Landscape Water Conservation: Principles of Xeriscape
Revised by Bernd Leinauer
College of Agricultural, Consumer and Environmental Sciences, New Mexico State University
Author: Extension Turfgrass Specialist, Department of Extension Plant Sciences, New Mexico State University. (Print Friendly PDF)
Photo by Pat Gross
Conserving Water in the Landscape
Water use data from cities in the Southwest show that 50% or more of summer domestic water use goes to outdoor watering. But there are several strategies that can reduce or eliminate potable water use for landscape irrigation as part of a comprehensive effort to conserve potable water in the desert Southwest. They include 1) reducing the area under irrigation, 2) replacing potable water entirely with recycled or low-quality groundwater unfit for human consumption, 3) using efficient irrigation systems and/or irrigation scheduling techniques to maximize irrigation efficiency, 4) using plants that are adapted to the local climate and can survive on less water than traditional plants, and 5) applying a combination of two or more of these measures. Each one of these strategies can significantly reduce or eliminate the need to use potable water for irrigation. In this Extension guide, we describe the concept of xeriscape, which includes but is not limited to the use of locally adapted, drought-tolerant plants that generally require less irrigation water than plants that have been used traditionally.
The traditional urban landscape in New Mexico consists of plants that are native to central or northern Europe, Asia, the East Coast of the United States, and other regions with much higher precipitation. In order to successfully maintain these plants, we must supplement natural precipitation with irrigation. However, using plants with high water demand is not our only landscaping option.
Native landscape plants that require less water can be used instead of non-native ones. They can offer similar aesthetic benefits while providing the same function as their higher-water-use counterparts. A secondary benefit is that plants with low water requirements may also be better adapted to the alkaline soil characteristics of New Mexico and other dry regions. Landscapes using these water-efficient plants are often called xeriscapes.
What is Xeriscape?
The concept of xeriscape was developed in Denver, CO, in response to water shortages. “Xeros” is a Greek word that means “dry.” Xeriscape refers to a landscape that uses little supplemental water. It does not refer to a dry, barren landscape, nor is a xeriscape a “no maintenance” landscape. Like traditional landscapes, a xeriscape may be designed to minimize labor or to require frequent care. By using plants that are well adapted, mulches that suppress weeds and conserve water, and drip irrigation to make the most use of water, these landscapes can have color and fragrance with much fewer gardening chores. However, if you want to spend more time in the garden, a xeriscape can be designed to be as labor-intensive as a highly maintained traditional garden, but to use much less water. There is a xeriscape for every gardener.
Xeriscape does not have to be a single landscape style or garden design. Xeriscape is a concept of water conservation that can be applied to landscapes of any style—traditional, English, Japanese, Southwestern, and others. They may be formal or natural-looking. The principles used to develop xeriscapes are good horticultural practices applied to our unique desert environment.
Xeriscape incorporates seven water-conserving principles:
- Planning and design
- Efficient irrigation systems, properly designed and maintained
- Use of mulch
- Soil preparation
- Appropriate turf
- Water-efficient plant material
- Appropriate maintenance
Landscape Planning and Design
A good landscape or garden begins with a good design. Water conservation in the garden can be maximized if it is considered in the initial planning phase.
Xeriscapes can be divided into zones with different water requirements. An “oasis,” a zone with the highest water use, is usually where people spend more time. The patio area and perhaps the entry area are candidates for the oasis. An oasis receives more water and, as a result, is cooler. This area may also require more maintenance and will usually be the landscape’s most colorful area.
Beyond the oasis is a transition zone of moderate water use. The transition zone contains plants that require less frequent irrigation and usually requires less maintenance. Further away may be a low-water-use zone, which requires no supplemental water or very infrequent irrigation during prolonged dry periods. Designing the landscape with areas of differing water demands is called “hydrozoning.”
“Found water” or “harvested water” that runs off roofs and paving during storms can be used to reduce the need for supplemental irrigation. Roof runoff can be directed to the oasis or other areas, reducing the need for supplemental irrigation in the moderate- and low-water-use zones. Because rainwater harvesting requires grading to channel and detain runoff, it should be planned when the landscape is designed.
Irrigation is necessary in a xeric landscape, at least during the first few years while the plants’ root systems are developing. Following establishment, irrigation may still be necessary depending on the landscape design and plants’ needs. In New Mexico, many landscapes need irrigation for at least a portion of the planted area for the life of the garden. The oasis and the moderate-water-use zones have the greatest need for irrigation, but it is wise to plan irrigation even in the low-water-use zone to allow for new plantings, changes, and years of severe drought.
The irrigation system—whether automatic, manual, or hoses moved as needed—is also an integral part of landscape planning. It is the foundation around which the plantings are designed. The water-use zones—low, moderate, and oasis—should be separate from each other, and each managed independently. With in-ground irrigation systems, each zone should be under a separate valve.
The water should be applied as efficiently as possible. Pop-up sprinkler systems are still most common on turf areas, but these systems waste considerable water due to overspray and wind drift. Subsurface drip systems have recently been introduced to irrigate turf areas, and studies have documented water savings between 30 and 50% when irrigation is applied from the subsurface.
