Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: https://read.dmtmag.com/i/129601
Landscape Design and Construction inputs of water. In San Diego, for example, more than half of all residential water is used to irrigate lawns and landscapes (Generoso 2002). Using water this way can deplete aquifers, damage habitat in areas from which water is drawn, decrease local agricultural production, and leave our landscapes vulnerable to desiccation when water restrictions go into effect. The negative consequences of landscape irrigation and the countervailing benefits of water conservation motivated Denver Water (the water department in Denver, Colorado) to introduce xeriscaping in 1981. Xeriscaping, from the Greek word xeros, for "dry," emphasizes grouping plants in the landscape according to their water needs (Weinstein 1999). Not surprisingly, many xeriscapes feature xerophytes, plants with low water needs. Denver exists in a semiarid environment, getting on average around 14 inches of precipitation a year, as compared to about 35 to 40 inches a year in most areas east of the Mississippi. Kentucky bluegrass (Poa pratensis) lawns, shade trees, and most common garden plants need additional water to survive. At their former home, Panayoti and Gwen Kelaidis ambitiously replaced their entire front lawn with plants well adapted to Denver's semiaridity. These include sulfur-flower buckwheat (Erio- gonum umbellatum), soapweed (Yucca glauca), and partridge feather (Tanacetum densum ssp. amani). Today, 20 years later, these plants are still thriving with no supplemental irrigation (fig. 1.4). Selecting plants that are adapted to the temperatures and available water of the environment in which they will be placed is a fundamental step in creating an ecological landscape. Create ecosystems Built landscapes also have physical and biological components: crudely, in industry terms, hardscape and softscape. Too often, these components are far from integrated. The hardscape is set in response to programmatic needs, and plants are tucked into the remaining spaces. If the physical environment is not right for the biological components, then it is altered, by providing irrigation, for instance. Consider a typical landscape pond. An estate owner might pay a contractor to clear an area, excavate a hole, line it, fill it full of water from a well, and trim the whole setup neatly with rocks or lawn and perhaps a few aquatic plants on a planting shelf. As water evaporates from the unshaded pond, the well pump kicks in and tops off the pond. Even suburban homeowners want their own ponds and water- falls, full of municipal water and lined with dwarf conifers or Japanese iris (Iris ensata) sitting like rocky puzzle pieces on their lawns. These systems are fully artificial, rely on supplemental water, and often require filtration or even sterilization to remain aesthetically acceptable. Physical and biological elements are divorced from each other and from their surroundings. By contrast, a pond that is conceived of as an ecosystem fuses physical and biological elements into a whole that integrates with, rather than sits apart from, the processes of the surrounding environment. Landscape architects Andropogon Associates created such a pond on a property in Greenwich, Connecticut. Naturally, throughout New England's forests, in the spring small depressions in the landscape fill with water, which infiltrates as groundwater levels drop in the summer. These vernal pools provide important habitat for amphibians such as salamanders and frogs. On this property such a depression existed, set against a granitic outcrop, only it had long been filled with branches, leaves, and other green waste by generations of gardeners. When Colin Franklin, founding principal at Andropogon, discovered the rocky dell and the small spring at its base, he saw an opportunity. Andropogon Associates' design philosophy has long been to build "dy- Figure 1.3 The 2012 USDA Plant Hardiness Zone Map. Note the fairly regular progression of zones from north to south in the center of the continent and the irregular zone boundaries related to mountain ranges and the moderating effects of large bodies of water (including the Great Lakes) in the west and east. — Image provided by the US Department of Agriculture. 16 Landscape and Irrigation May/June 2013 www.landscapeirrigation.com