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By Dr. Gary L Wade
Extension Horticulturist
University of Georgia

What if you relied on municipal water supplies for landscape installation and you were told by local elected officials that all outdoor watering of landscapes was prohibited until further notice? Furthermore, what if you were told that new landscape installations could be watered only on the day they were installed? What if fines of up to $1,000 per violation were imposed, with multiple citations resulting in incarceration? These situations are not fairy tales – they happened in many urban counties in the United States during the summer of 2001 as a result of three consecutive years of drought that has plagued most of the country.

Unfortunately, periodic drought is only part of the problem. The real problem stems from a growing urban population competing for available water supplies. Today, approximately 75% of the population in the U.S. lives in and around metropolitan areas. As urban areas continue to grow and water resources become more limited, the challenge facing the landscape industry is how to maintain environmental quality while using significantly less water. How are we going to drought-proof our landscapes without sacrificing their quality? No doubt it’s going to require us to change our approach to landscape design and management, paying closer attention to site/plant interactions, the water requirements of plants, and ways to conserve water in the soil.

The Practical Aspects of Xeriscape-type Landscapes

People tend to shy away from unfamiliar terms, and Xeriscape is one of them. Most folks, particularly in the Southeast and Southwest, have heard the term, but many still don’t know what it’s all about. I often hear people refer to it as Xeriscaping, as if it’s strictly a design term, but it’s much more than design. Some landscape firms use the term “water-wise landscapes” which has a more practical meaning to clients.

Xeriscapes are quality landscapes that use significantly less water than conventional landscapes. The concept is based on a set of seven common sense principles for water conservation. These include Proper Planning and Design, Soil Analysis, Appropriate Plant Selection, Using Practical Turf Areas, Installing Efficient Irrigation, Applying Mulch to Conserve Moisture, and Appropriate Maintenance to Assure Continued Water Conservation. The more of these principles one implements, the more water-wise a landscape becomes.

It is not the intent of this article to take an in-depth look at each of the Xeriscape principles, since there are several books and many publications that do that. Instead, I’d like to focus on some of the key elements of Xeriscape that can be used to condition and prepare the landscape for periods of limited rainfall.

Divide the Landscape into Water-use Zones and Begin Conditioning Areas for Lower Water Use

In Xeriscape design, the landscape is divided into three water-use zones: high, moderate and low. In high water-use zones, plants are watered as needed to maintain optimum growth and aesthetic appeal. Plants in the moderate water-use zones are provided no supplemental irrigation. Whether designing a new landscape or maintaining a well-established landscape, it’s critical that you walk the property and establish or re-establish well defined water-used zones. In established landscapes, you’ll likely discover areas being unnecessarily irrigated.

Ideally, less than 10% of the total landscaped area should be high water use, less than 30% should be moderate water use, and at least 60% or more should be low water use. It’s a well-established fact that plants irrigated regularly for optimum growth tend to develop shallow root systems. It’s not uncommon for plants irrigated by a timeclock to be watered two to three times per week, whether they need it or not.

Weaning plants off water is like taking a drug addict off drugs; it takes time and patience. Start by cutting the current frequency in half. After 3 to 4 weeks on this schedule, reduce the irrigation frequency again by irrigating plants only when they show signs of moisture stress. Meanwhile, placing additional mulch over plant roots will help reduce irrigation frequency. It’s likely that you’ll identify several high-use zones that can be shifted to low water use with minimal impact on plant quality.

Retrofit Established Landscapes to Reduce Irrigation Requirements

As you analyze the water-use patterns of landscape, you may discover that it is impossible to significantly reduce irrigation frequency in a particular area without also sacrificing quality. Therefore, a retrofit of redesign of an area may be necessary to reduce its long-term irrigation requirements. For instance, a lush, green turf area near the entrance to a property may decline or look unattractive when irrigated less frequently, so changing it to a natural mulch area with groupings of ornamental grasses, drought-tolerant perennials or spreading ground cover plants may be a cost-effective alternative. Replacing a large bed of annuals that require frequent irrigation with drought-tolerant herbaceous perennials, such as Purple Coneflower, Black-eyed Susan or Lantana, is another example of how an area can be shifted toward lesser water use. Granted, the plants used in the retrofit will require regular irrigation during establishment, the long-term benefit will be a reduction in irrigation without a loss of aesthetic quality.

During the dormant winter months, it may be necessary to move certain established plants to more suitable locations in the landscape where they are less prone to moisture stress. Azaleas, for instance, are best grown on an eastern exposure where they are shielded by a building or other plants from the hot afternoon sun. When planted on a hot, western exposure, their demand for water increases. Therefore, the best long-term solutions are to relocate the plants to an eastern exposure or to provide shade by building a structure or planting a taller plant adjacent to them to cast shade upon them in the afternoon.

Match Plants in the Local Environmental Conditions

Drought-tolerant plants alone are not the solution to a drought-proof landscape. They also must be suited to the local environmental conditions. Junipers, for instance, are extremely drought tolerant, but when planted on a site that periodically floods or stays too wet, they become prone to insect and disease problems and are likely to decline or die. Likewise, native plants are not necessarily drought tolerant unless they are known to be drought tolerant in their native environment. Local site conditions must also approximate the native environment of the plants. Otherwise, they can be high-maintenance nightmares.

Mulch and Amend to Conserve Water in the Soil

Today, thanks to landfill legislation, a growing number of municipalities and private firms are grinding woody brush and selling bulk quantities of mulch and compost to local citizens. Many college campuses have their own grinders and wind-row machines for recycling their organic trimmings. These products absorb water and reduce evaporative water loss from the soil and are invaluable during periods of limited rainfall. However, to avoid possible plant growth difficulties, always use decomposed organic compost as a soil amendment and non-decomposed organic material strictly as a mulch on the soil surface.

Grasscycling, the process of letting grass clippings fall back to the turfgrass, has been shown to prevent evaporative water loss from the soil by acting like a mulch at the base of the grass blades. The important thing to remember, is to mow often enough so that no more than 1/3 of the leaf blade is removed at each mowing. That way the clippings remain small and can easily settle between the grass blades.

One concept for homeowners is to place moistened newspaper, two to three sheets thick, over the planting bed when planting annuals and perennials. Once in place, make holes in the newspaper and plant right through it. Then cover the newspaper with an organic mulch to conceal it.

Reduce Top Growth and Water Demand on the Roots

In each area of the country, drought is more likely to occur during certain months of the year. So as the drought-prone months approach, start reducing vegetative demand for water by fertilizing less frequently and at lower rates. On established trees and shrubs in the Southeast, one application of fertilizer in spring is usually sufficient for the entire growing season. When an extended drought occurs and irrigation restrictions are in place, no doubt some plants are going to wilt, particularly herbaceous plants. When this occurs, the only option may be to cut back plants to reduce their foliar demand for water. If you don’t do this, they are more likely to reach the so called “permanent wilting point” and die completely. The amount of pruning done depends on the type of plant. Some annuals can be cut back close to ground level and will re-spout when normal rains return.

Although drought restrictions on outdoor water use bring sever financial hardship to many areas of the landscape industry, they also signal a time for change and transition as well as new opportunities for environmental stewardship and resource conservation. Success will come to those willing to change with the changing times.

Accompanying Story: Economic Benefits of Water-saving Landscapes

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