Xeriscaping is a style of landscaping that saves water by using only drought-tolerant plants that can survive without supplemental irrigation. It almost always means changing the plant mix to less grass and more ground cover and shrubs but keeping trees for climate amelioration.
Water is one of our most valuable resources and when it is in short supply, life becomes complicated and very expensive. As the human population increases simultaneously with global warming, many areas will suffer from acute water shortages.
In California in the late 1980s a water shortage occurred following several years of drought. It was estimated that landscaping used 30 to 50 percent of all residential water. To cope with the shortage, many municipal ordinances for water conservation were passed and programs with monetary incentives were introduced. The city of Mesa offered a $231 rebate if 50 percent of the total landscaped area was covered with inorganic mulch such as decomposed granite. The North Marin Water District offered $50 for each square foot of lawn replaced with drought-resistant plants.
Many areas of the Southwest, particularly desert areas, have had longstanding water problems. Creativity always follows need and so xeriscaping was born. The term xeriscaping was invented in 1981 in Colorado. As water prices increased and more frequent shortages occurred nationwide, it became a new landscape style.
Essentially it follows standard criteria for sound landscaping design, except that it uses plants that have low water requirements and can stand the rigors of their local climate. It also takes into consideration such things as natural soil conditions, mulching, waste-water use and more efficient irrigation.
Using plants that can tolerate the climate and microenvironment into which they are placed is just common sense. When the early settlers went across America in their covered wagons, however, they tried to bring with them the familiar landscape they had left behind.
The lush green trees and field of the East were in their minds and so they planted trees and lawns, much as the princess of ancient Babylonia who craved the green northern lands of her youth and so inspired the famed hanging gardens of Babylon. But in California and the American Southwest, as in the Mesopotamian desert of old, keeping things lush and green required constant irrigation.
As the population of the American Southwest kept increasing and as ground water was pumped at ever-increasing rates, it became clear that keeping the imported “artificial”landscapes was becoming more and more of a burden on the water resources of the region.
Xeriscaping in every part of the country aims to replace these eastern landscapes and their eastern plants with native ones that are more at home in the local climates. Replacing high-water-use plants with low-use ones adapted to their particular location can save 20 to 43 percent of water use. Furthermore, a landscape designed from scratch for low water use can cut water dependency by 50 to 60 percent.
In desert places like Arizona, it means using cacti, native desert flora and other drought resistant plants instead of the usual thirsty grass and palm trees. Ground surfaces are covered with decorative stones or sand. The effect is different but quite beautiful, like the desert itself. It has been incorporated into the central highway strips in many desert cities which were depleting their water supplies to keep the palms and grass highway dividers lush and green.
In temperate regions and in California, where water is often scarce, xeriscaping is done using native plants, ornamental grasses and drought-tolerant plants. The effect is not so stark as in the desert and can be quite verdant with careful choices of plants.
For planning purposes consult the list on page 3 of drought-resistant plants and the climate zones in which they will remain hardy.
Which Plants Use More Water?
At the University of California, researchers found that lawns needed the most water to stay green and attractive, which explains why they are so successful in cool, rainy England. Trees, shrubs and ground covers used much less water, although trees used more than shrubs and ground cover for the same area. The ratios were: grass, 8 units of water; trees, 5; shrubs and ground covers, 4.
In hot areas, however, trees use much of their water to contribute to cooling and ameliorating the climate through evapotranspiration from their leaves. Thus, the small amount of extra water they use is returned in human comfort and air-conditioning savings.
An interesting fact is that a multilayer canopy of trees over a shaded lawn actually conserves water. It seems that in the shade, the water requirements of a lawn are reduced by 95 percent over its needs in full sun.
Using Drought-Tolerant Plants
Xeriscaping merely codified and gave a name to a practice that good landscape design has always used. In all landscape design, the choice of plant material should always be scientific. Among the first considerations must be to match the annual rainfall of any area with the water requirements of the plants to be used; otherwise, irrigation must be supplied. It is just common sense.
Unfortunately many developers, in their quest for exotic appeal, have planted things that need to be coddled and fussed over, at great cost. At one of the fancy hotels in the arid part of California, the geraniums alone cost $40,000 a year. All the plants have to be constantly irrigated and fed with soluble fertilizer to make them green and flowering. The gardens are a veritable wonderland, a make-believe place somewhere between a perennial border of an English garden and an Arab harem garden. Disneyland is the same fantasy land with its constant irrigation, fertilizing and oft-changing floral displays. Xeriscaping is a response to this type of resource-wasteful excess.
California Polytechnic University, working with the Water Resources Board of Orange County, prepared a list of all the plants growing in Orange County, then looked up the annual rainfall in their native habitat. The aim was to find which could survive with less irrigation. It is interesting how many varied plants are growing there.
For example, Japanese viburnum comes from an area where the rainfall is 82 inches per year. Podocarpus gets 124 inches of rain in its native Japanese habitat. A different variety of podocarpus is a graceful forest tree that grows happily in the mist-laden rain forest on the slopes of Mt. Kenya. The annual rainfall for deodar cedar is only about 10 inches in its native India, where the fragrant wood is used for incense. Yet all of these varied trees have been planted in Orange County, California despite their different water needs. It is obvious there is much room for improving the use of water by more thoughtful choices of plant material.
Lowering Water Consumption
Desert cities in the Southwest have made enormous strides in their efforts to reduce water consumption in their landscapes. As Tucson’s population and farming grew, water was pumped from the underground aquifer at a rate that threatened the future of the whole system. To conserve water, the city replanted its heavily irrigated grass-and-palm-tree highway dividers with cacti, wild grasses, and native trees. Instead of looking like Florida, the highways in Arizona now look like part of the surrounding desert.
Santa Fe, New Mexico, has planted native desert species extensively, making this beautiful city seem like a gentle continuation of the surrounding natural desert. The whole effect of well-done xeriscaping can be quite beautiful and aesthetically satisfying.
The use of native species is now quite in vogue everywhere. It is another part of the environmental sensitivity that is becoming our cultural continuum. The use of native plants is nowhere more sensible than in low-water-use landscapes. Many of the wild plants and flowers are quite beautiful in their own way, although perhaps not so showy as horticultural varieties developed for their large blossoms. Yet the effect with native plants can be very romantic, not in the style of an English Victorian garden, but more like our western open spaces, rustic and unmanicured.
Desert-style landscapes are encouraged by the trend makers, especially since many movie and TV personalities have homes in states that still have wide-open natural vistas, states such as Montana and New Mexico. Homeowners are encourage, by government agencies, through education and by the more compelling reason of rising water prices, to adopt the principles of xeriscaping as part of conservation in general.
Areas other than the desert or water-poor states benefit from xeriscaping, too. Water is expensive everywhere, particularly in urban or heavily populated places. Metropolitan areas such as New York have problems delivering enough clean water. In the Hudson River Valley, the same water is used, cleaned and recycled many times as it passes from community to community until it reaches the ocean.
In areas where water is scarce and expensive, xeriscaping makes sense despite adequate rainfall. On Long Island, New York, the underground water aquifer is rapidly being depleted. In a demonstration xeriscape garden there, some of the plants being tested are artemesia, broom, potentilla, juniper, Russian sage, sedums, hypericum, daisies and coreopsis, as well as ornamental grasses. Although rainfall is adequate on Long Island and ocean mists humidify the air, there is still a need to conserve water by growing plants that don’t require supplemental irrigation.
Even areas such as the mid-Atlantic states, which have generous rainfall, can benefit from using drought-tolerant plants for those times when rainfall is below average.