Irrigation Conservation for Trees, Shrubs, Gardens, and Lawn

Photo © Wandering Sagebrush

How much water does your garden need? How often should it be watered? What is the best way for the irrigation be applied? In many cases it is easier to overwater your plants than to not provide enough. Over-watering can actually damage or kill your plants, wasting water, and energy, and leaving you with higher water bills. Efficient and effective watering can be achieved through simple monitoring and correct application. In addition to conserving water, proper irrigation can encourage deeper root growth and provide healthier, more drought-tolerant landscapes. Below, we explore some basic guidelines on conservation methods to properly water trees, shrubs, gardens, and lawns.

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Photo © Kannan Muthuraman

Irrigation systems can waste water during transportation or through runoff, infiltration, or evaporation during delivery. Sprinklers, trench flooding, and many other types of water delivery systems can fail to deliver the right amount of water to the right spot. Ideally, water conservation requires secure delivery methods that apply irrigation directly to the root zone and adjusts for differences in seasonal watering requirements due to the specific species, the weather, and the plant’s maturity.

The Root zone is a critical area of plant’s vascular system. This is where new roots are growing underground to supply more water to the expanding shoots above. The canopy of a tree or shrub, or the vegetation of flowering plants, can block precipitation and sprinkled irrigation from reaching the roots directly underneath. The Root Zone extends beyond the drip line to help maximize the amount of water a plant can absorb. Providing water to this area, rather than directly at the base of the trunk, is a more efficient way to irrigate when conserving water.
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Photo © Dwayne Madden

Water, water, every… where?
It is crucial to match the irrigation equipment with the size, shape, and type of landscape being watered. Watering sidewalks, landscaping structures, or the walls of buildings is wasteful and all too common with many irrigation systems that are too large or inaccurate for their setting. Watering plant foliage is also wasteful and generally unnecessary as it simply evaporates or increases the risk of fungal pathogens that can be difficult to control. Applying the correct amount of irrigation to the base of each plant is the overall goal in efficient irrigation. Fortunately, there are many options for catering a delivery system to the design and needs of the landscape being watered.

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Photo © International Institute of Tropical Agriculture

Knowing when to water is another key to saving water. Plants have an optimal level of soil moisture at which their growth is most productive. Different species of plants, of course, will have different optimal soil moisture levels and providing this ideal environment will increase absorption by the plant, effectively conserving water and improving overall plant health. Proper timing of irrigation also increases absorption into the soil. Watering too often or too late may result in runoff due to wet, saturated soil or impenetrable, dry soil. There are a number of products available to monitor the moisture content in soil and doing so will give you more control over your water use as well as the health and productivity of the plants you grow. The soil moisture sensors, pictured above, provide constant readings at various soil depths.

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Photo © Arctic Wolves

Penetration into the soil is also important for watering efficiency. You want moisture to reach the root zone for immediate use by the plant but also to penetrate below the roots to promote downward root growth. If your irrigation method does not provide enough penetration into the soil, the roots do not seek deeper, longer lasting sources of water and may become reliant on shallow, recurring waterings–putting the plant at risk during dry spells. You can use a soil probe to determine the depth of moisture in your soil. These can be purchased or simply made from any type of thin, pointed, metal rod or a long screwdriver. The probe will be easily inserted into moist soil and will meet resistance when hitting dry soil.

Common types of Irrigation

Common types of irrigation fall into three categories -Surface, Sprinkler, and Micro-irrigation.

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Photo © Hanna 3232

Trench/Flooding: Possibly the oldest and most globally used method of surface irrigation which uses the surface of the ground to deliver water, usually along furrows, trenches, or contained in raised borders. Although this is a simple and low-cost method of irrigation it can be the most wasteful as a large percent of the water is lost to runoff, evaporation, and infiltration into parts of the ground where plants can’t make use of it. Recapturing and reusing runoff, leveling fields, and applying lower doses in short surges are a few ways farmers are working-on reducing waste. On a smaller scale, this method is similar to using a hose to drench your garden. Using the techniques above, leveling the ground and applying water in short bursts, will help conserve water.

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Photo © TNC@Will van Overbeek

Sprinkler: Another very popular form of irrigation, sprinklers deliver pressurized irrigation through a series of pumps, pipes, and nozzles. The benefits of sprinklers over surface irrigation includes improved conservation by allowing for greater control over the rate and amount of water delivery, limiting waste from runoff. Waste in a sprinkler systems comes primarily from evaporation and drift, up to 35% of the delivered water is essentially blowing away in the windopen_in_new. Proper timing, a lower nozzle height, and spray adjustments can help minimize this loss.

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Photo © Joby Elliott

Drip irrigation: Drip irrigation is the most used form of micro-irrigation and utilizes tubing and individual emitters to deliver water directly to the base of each plant. Emitters come in various forms and can regulate the rate of water released. Some are just a small hole located on the underside of the hose. This method of delivery requires a bit of set-up initially and some routine maintenance but is very efficient at transporting water and applying irrigation evenly and at a rate that can easily be absorbed into the soil, eliminating waste from runoff and evaporation.

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Photo © Your Best Digs

From watering a potted plant to irrigating a farm field, there are a few basic principles regarding the relationships between plants and their water use.

  • Plants will require more water during their growing season and less if they go dormant.
  • Proper root establishment will lead to more efficient water use.
  • Watering in the cool morning will aid in soil absorption, reduce evaporation, improve uptake and use by the plants, and allows the foliage time to dry.
  • Over watering can saturate the soil and reduce the oxygen available to the roots causing them to shut down and be unable to supply moisture to the plant.
  • Under watering will cause a plant to wilt, possibly collapsing the cell walls and causing permanent damage.
  • Regular, efficient watering will generally conserve more water in the long run than harsh restrictions that stress plants and may result in low production with similar irrigation.
  • Native plants, once established, will usually need less water as they are adapted to the local weather patterns. Additionally, they are a great choice when choosing resilient landscaping plants.

