The word xeriscape comes from the Greek word ?EUR??,,????'??Xeros?EUR??,,????'??, meaning dry (xenscape). Therefore, a xeriscape is, by definition, a dry landscape. However, because plants need water to survive, true xeriscape is a landscape based on the utilization of drought-tolerant and drought adaptive plants with the minimum irrigation necessary to sustain the plants.

Two components are essential to dry landscaping: water and plant material. How much water and what type of plants greatly affects the appearance and efficiency of the garden, whether a backyard area or the commercial landscaping at Sea World. Plants can be overwatered, and 8-10% of plant problems are attributed to too much water. In addition, overspraying sidewalks and streets accounts for a 90% increase in deterioration, not to mention the increased probability of liability due to accidents. Proper watering, the correct amount in the correct place, saves time and money by reducing water bills, plant replacement costs and hardscape repairs.

Water zones are the areas of a garden defined by sun exposure, shade and location. When planning an irrigation system, the separate sections of the yard must be considered and irrigated separately, if practical. An irrigation design should provide separate irrigation for turf, shrubs and groundcover, north, south, east and west sun exposures. Keep in mind that turf is the greatest water user and should be incorporated into a xeriscape design sparingly and preferably be planted with drought tolerant grasses such as Bermuda and fescue. The southwest area of a yard requires more water, while the northeast and shade areas require less. Groundcover, shrubs and mature trees require less frequent water application. Most grass or turf needs watering two to three times per week during warm weather, depending on soil type. More frequent irrigation may result in a yellow-green appearance, weed invasion, disease, soil compaction, deep root loss and wasted water. Any new planting, of course, needs frequent watering until established.

How these areas are watered depends on plant needs and the concern with water conservation. There are three main types of irrigation: 1) flood ?EUR??,,????'??? which is fine for growing rice and some agricultural crops but not suitable for landscape because of its cost and waste; 2) overhead spray ?EUR??,,????'??? which covers large areas effectively, providing walkways and streets aren?EUR??,,????'???t oversprayed and the time of day, wind and amount of water used is monitored. Evapotranspiration, the evaporation and transpiration (evaporation direct from the plant wall rather than from the air), greatly increases water use. Therefore, it is recommended that nighttime irrigation is used; 3) drip irrigation ?EUR??,,????'??? is ideal for shrubs, trees and groundcover. Emitters (the controlling outlets along a length of irrigation pipe that allow water to flow out in droplets) provide deep irrigation to root zones with little or no evaporation or water runoff.

An Understanding Of Evapotranspiration Is Primary To Understanding The Plant/Irrigation Relationship

The perfect irrigation system is based on quantitative data regarding soil type, weather, water scheduling, application of water, the installation and maintenance of irrigation equipment and efficient use of that equipment.

In certain cases, gradual weaning of some plants from their accustomed water ration not only benefits the owner by lowering water costs, but can have a beneficial effect on plant material. Controlled water deprivation to flowering species frequently results in increased blooming and can increase the plant?EUR??,,????'???s health and disease resistance, by eliminating the chances of shallow root rot caused by fungi. As Irrigation Consultant Daniel Scaliter sums up, ?EUR??,,????'??Remember, plants require a certain amount of water, no more, no less. You can overwater with any method of irrigation and plants will tolerate more water than needed up to a certain point. The key is know and understand the plant material?EUR??,,????'???s minimum requirements and applying water accordingly.?EUR??,,????'??

An understanding of evapotranspiration is of primary importance to understanding the relationship between irrigation and plants.

Evapotranspiration (ET) is the loss of water from the leaves of a plant, coupled with the evaporation from surrounding soil. The rate at which this vaporization takes place is dependent upon sunlight, temperature, relative humidity, wind speed and density and forms of plant materials. Drought tolerant plants generally use significantly less water. But there are variations of drought tolerance. Eucalyptus, normally considered drought tolerant, are water spenders when their ET rates are considered. They have extensive root systems and survive drought only as long as some of those roots are in moist soil. ?EUR??,,????'??Drought-evading?EUR??,,????'?? plants, such as California Buckeye and Bermuda grass, become virtually dormant during dry seasons. Water conserving plants have ways of reducing water loss. Their leaves often are small, gray-colored, leathery, and arranged to reduce the amount of sunlight that strikes them. Many California native plants and plants from similar climates are of this type. Ceanothus, manzanita, and olive are a few examples.

Not all plants can be made drought-evasive, but certain plants can be made drought tolerant. To become drought tolerant, a plant must grow its roots down into the soil where the winter rains?EUR??,,????'??? moisture remains into the dry season. The deeper and more permeable the soil, and the more rain it gets during the rainy season, the greater the probability that a drought tolerant plant will survive. Other factors also govern plant success. The particular plant material must have at least some (if not all) of the above-stated drought evading qualities. Heat, wind and humidity also affect plant survival. Obviously, soils that retain moisture are of more benefit than porous, sandy soils.

Creating drought tolerance requires patience. It doesn?EUR??,,????'???t happen overnight. Generally, irrigate drought-tolerant plants during their first winter and spring if the soil hasn?EUR??,,????'???t been kept moist by frequent rains. Water them two to four times daily during the first dry season. By the second season, most plants won?EUR??,,????'???t need water, although others may. Water requirements can be determined by the amount of wilt in the leaves. If left too long without water, plants suffer shock and may not recover. Monitorthem closely during their first and second season.

When considering the types of plants for a xeriscape garden, it is again worthwhile mentioning that lawn areas are the greatest users of water. True, they are attractive, but the alternatives are numerous and attractive, not to mention water conserving and cost efficient.

Crushed rock, gravel or decomposed granite are relatively inexpensive, widely available, provide good drainage and are elegantly effective in a landscape. Bark and wood chips soak up and retain water, cooling the environment and, at the end of the warm season, can be tilled into the soil to protect against frost damage, and provide a rich mulch. Brick on sand is water absorptive, keeps soil cool and thereby reduces evaporation. Weeds, chief water thieves, can be kept at bay by placing a layer of plastic sheeting down before spreading gravel or brick. Decks are also quite attractive, allow for air circulation and rainwater can seep between the boards, thereby supplementing the soil and cooling the area.

Potted plants, either on the ground or in hanging baskets, can be watered with drip irrigation and again, are not only decorative but frequently act as wind buffers and reduce patio temperatures by allowing air to circulate through and around them.

Water is a limited and precious commodity It is vital to human existence. If we are to survive, we must not only be aware of the finite nature of water but also know that through improper use, we diminish the supply we have. Only by conscientious conservation can it be preserved. We must act now to conserve the water allotted to us. This can be done through xeriscape.

Bret Logan was a Design/Fine Arts major at UCLA and is currently pursuing a degree in Environmental Design. She is co-owner of Scaliter Irrigation Engineering, Inc., an irrigation consulting firm in Southern California, where she has worked since 1986.