How much do you like your lawn? A lot? A little? Do you groom it to a golf-course green and glow with pride when your neighbors turn almost as green with envy, or do you hate every precious minute it takes to mow the stuff?

However strongly you feel one way or the other, Zora Lathan of the Chesapeake Ecology Center would like you to please, for the good of the planet, reduce huge expanses of turf.

"Lawns are up to 90 percent impervious," Lathan said. "Most people don't realize that." Impervious spaces -- not just lawns, but buildings, driveways, parking lots, streets and highways -- fail to catch and hold rainwater. Instead, the water simply runs off, carrying with it any contaminants or pollutants (gasoline, fertilizer, pesticides) and filling storm sewers or swelling streams, which in turn pour potentially deadly water down through watersheds and into bodies of water such as the Chesapeake Bay.

"Any water that falls on your land should stay," Lathan said. That doesn't mean it simply sits there. Water should slowly percolate into the ground, becoming cleaned and purified, then replenish the aquifer, the water-holding layer that is the source of well water. Water that runs off never gets to the aquifer, and it never gets cleaned of chemicals that can lead to reduced oxygen in bodies of water, such as the Chesapeake Bay, endangering fish, crabs and other forms of life.

At the end of August, a report by the University of Maryland Center for Environmental Science said that the oxygen-depleted "dead zone" covered 41 percent of the bay estuary. That was up from 36 percent in July, making it one of the worst months in more than two decades.

While some of the pollution that's causing oxygen levels to drop comes from farms and commercial operations that aren't under the control of ordinary people, every bit of effort to stop runoff is important, Lathan said. "We need better landscaping processes, or we will pay a price. You may not care about the environment from a landscaping perspective, but you do care about what's on your dinner plate."

Lathan is executive director of the Chesapeake Ecology Center, a nonprofit environmental organization that runs 18 native plant demonstration gardens on the grounds of Adams Academy at Adams Park in Annapolis. The academy is an alternative school for at-risk middle students, and part of the curriculum is working in the gardens.

Some of the kids are reluctant at first to embrace gardening, Lathan said, but when they see the results, they end up being proud of their work.

Volunteers also help at the gardens. A recent project has been removing asphalt from swales designed to funnel runoff from the school's parking lots into a nearby stream. Now we know there are better ways to handle runoff than building drainage culverts. The swales will be turned into "rain gardens," planted areas where water will not run off, but will be absorbed into the soil.

Creating a rain garden is one of things people can do to improve their immediate environment. Lathan is always surprised that people think it difficult. A rain garden is no more than a 3- to 6-inch, saucer-shaped depression planted with native grasses and flowering perennials. The depression and the plants collect rain and let it seep into the earth. The depression shouldn't be so deep that water pools -- it should be gone in 24 to 48 hours.

And the area needn't be large. "Any size rain garden is better than no rain garden," Lathan said.

Good plants for a native rain garden are switchgrass (Panicum virgatum), smooth white penstemon (P. digitalis), silky dogwood (Cornus amomum), arrowwood viburnum (V. dentatum), spicebush (Lindera benzoin), cinnamon fern (Osmunda cinnamomea) and big blue lobelia (Lobelia siphilitica).

What you don't want to plant, and what you do want to do away with if you have them in your yard or garden, might be the invasive non-native plants, such as butterfly bush, miscanthus, Bradford pears or English ivy. These plants, while beautiful and popular, crowd out native species and often are useless to native fauna, providing neither habitat nor nourishment.

When explaining the invasive non-natives to students, Lathan uses the example of the northern snakehead, the voracious Asian fish that devours other fish and aquatic life in its environment. It destroys native species.

There are a growing number of places to get information on rain gardens. See what's being done locally on the Pepco Rain Garden Installation Site at www.potomacriver.org/arbc/rgphotos.htm. Many nurseries and garden centers carry selections of plants suitable for planting in rain gardens.

Another landscaping process that helps retain water and nurture native species is to create contours in the garden. Contours, except for gentle slopes, are not lawn mower friendly, but nature is all about knolls and swales, Lathan says. These topographical changes are what make it possible for plants to grow on their own without need for special care such as fertilizer and irrigation. This type of water-efficient landscaping is frequently called xeriscaping.

Although xeriscaping has most notably taken hold in the desert Southwest, it can actually be practiced anywhere. It simply means gardening in a water-efficient manner, using mulch and compost to hold moisture and installing more native plants that will withstand the typical rainfall received in a particular region. They don't need to be watered or fertilized. Xeriscaped knolls work well with rain garden swales and create a natural landscape that offers living places and food for birds, insects, and other wildlife.

To learn more about rain gardens, native and non-native plants, and other Bay-friendly landscape techniques, visit the Chesapeake Ecology Center's Garden Open House, book release and native plant sale from 10 a.m. to 2 p.m. on Saturday, Sept. 17, at the Adams Academy at Adams Park, 245 Clay St., Annapolis.

There will be guided tours of the 18 demonstration gardens, children's activities and refreshments. In addition, Lathan and Thistle A. Cone, authors of "Ecoscaping Back to the Future: Restoring Chesapeake Landscapes," are to autograph copies of the book. It has nearly 100 pages of practical, up-to-date information on conservation landscaping, including a list of resources for plants and information. The book costs $15 and benefits the ecology center, which depends on donations, volunteers and fundraising efforts for survival. For more information and directions, go to www.ChesapeakeEcologyCenter.org.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.