Here are additional watering tips to get the most hydration out of the least amount of irrigation.

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Photo © Mark Levisay

Garden beds
Whether you have vegetable gardens or ornamental flower beds you are likely to have a variety of watering requirements for different plantings. To save time and water, group your plantings with similar preferences for soil moisture. This usually coordinates well with shade and light requirements. Use of drip irrigation is best for vegetable gardens and flowerbeds because it delivers the right amount of water directly to the plants you want to water and none to the weeds you don’t want to grow. Run a separate line, each with its own shut-off valve, to each type of moisture area. A soaker hose is another form of drip irrigation that is easier to install and will still provide fairly precise and controlled irrigation.

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Photo © melissa b.

The use of a moisture sensor will help dictate the intervals between waterings and using a soil probe to check moisture depth will help ensure the duration of the watering period is sufficient to provide adequate penetration into the soil but not more than is necessary. Another simple technique is to watch for an “indicator” plant –one of the the first plants to lightly wilt as the garden becomes dry. As the seasons progress and plants mature, irrigation requirements will change and soil monitoring practices, such as these, can produce healthy and vibrant vegetation, save work, and are an important part of water conservation.

PRO-TIP

Weeds use water too. Remove them and mulch around your plants with shredded bark mulch, leaf mould, or newspaper covered with straw to keep weeds out and keep moisture in.

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Photo © CLO

Trees and shrubs
With deeper roots, taller shoots, and longer growing seasons, trees and shrubs have their own unique set of water requirements. In general, you will need to water less often but for longer periods of time to allow water to penetrate deep below the roots, encouraging the tree or shrub to grow deeper roots. In the spring and fall, evapotranspiration, the process whereby a plant’s water use transfers moisture from the ground to the atmosphere, is much lower than in the summer when hot, dry air increases this rate. If the roots can not reach a continuous source of water, signs of water stress will be evident and irrigation may be necessary. Ideally, watering trees and shrubs should take place right before water stress occurs. Use a soil probe during periods of drought to monitor soil moisture. Look for signs of water stress in the curling or wilting of leaves or, with coniferous trees, the browning and dropping of needles.

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Photo © Rory Finneren

Planting new trees and shrubs requires some diligent and attentive care. The root system will take time to become established into its new soil before it can be efficient at supplying enough moisture to the rest of the plant. Planting shrubs, trees, or any perennial in the Fall is ideal for successful establishment as the plant’s need for water is greatly reduced and the plant can use all of it’s resources to grow roots into the new soil. Be sure to check soil moisture often and water as needed, about once or twice a week, to maintain moisture at a depth of 18-20 inches. Efficient watering can be done through a slow steady trickle for 2-3 hours to penetrate deep into the soil without running off. A drip irrigation system or a treegator, or another type of watering bag, will apply irrigation at a consistent rate. Mulching around the base of the tree or shrubs will help provide an ideal environment for slow steady watering with little erosion or evaporation. Once established, however, new trees and shrubs will only need to be watered during periods of hot dry weather. Selecting native trees and shrubs will require less maintenance overall.

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Photo © Scott Denny

Lawns
Our most irrigated crop–lawns tend to require an immense amount of irrigation, regularly applied, to maintain the smooth green expanse we’ve come to expect. Most lawns are nonnative grasses that are outside of their normal growing range and may require more inputs than the local environment provides. These include fertilizers, pesticides, and heavy watering. Efficient irrigation of lawn is critical to prevent runoff which can contaminate other local water sources, adding to polluted waterways, and creating hazards in natural environments. Efficient irrigation of lawn requires a system that delivers an equal and adequate amount of moisture to the entire turf area and not beyond. Waste or damage occurs when the system is not designed correctly for the space or is not properly maintained.

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Photo © Russell Bernice

Lawns are usually irrigated using a form of sprinkler system. Ideally, one that sprays water evenly across the surface of the lawn at a rate that allows penetration into the ground without runoff and a large enough droplet size that does not evaporate or blow away in the wind. Automated residential irrigation systems tend to result in higher water use than non-automated systems but the use of monitors like soil moisture sensors, rain gauges, and soil probes have been shown to improve efficiency of time based or scheduled irrigation regimes.

Whether you use a sophisticated automated system or simply water the lawn with a sprinkler on the end of a hose, the same concerns for water conservation can be present for either method:

  • Water less and during the cooler times of the day. This will reduce evaporation and improve absorption
  • Know how much irrigation you need, how much you are getting from rain, and how much you are putting on. Measure the amount of water in inches over time.
  • Maintain the system: clogs or leaks, misplaced or poorly aimed sprinkler heads, and interference from bigger plants, trees, or new landscape features create inefficiencies.
  • Lawns can be made from warm season or cold season grasses. Learn to expect the difference in seasonal needs. Grasses in their dormant period may appear brown but will not need water to survive. Remember brown is not bad.

To learn more about lawn options, explore our Native Lawn articles.


Cool season grasses are green in the spring and all through fall, whereas warm season grasses will green-up as summer temps turn the heat up.

Reducing the amount of water loss from transportation and delivery of your irrigation, providing the right amount of irrigation to the right spot, and using efficient scheduling of manual and automated irrigation systems will provide the opportunity to conserve water resources while maintaining quality landscape.

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