Conserving Water in the Garden: Designing and Installing a New Landscape - Oregon State University
EC 1530 • May 2001 $1.00Conserving Water in the GardenDesigning and Installing a New LandscapeA.M. VanDerZanden Water is quickly becoming one Research has shown that theseof Oregon’s most critical natural water-saving guidelines can reduceresources. As the state’s population landscape water use by 60 to 80increases and urban areas expand, percent.water use and water rights arebecoming increasingly contentious Start with aissues. landscape plan Typically, about 30 to 40 percent A water-efficient landscape remaining soil is compacted byof urban water use is for outdoor begins with a plan. If you are heavy equipment, and constructionactivities. In addition to landscape familiar with the principles of rubble is buried. A soil test will tellmaintenance, 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 improvementand sidewalks, and filling swim- option is to hire a professional to is the best investment you can makeming pools and children’s water help with this critical step. In any to ensure healthy plants and watertoys. 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 towill need in the future. Many of mally), and what existing elements absorb and store water, andthese suggestions are based on the you want to keep. increases air spaces in the soil. As aconcept of “xeriscaping,” a term In your design, group plants result, plant roots can penetrate thecoined in the 1980s to describe based on the amount of water they soil more easily and grow morewater-efficient landscaping. Key need. This will prevent you from deeply. In addition, water soaks intosteps to establishing a successful overwatering the drought-tolerant the soil instead of running off thewater-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.
Select appropriate moist as the grass germinates, and Automated sprinkler systems areplants 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 peopleor drought-tolerant plants, but the to wait until the rainy season or with automated undergroundcriteria used in developing these until you have adequate water irrigation systems use up to twice aslists vary greatly. The most impor- supplies for irrigation. much water as those wateringtant 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 automatedare adapted to your region’s soil good start system makes it easy to overwaterand 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 wiselydoes 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 typicallynonnative 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 andnative to Mediterranean climates first, and possibly the second, runs off the soil surface ratherare 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 soilnative to the high desert Rocky tion. surfaces and evaporates.Mountain plateau make good Applying the right amount ofchoices. Choose the most water, at the right time, and in the Most turfgrass species used in appropriate irrigation right way is the most importantOregon have similar water require- system thing you can do to conserve water.ments. Ecolawns are a low-water Wise watering involves applyingalternative 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 benefitryegrass). Ecolawns provide many or evaporating. The type of water- from a once-a-month thoroughof the benefits of traditional turf, ing system you choose can make a watering during the growingincluding recreation, dust and noise big difference in how efficiently season. The majority of tree andabatement, and temperature mod- you water. shrub feeder roots (those that takeeration, 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 soilestablish a new lawn during a effectively irrigated with drip or and extend as much as one and adrought. 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
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 ofFigure 1.—The feeder roots extend to absorbs water at a rate between these trees and shrubs. As a result, the11⁄2 times the diameter of the canopy. two extremes. New Landscapes • 3