Xeriscaping: The X-Factor in Gardening

An article dealing with water conservation in a growing season in which rainfall has been timely and plentiful might seem a bit unnecessary. Yet, on a national level, water remains as one of our most precious natural resources and is becoming more and more in demand as the population density increases in areas where natural precipitation is limited. Population growth alone is not putting a burden on our water supply. In the twentieth century the United States witnessed a six-fold increase in its water usage while experiencing only a two-fold increase in its population. Our current elevated standard of living which to many includes the luxurious consumption of water must shoulder much of the blame for any water crises which might exist.

Agriculture is the chief consumer of water in our county. While many would not argue against the use of supplemental irrigation to produce food, there are those who object to the use of our water supply to irrigate our lawns and gardens. Without entering into a discussion concerning the importance of aesthetics to quality of life, most of us would agree that water is a very valuable natural resource that should be used wisely. Xeriscaping is a method of gardening designed to do just that.

The term "xeroscaping" was coined in 1981 by the Denver Colorado Water Department. It comes from the Greek xeros which means dry and scape which refers to landscape, or our created (man-made) environment. In actual practice, xeriscaping refers to the creation of a landscape that has been carefully planned to tolerate dry conditions. Xeriscapes, therefore, need little additional water applied to them and are very environmentally friendly when it comes to water usage.

The most basic component of any landscape is the soil. Healthy soil grows healthy plants. While good soil cannot replace the need for water in a plant, it certainly can help to accommodate plants by promoting good root growth as well as doing a better job of infiltrating and storing water applied to it, be it natural or supplemental. Depth and physical structure are two major concerns of landscape soil. A well-drained soil between 8 and 12" in depth is considered ideal for most landscape plants. Well-drained generally is defined as the ability of soil to absorb ½” or more of water per hour and is characteristic of a garden loam high in organic matter. Unsatisfactory soils can be improved through the addition of copious amounts of well-decomposed organic matter (e.g. sphagnum peat moss or compost) before planting; the deeper the incorporation of this organic matter into the soil, the better will be the results. Organic matter helps to make the soil more porous to water while at the same time enhancing its water storage ability. In areas where annuals are planted and the soil is worked on a yearly basis, the addition of organic matter should be a regular cultural practice. The next step in creating a xeriscape is proper plant selection. Xeriscaping emphasizes the use of water-efficient and drought-tolerant plants in the landscape. This often includes the use of native plants which are well adapted to the region and have proven themselves to be tolerant of the area’s rainfall amount and seasonal temperatures. Grounds for Gardening guide G6660 describes many of these species in detail. Non-natives do not necessarily have to be excluded from the xeriscape and can be used to add interest in the form of texture and/or color. When selecting non-natives, look for species that are native to areas with limited amounts of natural precipitation and are well-suited for dry conditions. Table 1 lists a number of species (mainly non-native) that are tolerant of dry conditions, to various degrees. Additional species can be found. As a general rule, plants with small, highly pubescent or light-colored leaves are more drought tolerant than their alternatives. Higher water use plants do not have to be eliminated from the landscape entirely but should be grouped together in locations that suit their needs and where they can be grown with minimal amounts of supplemental water.

One of the most important components of a beautiful and lasting landscape is proper maintenance, and even drought-tolerant plants require maintenance. Proper maintenance will not only make your garden more attractive, it will help to conserve water as well. Weed control is of utmost importance in the xeriscape since most weeds are glutenous users of water and often are able to out-compete with landscape plants for this precious commodity. Mulching is one of the best and easiest ways to control weeds while at the same time conserving water. In addition to smothering weeds, mulches create a vapor barrier over the soil, thus retaining moisture and helping to keep the soil cool. There are many landscape mulches available for use; those that are organic in nature (e.g. shredded bark or pine straw) have the advantage of adding organic matter to the soil as they decompose. Adequate fertility also can be helpful in water conservation by promoting plants to develop deep, well-branched root systems that have access to greater amounts of moisture in the soil profile. One must be careful not to over apply fertilizer, however, since excessive, lush growth will increase a plant’s water and maintenance requirements.

Finally, for those with the ability to apply supplemental water (if needed) proper irrigation practices can go a long way in making the best use of the water applied. One should irrigate landscapes early in the morning when losses by evaporation will be minimal. Additionally, it is important not to apply more water at any one irrigation than the soil profile to the depth of a plant’s root system will hold. For most garden loams, this is about 1 - 1 ½ " of water per application. Frequent, shallow watering discourages the development of deep root systems able to make better use of natural precipitation.

A lack of water does not necessarily dictate a dull and lifeless landscape. Through appropriate planning, soil preparation, plant selection and landscape maintenance, a balance can be achieved that fits both the aesthetic needs of the owner and the resource availability of the region.

Table 1. Plants tolerant of dry conditions
Annuals:	Verbena	Lenton Rose
Ageratum	Wax begonia	Liatris
Cleome	Zinia	Peony
Cockscomb		Perennial salvia
Coleus	Perennials:	Purple coneflower
Cuphea	Ajuga	Rudbeckia
Dusty miller	Aster	Russian sage
Flowering tobacco	Astilbe	Sedum
Geranium	Baby's breath	Statice
Gomphrena	Beebalm	Stokes aster
Marigold	Blanket flower	Tritoma
Melampodium	Baptisia	Veronica
Mexican Sunflower	Butterfly weed
Ornamental kale	California poppy	Ornamental grasses:
Ornatmental pepper	Creeping phlox	Feather reed grass
Ornamental sweet potato	Coral bells	Fountain grass
Petunia	Columbine	Miscanthus (all species)
Portulaca	Coreopsis	Ravenna grass
Salvia	Foxglove	Ribbon grass
Sanvitalia	Golden rod	Sea oats
Scaevola	Hardy chrysanthemum
Sweet alyssum	Hosta
Snapdragon	Iris

David Trinklein, Associate Professor, Horticulturist, UMC (573) 882-9631