Wise Water Use in Landscaping
Prepared by:
M.A. Powell, Extension Specialist, Horticultural Science
and
T.M. Disy, Information Specialist
Published by: North Carolina Cooperative Extension
Service
Publication Number: AG-508-1
Last Electronic Revision: March 1996 (JWM)
Water is one of our most valuable natural resources. Most of the time,
however, we take it for granted and use it in abundance until drought sets
in and we areforced to conserve. To protect our water supplyfrom extreme
shortages, we should strive daily to conserve water. This publication
introduces some basic ideas that will help you conserve water and protect
the environment while meeting all of your landscape needs.
One area where water use can be decreased without sacrificing beauty or
function is in landscaping. The term
xeriscaping means landscaping for efficient water use. By using plants that are
drought tolerant and by knowing what
amount of water is right for your landscape and when to water, you can use
much less water.
Beyond conserving water, protecting
water supplies from pollutants that may
come from landscaping is also important.
Best management practices (BMPs) for
landscaping have been developed that
enable you to have a healthy, attractive
landscape while using resources efficiently and protecting our environment.
Xeriscaping and BMPs lead to savings in
time, money, and effort.
Plant only what you can water.
Landscape plants have a variety of water
needs. Plants need the most water immediately after being planted and during
establishment. Before planting, make
sure that you can provide enough water
during this time for the plants that you
have chosen.
Landscape plants are available at
garden centers and nurseries either container grown or balled and burlapped.
These trees and shrubs can be planted
even during a drought if watered at
planting time and at least twice a week
for the remainder of the growing season.
Trees and shrubs, 1- to 3-gallon size, require 3 to 5 gallons of water twice a week
during establishment.
Sodded and seeded lawns have different water needs. Newly laid sod needs
a minimum of 1/3 inch (200 gallons per
1,000 square feet) of water at least three
times a week. Continue supplying this
amount of water for the first two weeks
until sod is well anchored to the soil.
After that time, grass needs about 1 inch
of water each week during the growing
season. For seeded lawns, once germination begins, daily irrigation is needed
until the grass is established. If seeds are
placed in dry soil and not subsequently
irrigated, most will germinate when water is available.
Choose plants based on water
needs.
Many of our southern landscape plants
can live through drought. Once they are
established, plants such as Crape Myrtle,
Elaeagnus, Cedar, Chinese and Japanese
Hollies, Glossy Abelia, and Juniper can
survive weeks without supplemental
irrigation. Table 1 lists plants that are a
good choice for wise-water-use landscapes.
Most healthy, established turfgrasses need about 1
inch of water each week for optimal growth but can
survive at least four weeks without water. Turfgrasses
may turn brown and become semidormant during
drought, but they recover once water is available. The
drought tolerance of turfgrass varies. Once established, warm-season grasses, such as bermuda and
zoysia, require 50 to 75 percent less water than cool-season grasses, such as tall fescue.
With proper selection, establishment, and maintenance, turfgrasses
require much less water than once thought.
The placement of plants is another key component
in efficient water use. Incorporate natural areas into
your landscape design wherever possible. Native
plants, once established, often require little supplemental water and maintenance. Turf, which requires
much more care, is practical in areas of the landscape
where it serves a function, such as in recreational areas, on slopes to control erosion, or where it lends
aesthetic value. When you begin planning your landscape, divide the area into low-, moderate-,
and high-water-use zones and locate plants accordingly.
Learn the symptoms of drought stress.
Different plants show different drought-related symptoms. The leaves of some plants may exhibit marginal
leaf burn, whereas others simply wilt. Some daily wilting is normal during hot summer days, but prolonged
drought conditions can cause continuous wilting. For
trees and shrubs, wilting is one of the first signs of
drought stress.
Certain plants in the landscape wilt readily and
can be used as early indicators of drought stress.
Plants to watch for signals that it is time to water include azaleas, dogwoods, hydrangeas, most annuals,
herbaceous perennials, and turfgrass. The first symptoms
of moisture stress in turfgrass are a dull grey-green color and leaf blade folding or rolling. It is most
effective and efficient to wait for these symptoms of
stress before irrigating.
An extended drought, however, may result in
irreversible wilting from which the plant does not recover.
Leaves may wither and remain on the plant or drop
completely. Extended drought may also cause death of
twigs or of the entire plant. Learning to watch for the
symptoms of drought stress will help prevent your
landscape plants from reaching this point.
