University of Missouri Extension

G6912, Reviewed September 1998

Water-Efficient Gardening and Landscaping

Denny Schrock
Department of Horticulture

It has been estimated that many gardeners use about twice as much water in their landscapes as is needed. In most gardens, the amount of water used can be reduced without creating serious plant problems. In Missouri's climate, water-efficient gardening is an important approach to wise water use.

Water-efficient landscaping does not mean using only desert plants. In Missouri it means making an existing landscape or garden more water efficient or developing a new site with low water needs.

Observe native plants along roadsides. Gather ideas for plants to use in low water use zones by observing native plants along roadsides or other undisturbed areas.
 

Purple coneflower Another native perennial flower that will prosper in low water use zones is purple coneflower (Echinacea purpurea).
 

Planning the garden and landscape

Homeowners have two options in developing a water-efficient garden and landscape:

On large sites, both approaches may be possible as new sections are developed while older areas are remodeled.

The three zones

Water-efficient sites are organized around three major water-use areas. While three zones fit most situations, in some landscapes only one or two might be needed. The three zones are based on water needs throughout the year.

Ornamental grasses Many ornamental grasses make excellent choices as plants that will prosper in low water use zones.
 

Complex landscape Complex landscapes with unusual plants often require larger areas to be designated as high water use zones.
 

Established landscapes

Creating water use zones may be more difficult in existing landscapes where many different plants are already established. However, it may be possible to create a low water use zone in an existing landscape. As water availability is reduced, some plants may not survive and will need to be replaced by more durable types. In certain situations, a few especially valuable plants may be watered individually during stress periods while the rest of the area is not given any extra irrigation at any time.

Various means such as mulching, shade, efficient irrigation methods and hardscape surfaces can be used to make the established landscape, as well as a new landscape, more water efficient.

Oak trees are one of the best sources of shadeOak trees are one of the best sources of shade whether for low, medium or high water use zones.
 

Plant selection

In planning new sites or adding new plants to existing sites, whenever possible you should choose plants for most of your landscape that can survive short periods of heat and drought.

Selecting plants for the high and medium water use zones is easy. Practically any plant that will survive Missouri's climate can be used in the high-use zone. In the medium-use area, most plants that form large, deep root systems can survive with watering only during stress periods.

Plants for the low water use area need more careful consideration. A good way to determine which plants can endure in the garden or landscape without extra water is to observe native plants. While we should not dig plants indiscriminately from native areas, the types of plants in these areas may well be the best indicators of what to use in a low maintenance landscape. Here are a few suggestions:

Shade trees

Small and flowering trees

Shrubs

Not all shrubby plants suitable for the low water use area need to be natives. Among plants to consider are

Butterfly weed Butterfly weed (Asciepias tuberosa) is a native perennial flower that is excellent for low water use zones.
 

Perennial flowers

Some native flowers make an interesting addition to the low water use perennial flower border.

Do not consider these plants as the only ones that are suitable. You are sure to find others, both native and introduced, that have excellent low-maintenance potential. The plants listed are suggested only as a beginning in the selection process.

Soil improvement

The better and deeper the soil preparation and improvement, the greater will be the plant's ability to survive. Plants in soils that are shallow or rocky or have a hardpan where roots cannot penetrate will have poorer low-moisture endurance than those in deep, loose soils where roots can penetrate deeply and easily.

Since many landscapes have poor and shallow soils, soil improvement becomes important when establishing a low water requirement area. Dig or till the soil as deeply as possible before planting. If a hardpan exists that can be broken up, break it up. If you are planting trees, dig holes as wide as possible but no deeper than the tree's root ball. In clay soils, do not dig holes with smooth sides, since roots will circle the hole and fail to spread fully into the surrounding soil. Potted or balled trees or shrubs produced in very light or organic soils should have a transitional soil zone placed around them to aid establishment and stimulate thorough root expansion.

