Over the past two decades, homeowners in arid parts of the United States have been quietly yanking out their thirsty Kentucky bluegrass lawns, replacing them with drought-tolerant turf such as tall fescue and buffalo grass, and surrounding them with stands of poppies, bellflowers, and bee balm whose lushness and color belie their scant need for water. It's part of a movement called xeriscape, from xeri—the Greek word for dry.

Xeriscaping—conserving water through creative landscaping—is a two-decade-old concept that grew out of concern for dwindling water supplies in the Front Range of the Rocky Mountains, where more than 50 percent of public utilities' water was being used to maintain landscapes. Nancy Leavitt, an environmental planner with the Denver Water Department, coined the term in the 1981. It didn't take long for the landscape industry to spread the concept nationwide through demonstration gardens, most of them sponsored by local water utilities and botanical gardens. Still, xeriscaping has had a public relations problem to overcome.

Some municipalities are asking homeowners and builders to install landscapes that conform to the climate and the local water supply. Photo: Denver Water Developed for the desert, it conjures images of parched rock-and-cactus gardens, but nothing could be further from the truth. Rather than a style of gardening, it's simply a way of designing that groups together plants with similar moisture needs, eliminating the potential for overwatering. The idea isn't to use no water at all, but through proper site and planting design, to use it sparingly. Some experts prefer the term water-smart gardening, an idea that's appropriate for all regions and climates. But by any name, the ethic is changing the face of landscapes across America.

Manipulating the Land. Denver landscape architect Ken Ball, who helped bring xeriscaping to national attention, says the single most important thing builders can do to get their client's property xeriscape-ready is to provide a decent soil base after the ravages of construction. At the start of the job, the native topsoil should be skimmed off and piled up separately, so that it can be worked into the landscaping later. And after the backhoes and cement trucks have left the site for good, Ball recommends bringing in a tractor to rip up the soil to a depth of 8 to 12 inches and tilling in organic matter—3 cubic yards per 1,000 square feet. “After months of heavy equipment being moved around, clay soil can be compacted into a consistency almost equivalent to a driveway,” Ball says. “When plants are put into all that horrible soil, most are doomed.” Another service that builders can offer clients is to take three or four soil samples and send them to the local cooperative extension service for analysis and amendment recommendations. “The cost is $60 for a couple of samples—less than doorknobs,” he says, “yet it sets up what needs to be done to make that outdoor room look great.”

Low-water-use plants add color and texture to hard-to-water areas such as slopes and median strips. Photo: Denver Water A key tenant of xeriscaping, particularly in arid regions, is to take note of how water flows through a property, manipulating it if necessary to create different planting zones. Landscape architects typically study a property's structure to identify drainage and erosion issues and fine-tune grading. The goal is to create three or four zones, ranging from a small section of water-loving plantings to moderate- and low-water-use zones. Whatever the design scheme, at least half of the plants should be low-water-use, meaning they're able to thrive on once-a-week watering. There is a clear and simple logic to the layout: Plants that require the most water are assigned to low spots where water collects or passes through. Conversely, “you want to install non-thirsty plants in an area where you won't get runoff from the lawn,” says Dave Hanson, senior vice president of landscape maintenance at ValleyCrest Companies, based in Calabasas, Calif. “You don't want them to get water other than from irrigation.” To protect a house's foundation, the lawn, which is irrigated the most frequently, is often located 5 to 10 feet away from the house in a level area. Decks, terraces, stones, and water-sparing plants are appropriate choices for the transition areas near the house.

In a xeriscape, woody shrubs and perennials push back the suburban yard. The lawn shrinks to a functional size—just big enough, say, for a game of croquet or exercising the dog—and is irrigated separately from other plantings. Ball says a 3 percent to 5 percent slope is optimal for a useful lawn. Anything less than 2 percent is considered too flat for good drainage. “If there's not enough slope to get water off a property, it's a problem, but if the slope is too steep, the water leaves the site,” he says. Often, homeowners are sinking every dollar they've got into building the house, and several years can pass before they get around to the landscape. So Ball suggests that builders cast a critical eye on drainage issues before they leave the house in the homeowner's hands. “If a slope is greater than 3:1, builders should advise their clients to figure the cost of building terracing walls into construction costs” so that water can be directed to where it's needed most, Ball says. “Too often they find out later that they have to build a structure and haven't budgeted for it, and the effects of that erosion last years and years.”

Photo: Denver Water Water Wise. After matching plantings to microclimates, xeriscape experts turn to technology to dispense just the right amounts of water, and at precisely the right time. Charlie Schaul, president of AridScape Concepts, headquartered in Phoenix, works with builders six to eight weeks prior to the house's completion to install irrigation systems that respond to the microclimates within a master planting plan. Schaul says that irrigation represents roughly 35 percent of the landscape budget, or $1.50 per square foot, depending on the plant count. “Even in xeriscape, we do one emitter per plant,” he says. Exacting amounts of water are doled out in frequent, short cycles through a low-pressure drip system that operates at 30 pounds of pressure per square inch. “The key component is the emitter selection,” Schaul says. Placed out of sight below grade, their flow rates vary from ½ gallon per hour up to 12-plus gallons per hour. “We have clients regularly call and say, ‘We can't see the irrigation. We don't know if water is flowing,'” Schaul says. “I tell them that if the plant is thriving, it's working.”

Non-thirsty perennials and shrubs are a wise planting choice next to hard surfaces, which create a hot, dry microclimate. Avoid highly irrigated turf areas beside walkways to prevent run-off. Photo: Denver Water Although irrigation technology has come a long way since the 1980s, even the most sophisticated timers and moisture sensors are starting to seem crude. What's state of the art now are evaporation transportation controllers, which are satellites that receive information from weather stations and pass it on to individual irrigation systems. “The station records solar radiation, wind, temperature, and humidity, and runs it all through a formula that calculates evapotranspiration,” explains Jim Knopf, a Boulder, Colo., landscape architect and the author of Water-wise Landscaping with Trees, Shrubs, and Vines. Based on those numbers, the irrigation system adjusts water flow. He says at least two large companies—WeatherTRAK and Weathermatic—offer the technology for residential landscapes.

David Winger, a water conservation specialist at the Denver Water Department, points out that every new home built means another water-demanding landscape. Although water's scarcity is most pronounced in the West, “in the East, rains are seasonal, and reservoir capacity is becoming inadequate for the number of people,” he says. As the human population grows, xeriscape principles are making as much sense in Atlanta as they do in Albuquerque.—Cheryl Weber is a freelance writer in Severna Park, Md.