Conserving Water in the Garden: Designing and Installing a New Landscape - Oregon State University

1. EC 1530 • May 2001
$1.00
Conserving Water in the Garden
Designing and Installing a New Landscape
A.M. VanDerZanden
Water is quickly becoming one Research has shown that these
of Oregon’s most critical natural water-saving guidelines can reduce
resources. As the state’s population landscape water use by 60 to 80
increases and urban areas expand, percent.
water use and water rights are
becoming increasingly contentious Start with a
issues. landscape plan
Typically, about 30 to 40 percent A water-efficient landscape remaining soil is compacted by
of urban water use is for outdoor begins with a plan. If you are heavy equipment, and construction
activities. In addition to landscape familiar with the principles of rubble is buried. A soil test will tell
maintenance, outdoor water use landscape design, you might want you whether nutrients are lacking.
includes washing cars, driveways, to draw your own plan. Another Dollar for dollar, soil improvement
and sidewalks, and filling swim- option is to hire a professional to is the best investment you can make
ming pools and children’s water help with this critical step. In any to ensure healthy plants and water
toys. event, think about who will use conservation.
When installing a new landscape, your landscape (adults, children, Organic matter such as compost,
there are several things you can do pets), how the landscape will be shredded bark, or peat adds nutri-
to reduce the amount of water it used (formal entertaining or infor- ents, increases the soil’s ability to
will need in the future. Many of mally), and what existing elements absorb and store water, and
these suggestions are based on the you want to keep. increases air spaces in the soil. As a
concept of “xeriscaping,” a term In your design, group plants result, plant roots can penetrate the
coined in the 1980s to describe based on the amount of water they soil more easily and grow more
water-efficient landscaping. Key need. This will prevent you from deeply. In addition, water soaks into
steps to establishing a successful overwatering the drought-tolerant the soil instead of running off the
water-efficient landscape include: species and underwatering those surface.
• Start with a landscape plan. that need more water. For tree, shrub, and flower beds,
If you include hard surfaces such till 2 to 4 inches of organic matter
• Improve your soil. into the entire planting area rather
as patios or walkways, use perme-
• Select appropriate plants. able materials that allow water to than amending individual planting
• Get your plants off to a good soak into the soil. Examples include holes. This will create a better
start. stone and gravel. Another option is environment for root growth.
to grade the site so that runoff is Turfgrass grows well in most soil
• Choose the most appropriate types and rarely requires additional
irrigation system. captured or redirected into the
landscape where plants can use it. organic matter. As long as the
• Water wisely. existing soil is tilled to a depth of
Improve your soil 8 inches, turf should grow well. To
• Mulch.
prevent runoff, make sure the final
• Take care of your plants. Most new residential sites have
grade doesn’t slope steeply toward
very poor soil. During construction,
a road or sidewalk.
most of the topsoil is removed, the
Ann Marie VanDerZanden, Extension
Master Gardener state coordinator,
Oregon State University.

2. Select appropriate moist as the grass germinates, and Automated sprinkler systems are
plants the new lawn will need water especially prone to encouraging
Many sources list low-water-use almost daily at first. It’s much better waste. Studies show that people
or drought-tolerant plants, but the to wait until the rainy season or with automated underground
criteria used in developing these until you have adequate water irrigation systems use up to twice as
lists vary greatly. The most impor- supplies for irrigation. much water as those watering
tant thing is to select trees, shrubs, manually with hoses and sprinklers.
groundcovers, and perennials that Get your plants off to a The convenience of an automated
are adapted to your region’s soil good start system makes it easy to overwater
and climate. Choose healthy plants and plant because you pay less attention to
A good idea is to look for plants them correctly to get your water- your landscape.
that are native to your area. How- wise garden off to a good start.
ever, just because a plant is native Consult a nursery, your county Water wisely
does not necessarily mean it is Extension office, or reference books People waste water; plants don’t.
drought-tolerant. Likewise, many for planting instructions. All plants Landscape water loss typically
nonnative plants are well adapted to require supplemental water and occurs in two ways:
our region. In general, species some extra attention during the • Water is applied too rapidly and
native to Mediterranean climates first, and possibly the second, runs off the soil surface rather
are suitable for western Oregon. In growing season. See “Water than soaking into the soil.
eastern and central Oregon, plants wisely” at right for more informa- • Water is applied to bare soil
native to the high desert Rocky tion. surfaces and evaporates.