During the soil improvement process, have a soil test run to establish existing acidity or alkalinity as well as fertility levels. The soils should then be adjusted to be most suitable for the plants being added to the landscape. Adjusting pH, as well as improving fertility, may be necessary for establishing plants to ensure that they will survive under moisture stress.

Turf selection and maintenance

Tips to save water in any lawn situation

Plant establishment

Thorough soil preparation and planting are essential to good plant establishment. However, once the plant is in place, several cultural conditions must be met before the plant will become well established. Most critical is watering during drought periods.

While the goal is to reach a point where no extra watering is needed, new plants with limited root systems need enough water to get established. This is most important in the first season after planting but can remain critical into the second and sometimes even the third year if weather conditions have been poor and root expansion is slow. Most of the frequent watering usually is needed the first season. During very dry, hot weather, one watering each week should be enough to prevent severe damage. Slow, thorough soaking of individual plants or plant beds is preferable to infrequent heavy watering or frequent light watering.

In situations with little water and high temperatures, one of the plant's first responses is for leaves to turn yellow and drop off. This may not happen with all plants, but as conditions become more severe, certain plants may develop leaf scorch. Scorch begins as yellowing and browning along the margins of leaves and may extend inward between the veins. Under severe conditions, some leaves may turn totally brown. If no watering has been done up to the time these symptoms develop, prompt action should be taken unless rains begin. If all leaves on a tree or shrub turn brown, there is little chance for survival.

To determine how well a tree or shrub has become established, closely examine a few new shoots that develop during the first flush of growth in the spring. The growth developed the year after a plant has been transplanted generally will be shorter than the growth of the previous year. As the plant becomes better established, the flush of new growth the next spring should increase in length. As the shoot length becomes more normal, it indicates that the plant has become established and additional watering can be discontinued.

Mulching

Mulching is very beneficial in all water-efficient landscape zones. It is essential where no additional watering is planned. Mulches conserve soil moisture by blocking evaporation. They also keep the soil cooler. Mulches have the added benefit of reducing weeds that will compete for moisture in the soil.

Many materials can be used for mulch. Organic materials generally are considered the best. They should be fairly fine textured and nonmatting. Straw, pine needles, bark nuggets, wood chips and other wood products are excellent materials for various effects in the landscape. Landscape fabrics or black plastic landscape mulch can be used beneath organic mulching materials to provide better weed control and to increase the mulch's ability to reduce water loss.

Rock mulches will control weeds and hold moisture when used in shady areas. In sunny spots, rocks tend to absorb and release heat over a longer period of time, which can increase water loss from nearby plant leaves.

Irrigation

Where irrigation is required, efficient water use is still extremely important. Efficient irrigation systems can save a lot of water. Soaker hoses or trickle or drip irrigation are the most water-efficient systems. Overhead sprinkling generally is less efficient than watering at the soil surface or within the soil. During hot weather, considerable water is lost to evaporation when overhead sprinkling is used.

It is relatively easy to determine how much water has been applied if you are using overhead sprinklers. Wide-mouthed cans or jars can be placed within the sprinkler area. The water collected in them can be measured to keep track of how much has been applied. During dry weather, usually about an inch of rainfall or irrigation water should be applied weekly. During very hot weather, watering may be increased to as much as 2 inches per week.

It is not as easy to determine how much water is being applied when soaker hoses or drip irrigation are used. There always will be more water in the soil closer to the hose or to each emitter than at distances farther away. Check a few spots in the irrigated area by carefully digging out soil with a trowel or spade. Ideally, you want to apply enough water to have the top 6 inches moist but not soggy wet a few hours after the irrigation system has been turned off. If water starts to run off before areas are thoroughly soaked, stop the sprinklers or hoses and do not start water again until the water has penetrated so the soil becomes more absorbent. Efficiency is lost rapidly when water runs off the surface.

