells MNN. The objective of a rain garden is to prevent that from happening, because the soil around your house can naturally purify the rainwater. From a functional perspective, rain gardens also help to prevent flooding in heavily paved areas where severe storms can cause major issues.

Hindin explains that in older towns in the U.S. with CSOs (combined sewer overflow systems), rain gardens have become even more important. CSOs are systems in which the sewer drains and storm drains combine underground into one network. “During a major storm, waste water treatment plants can’t keep up with the supply of storm water and you end up having raw sewage going out into the rivers and ocean, a disastrous result,” Hindin says.

Unlike a retention pond, effective rain gardens will absorb the water within 24 hours and will otherwise be dry.

So how do you build a rain garden? It’s all about location. The best thing to do is to look at the topography of your yard, preferably during a rainstorm. This way, you can see where water naturally flows and puddles and find a down-slope area that naturally receives water. You also don’t want to build a rain garden too close to your house, over a septic system, or away from all sunlight. Once you have the perfect area, the idea is to fill it with native species that will flourish in the rain garden without the aid of human maintenance. “In essence, this is the way it was before we built all of these impervious surfaces like roads, sidewalks and rooftops. Well, let’s hope your rooftop is impervious!” says Hindin. “Rain gardens help us to get the rain back where it belongs — in the soil.”

For more on rain gardens, check out the Rutgers Rain Garden website or search for your own state’s rain garden manual on the Web.

— Chanie

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Photo: Rutgers