Mountain plateau make good
Applying the right amount of
choices. Choose the most water, at the right time, and in the
Most turfgrass species used in appropriate irrigation right way is the most important
Oregon have similar water require- system thing you can do to conserve water.
ments. Ecolawns are a low-water Wise watering involves applying
alternative to traditional turf. They water slowly, deeply, infrequently, Watering new trees, shrubs,
contain a mix of broadleaf plants and directly to the root system. As a and groundcovers
(clover, English daisy, and yarrow) result, water soaks into the soil If it doesn’t rain, most trees,
and grasses (generally perennial rather than running off the surface shrubs, and groundcovers benefit
ryegrass). Ecolawns provide many or evaporating. The type of water- from a once-a-month thorough
of the benefits of traditional turf, ing system you choose can make a watering during the growing
including recreation, dust and noise big difference in how efficiently season. The majority of tree and
abatement, and temperature mod- you water. shrub feeder roots (those that take
eration, but require less irrigation. Tree, shrub, and flower beds, as up water and nutrients from the
Note: It is very difficult to well as vegetable gardens, are most soil) are in the top 12 inches of soil
establish a new lawn during a effectively irrigated with drip or and extend as much as one and a
drought. The soil needs to be kept trickle systems. Some drip systems half times past the canopy diameter
have individual emitters spaced (Figure 1). To be most effective,
along a hose. Soaker hoses, on the apply water in this area. Saturate
other hand, slowly release water the area to a depth of 8 to 10 inches.
along their entire length. Another Figure 2 shows how long this will
option is a garden hose with a slow take with various soil types.
stream of water. You can use a drip system with
Sprinklers are much less efficient individual emitters or a soaker hose
because they lose water to evapora- laid throughout the area. Another
tion and apply water to areas where option is a garden hose with a slow
it is not needed. In some cases, stream of water. For larger trees and
however, sprinklers might be the shrubs, you will need to move the
only alternative. hose around in order to get good
coverage. This technique might take
several hours for large trees.
2 • Conserving Water in the Garden

3. Watering young lawns especially important with automatic and flower beds can significantly
How much and how often are the sprinkler systems. Repair or replace reduce water evaporation. Various
two biggest questions associated broken or damaged nozzles or types of mulch are available,
with watering newly established heads, ensure that the timing including organic mulches (wood
lawns. Newer lawns are less able to mechanism and rainfall shutoffs are chips, shredded bark, compost) or
withstand drought than well estab- working, and make sure you know inorganic types (lava rock, river
lished lawns. To maintain a lush, how much water is being applied. rock, landscape fabrics). In addition
green lawn, apply 1 to 11⁄2 inches of Check your system weekly and to reducing water evaporation,
water during the dry season. For adjust the days and run times as mulch can suppress weed growth,
most soil types, you should water needed to avoid overwatering. prevent soil compaction, and
one to three times per week in order moderate soil temperatures.
Water at night
to apply the right amount of water
or in early morning Take care of your plants
and avoid runoff from applying too
Less water is lost to evaporation
much water too quickly. No landscape is maintenance-
early and late in the day when
free. In order to enjoy the benefits
Water infrequently temperatures are lower, humidity is
from the hard work you put into
and deeply higher, and the air is calmer. The
designing and installing your water-
By thoroughly soaking the root disadvantage of watering before or
wise landscape, you must care for it
zone, you will encourage roots to after daylight is that you won’t see
properly.
develop deep in the soil, where your system operate, so you will not
moisture is held for a long time. know if you are overwatering or Pruning
These deep roots will help the plant underwatering unless you check New trees and shrubs generally
endure drought better. Frequent, your plants and soil periodically. need minimal pruning just to
shallow watering encourages plants remove diseased or broken limbs.
to develop shallow root systems, Mulch Mowing
which make them susceptible to Water is lost when it evaporates
New lawns need regular mowing
even moderate water shortages. from exposed soil. Applying a 3- to
(once a week during the growing
As the growing season 5-inch layer of mulch to tree, shrub,
season if necessary) to maximize
progresses and your plants develop
turf density and prevent excess
deep roots, you can gradually
evaporation from the soil surface.
lengthen the time between
See Table 1 for proper mowing
waterings.
heights for various types of grass.