Water will be absorbed with less evaporation if you irrigate during the cooler parts of the day. Early morning from 6 to 8 a.m. is ideal because leaves will dry quickly. Evening watering also is fairly efficient, but plants that are susceptible to leaf disease are more likely to be infected if leaves stay wet for too long. The least efficient watering time is during the heat of the day when evaporation is rapid.

Shade

Shade is another element that can be used to save water in the landscape. Where it can be used, shade reduces moisture loss by keeping surfaces cooler. Trees, shrubs and vines can all provide some benefit. Structures such as trellises and arbors also provide beneficial shade, although they do not produce as much cooling as shady plants.

Although trees and other plants lose moisture as they transpire, water released during transpiration cools the atmosphere and the soil. This reduces evaporation from other areas or from plants in their shade.

Some trees are more water efficient in sunny locations than others. A few of the most efficient types in sunny locations are ash, oak, hickory, red maple, sweetgum, pine and walnut. The less efficient trees are classified as understory trees. Understory trees need sun protection from other trees or structures. Trees that are not so efficient and are best as understory trees include beech, dogwood, hemlock, magnolia and redbud.

Shade is particularly useful in places where it keeps heat from building up near hard surfaces that not only become uncomfortably hot, but increase water loss from nearby plants and soil.

While shade is very useful for conserving moisture, not all plants can tolerate shade. Even beneath structures, water management is improved if mulch is used where dense shade might be too heavy for plant growth. Where adequate light exists in the landscape, shade-tolerant groundcovers or other plant materials can provide a similar but more attractive benefit.

Maintenance

Healthy plants are more drought tolerant than weak or damaged plants. In maintaining plants in water-efficient gardens and landscapes, watch out for disease or insect problems that may develop. Be careful to avoid mechanical damage such as bumping tree trunks with lawn mowers or damaging the bark with string trimmers.

Pruning plants can help by reducing the amount of foliage that is losing water. However, trimming should be done carefully. Severe pruning opens up the plant to more sunlight and, consequently, more water loss during midsummer.

Fertilization can be harmful during drought periods when watering cannot be done. If plants need nutrients, delay fertilization until fall or spring when weather conditions are more ideal and there is enough moisture in the soil for plants to easily absorb the nutrients.

In lawns, allow grass to get taller in nonirrigated areas during drought periods. Some grasses will go dormant, but others will benefit from the extra shade and extra photosynthesizing leaf area resulting from longer blades. During drought periods, raise the normal mowing height 25 to 50 percent.

Hard surfaces and heat barriers

There are many areas where hard surfacing cannot be avoided, such as a driveway, walk or patio. Shade is one of the ways to reduce heat buildup in these areas and, consequently, water loss around them. However, in some cases other options are available that have less tendency to build up heat and may also conserve moisture. Light-colored surfaces trap less heat than dark surfaces. Walks built with bark mulch or other organic materials, if practical, will be cooler than concrete or gravel.

Where hard surfaces must be used, a barrier of plants between them and the other surfaces can break the heat flow from one area to another. This may ease the stress on some plants, therefore reducing their water needs. Low fences with durable vines on them may provide such a barrier. Some heat-durable plants, such as junipers, can provide a heat barrier if used as a hedge. Around parking areas, taller plants or fences might be used. Durable vines on the fences along with heat-tolerant shrubs for dense hedges can all be beneficial for saving water and improving the survival of nearby plants.

Heat barriers also can be developed in other ways, depending on the home and the individual landscape. These barriers basically are means for controlling air movement in the landscape. Heat rising from hard-surfaced areas is directed away from plants that are not as heat tolerant as others might be. In addition to keeping hot air away from certain areas of the landscape, the same technique can help direct cool air beneath large trees or near patio areas to make them more comfortable as well as water efficient.

G6912, reviewed September 1998

G6912 Water-Efficient Gardening and Landscaping | University of Missouri Extension

Order publications online at http://extension.missouri.edu/explore/shop/ or call toll-free 800-292-0969.

University of Missouri Extension - print indicia