Establish priority needs for water.
When water is scarce, consider which plants should be
watered first, second, and third, taking into account
plant value, replacement costs, and time to grow a
comparable plant. Plants that can be grown readily
from seed, such as turfgrasses, annuals, and herbaceous perennials, are relatively easy to re-establish if
lost during drought.
On the other hand, large trees with historical
value or social significance may be impossible to replace. Plants providing major emphasis or form to the
landscape design also deserve special consideration.
Newly planted trees, shrubs, and turf are especially
prone to drought damage.
Manage the soil for efficient water use.
Preparing the soil thoroughly helps assure good root
growth. Research has shown that digging a wide
planting hole and tilling the soil thoroughly improves
the structure of the soil and results in rapid plant establishment and better root growth. Whether or not
soil amendments should be added depends on the
structure and texture of the soil, the water-holding
capacity of the soil, and the type of plants to be
grown. Heavy clay soils have a high water-holding
capacity and will benefit from adding some type of
coarse aggregate, like pine bark, which will improve
the ability of water to move through the soil. Sandy
soils, on the other hand, may not hold enough water
and nutrients for plant use. Adding fine-textured organic matter to these soils may be helpful. Your goal
should be to provide the roots of plants with a moist,
well-drained, and well-aerated growing environment.
Mulching can also decrease your landscape's water needs. Three to five inches of mulch, such as pine
straw, pine bark, aged wood chips, or compost, help
conserve soil moisture. Mulch also insulates the root
system of plants from heat and helps control weeds
which compete with the plant for water. Fine-textured
mulches, such as pine straw or mininugget pine bark,
retain more moisture than coarse mulches. On sloping
sites, pine straw stays in place better than most other
mulches and helps control erosion. Landscape fabrics
can also be used under mulch to conserve moisture,
discourage weeds, and enhance erosion control.
Manage the landscape to avoid
unnecessary plant stress.
When water is scarce, avoid unnecessary plant stress.
Do not fertilize. Fertilizers are chemical salts and may
damage roots and prevent water absorption. Fertilizers
also stimulate new growth, which increases demand for water. Pruning also stimulates new growth
and should be avoided during water shortages.
Table 1. Suggested Plants for Xeriscaping. For a more complete listing of plants refer to Drought Tolerant Plants.
That publication is included in this series and is available from your County Cooperative Extension Center.
Trees
Shrubs
Ground Covers/Vines
Annuols & Perennials
Drought-stressed plants are susceptible to damage from insects and diseases, but pesticides may
damage the plants. Watch for signs of plant damage
from insects and disease pests and control them before they can weaken plants and increase the plants'
need for water.
The same practices apply for turf. Another consideration, however, is mowing. Frequent mowing
results in a healthier root system and more drought-resistant turf. Raise the mowing height, and mow
often enough that no more than one-third of the leaf
tissue is removed. Keep the mower blade sharp; a dull
blade causes more plant water loss and undue stress.
Be conservative with irrigation.
Pattern irrigation systems to meet the water needs of
particular plant zones. The best time to water
landscape plants and turf is during the night, from dusk to
dawn. Less evaporation occurs during this time, and
the plants can make more efficient use of the water.
Applying water as slowly as possible through
trickle irrigation or soaker hose improves absorption
into the soil. Trickle or drip irrigation of trees and
shrubs reduces water use by as much as 50 percent
compared to conventional sprinkler irrigation.
Trickle, drip, and subsurface irrigation, however, are
not effective on turfgrass
Water applied too rapidly may run off and be
wasted, particularly on slopes. A timer installed on
outdoor faucets to control the period of irrigation will
prevent unnecessary water use. One inch of water (5
gallons per square yard of surface area or 620 gallons
per 1,000 square feet) applied once a week on established
plants and turf is recommended. For trees, at
least 50 percent of the root area should be watered.
The root zone of large trees and shrubs can extend
well beyond the drip zone. A thorough soaking of the
soil once a week is much better for plants than light,
frequent irrigation that encourages shallow rooting.
Distributed in furtherance of the Acts of Congress of May 8 and June 30,
1914. Employment and program opportunities are offered to all people
regardless of race, color, national origin, sex, age, or disability. North
Carolina State University, North Carolina A&T State University, U.S.
Department of Agriculture, and local governments cooperating.
AG-508-1
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