Maintain watering Mow at the upper end of the range
equipment to encourage maximum root
To maximize efficiency, keep development, which will slightly
equipment in good shape. This is improve drought tolerance. (See
Table 1, page 4).
It usually is not necessary to
dethatch or aerate a new lawn until
its second year. (See EC 1018,
Removing Thatch and Aerating
2 hours 4 hours
1 in Lawns, for more information.)
4 hours 8 hours
2 in Dethatching and aerating estab-
6 hours 12 hours
3 in lished turf will help it develop a
dripline 8 hours 16 hours deeper root system and make it
4 in
10 hours 20 hours better able to withstand drought.
5 in
12 hours 24 hours
6 in Fertilizing
Sandy loam Clay loam Proper fertilizing can conserve
main feeder Figure 2.—Infiltration rates for sandy water. During a water shortage,
root zone
loam and clay loam soil. Silt loam soil reduce or eliminate fertilization of
Figure 1.—The feeder roots extend to absorbs water at a rate between these trees and shrubs. As a result, the
11⁄2 times the diameter of the canopy. two extremes.
New Landscapes • 3

4. Table 1.—Mowing height We offer discounts on orders of 100
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ing these publications.
plants will grow more slowly and Additional related publications will Conserving Water in the Garden:
use less water. be available soon. Check our Web site Caring for an Established Land-
Fertilize your lawn in April to (eesc.orst.edu) for new titles! scape.
maximize root development and To order copies of the above
publications, or additional copies of Conserving Water in the Garden:
enhance general plant vigor. Apply Growing a Vegetable Garden.
this publication, send the complete title
1 to 11⁄2 lb N/1,000 sq ft. If severe and series number, along with a check El Riego en Los Huertos y Jardines
drought develops, avoid fertilizing or money order for the amount listed, (Watering Vegetable and Flower
during summer. Fertilize in the fall to: Publication Orders, Extension & Gardens), EM 8765-S.
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Deer-resistant Ornamental Plants,
EC 1438. 75¢
Summary
Gardening with Composts, Mulches,
With a little planning and work, it’s easy to save water in your
and Row Covers, EC 1247. $1.00
landscape. Keep these tips in mind:
Maintaining a Healthy Lawn in
• Select plants that are adapted to your growing region.
Western Oregon, EC 1521. $1.50
Plant Materials for Landscaping: A
• Group plants according to water use.
List of Plants for the Pacific • Know your soil type and improve its water-holding capacity.
Northwest, PNW 500. $2.50
• Mulch.
Removing Thatch and Aerating Lawns,
EC 1018. No charge. • Select an efficient watering system.
Selecting, Planting, and Caring for a • Understand how and when to water.
New Tree, EC 1438. $2.00 • Keep your irrigation system in top working order.
Southwestern Oregon Tree Selection
Guide for Coos, Curry, Douglas, Drought cycles will continue to occur, and Oregon’s
Jackson, and Josephine Counties, increasing population will strain already limited water supplies even
EC 1505. $5.50 more. Planning now for the future of your landscape is an important
Sustainable Gardening: The Oregon-
and environmentally sound decision to make.
Washington Master Gardener Using water wisely benefits everyone!
Handbook, EM 8742. $20.00
© 2001 Oregon State University. This publication may be photocopied or reprinted in its entirety for noncommercial purposes.
Produced and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Extension work is a cooperative program of
Oregon State University, the U.S. Department of Agriculture, and Oregon counties. Oregon State University Extension Service offers
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Opportunity Employer.
Published May 2001.