Drip, bubbler, and micro-spray systems or soaker hoses are more appropriate for shrubs, trees, and annual and perennial plantings. Efficient irrigation applies water where it is needed, not where it will be wasted and benefit only non-planted areas and may result in the growth of weeds.
Use of Mulch
Mulch provides a cover over the soil, which reduces evaporation and erosion and moderates soil temperature. It also limits weed growth and therefore reduces competition for water and nutrients. Several landscape mulch materials are available, and they vary in their suitability for different uses.
Impermeable plastic mulch has a function in the landscape, but is very often misused. It may be used in areas where the soil must be kept dry, for example next to a foundation where termiticides have been applied or where you are channeling harvested water from one area to another.
Otherwise, permeable weed barriers, bark, gravel, and other porous mulches are better because they allow water and oxygen to reach plant roots. Dust will eventually collect over the weed barrier fabrics and allow the growth of some weeds, so it is not a perfect solution, but these porous fabrics are useful for weed control when the bark or gravel covering them is less than 3 to 4 inches thick, or where annual weed potential is high.
Organic mulches keep the soil moist and reflect less heat. They work well with plants adapted to cooler microclimates. Bark mulch should not be used on steep slopes or in drainage ways because it washes away in heavy rains.
Some plants native to very well drained soils grow better in gravel mulches. Remember, though, that rock mulch becomes very hot in our climate and can injure or limit the growth of some plants. Ultimately, the mulch should be shaded and cooled by landscape plants. Using gravel mulch alone as a landscape element will increase the temperatures around your house, which may result in increased home cooling bills and require greater weed control efforts.
Soil preparation is an important part of successful xeriscaping and gardening. Taking a soil test before planting can help determine which plants are best adapted to the site and which soil amendments are appropriate for improving the soil for the selected plants. For more information on soil testing, see NMSU Extension Guide A-114, Test Your Garden Soil (http://aces.nmsu.edu/pubs/_a/A114.pdf).
In the oasis and moderate-water-use zones, adding compost increases the soil’s water-holding capacity. In the low-water-use zone, soil preparation may only consist of rototilling to loosen the soil and reduce the soil compaction associated with the previous building construction. Loosening the soil improves root development and allows better infiltration of water and air needed by plants’ roots. This is important in all water-use zones. However, since soil disturbance promotes the germination of weed seeds, limit tilling to areas being planted.
One of the most controversial and misunderstood of the xeriscape principles is the concept of appropriate turf. Turfgrasses have a place in the landscape, even the xeriscape. Turf is easy to maintain, although it requires more frequent care than many other landscape plants. Turf provides a play surface for children and pets. It is an important element in cooling the local environment, reducing erosion, and preventing glare from the sun. Other ground cover plants can perform these functions—except providing a play area.
Consider where and how large a turf area you want, how it will be used, and during which seasons it will be used. Then you can limit turf to useful spaces and determine which grasses will best serve your needs. In northern New Mexico and higher elevations of the state, cool-season grasses are best for areas used extensively as play areas, especially if this use extends into the early spring and late fall. Tall fescue, Kentucky bluegrass, or a fescue-bluegrass mixture is appropriate for these areas. If the use is light or mostly in the warmer months and in southern New Mexico, use a grass that needs less water such as buffalograss or bermudagrass. Other native grasses, such as blue grama, are considered ornamental grasses and cannot be used as turfgrasses. If the area is only for appearance, other ground cover plants may be more appropriate and may be irrigated more efficiently. Choose the best plants for each purpose by carefully defining your needs and purposes before selecting specific plants.
Plants that require less water are becoming more readily available in nurseries. There are many very attractive plants for use in water-wise landscapes. While you may use many of your old favorites in the oasis zone, there is a wide variety of colorful, fragrant, and beautiful plants for the less-irrigated part of the landscape. Many have long blooming seasons and attractive leaves. Some provide autumn interest with colorful foliage and fruit, while others offer winter interest with their fruit, seed stalks, and winter colors ranging from silver to gray to many different green and brown shades.
Xeric plants depend on the formation of extensive root systems to effectively gather water for proper growth. While they may look unimpressive in nursery containers, they rapidly become beautiful plants in the landscape.
Maintenance cannot be forgotten, even in a xeriscape. While many gardeners find the time spent gardening to be very relaxing, people with less time or other interests may prefer a landscape that requires minimal time working in the garden. The design will determine the required maintenance. Any garden will require some maintenance: pruning, removing trash that has blown into the landscape, occasional weeding and pest management, checking that the irrigation system is functioning properly, and adjusting automatic irrigation systems as the seasons change.
Xeriscaping offers a way to have beautiful, livable landscapes without excess water use. It allows areas close to us to be cooler and hospitable, while investing less water on parts of the landscape in which we spend less time. Even lower-water-use areas can be very attractive if the seven xeriscape principles are employed. Using xeriscape makes our landscapes more compatible with our New Mexico environment.
For further reading
H-504: How to Water Your Lawn
Original author: Curtis W. Smith, Extension Horticulture Specialist.
Bernd Leinauer is a professor and Extension Turfgrass Specialist in the Department of Extension Plant Sciences. He received his M.S. and Ph.D. degrees in crop and soil science from Hohenheim University in Stuttgart, Germany. His Extension and research program focuses on developing water management strategies for turf areas to reduce the amount of water used for irrigation.
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New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.
Revised February 2017