Watering Tips for Lawns, Vegetable Gardens and Trees

by Rex Morris, El Paso Master Gardener

Watering Lawns – If you have a subsurface irrigation system for watering your lawn, it doesn’t get better than that. These systems provide good coverage, low water loss due to evaporation, and reduced runoff onto streets or sidewalks. However, detecting leak locations or other problems can make repairing subsurface systems a challenging job for a homeowner. Drawbacks of subsurface systems are that they are expensive to install, easy to damage, and difficult to maintain or repair.

Many people have pop-up sprinkler irrigation systems. A well-designed system should provide water to an entire lawn, but there will be some overlap. A pop-up system requires frequent checking. Broken or damaged sprinkler heads, twisted sprinkler heads, and partially clogged sprinkler heads will all put the water where it doesn’t belong.

Other people use sprinklers with attached garden hoses to water their lawns. In general, the larger an area covered by a sprinkler, the finer the water stream and the longer the time the stream passes through the air. This means that the amount of water that evaporates into the air is greater under windy conditions and water doesn’t go where planned. If possible, use more sprinklers and have each one cover less area.

Water your lawn early in the day when the air temperature is cooler. Just before or right after dawn is best when there is usually little wind and city water pressure is high. A good rule of thumb for lawns in the summer is to apply a total of one inch of water per week.

To determine how much water is required to apply one inch, place multiple empty tuna or cat food cans throughout the lawn and turn on the water. Measure the water depth in the cans to determine the time required to apply one inch. If water begins to run off the lawn area before achieving one inch, note the time the water was running, wait one-half to one hour to allow the water to soak into the soil, and then restart the water until an average of one inch of water is measured in the cans.

Using these collected data, adjust your watering times during the week to apply a total of one inch per week to match the type soil your grass is growing in. For very sandy soil, water three times a week to achieve a combined one inch per week. For less sandy or clay soils, water twice a week to apply the one inch per week.

Lawns will require less frequent watering in the late fall and early spring. During the winter months, water once a month to keep the dormant roots moist. If your lawn irrigation system is fully or partly automated, remember to change the length of time and frequency of irrigation to reflect changing seasonal water requirements.

TIP: Cycle and soak methods of irrigation are helpful when the irrigation system applies water faster than the ground will absorb or if there is runoff on sloping areas.

To increase water absorption and avoid runoff in flat and sloping areas, irrigation stations can be set to run several short times instead of one long time.

Read this article on Cycle and Soak to learn more.

Watering Vegetable Gardens – Vegetable gardens are best watered using low-volume/drip/trickle irrigation systems. Low-volume or drip irrigation systems apply water at the rate of a few gallons per hour, unlike lawn sprinklers that apply water at the rate of gallons per minute. Unlike sprinklers, these systems only irrigate a limited area through emitters connected to quarter-inch tubing directing water directly to the area beneath the plant.

Drip systems apply water near or on the ground at a rate slow enough so that the water filters into the ground without running off the surface so less water may evaporate. The low rate also nearly eliminates many plant diseases sometimes caused by hand or overhead watering when the stream of water hits the soil and then, carrying spores or organisms, splashes onto plant leaves.

Pressure compensating drip emitters (“PC” emitters) are usually preferred for pressured watering systems because they ensure a more consistent water flow if water pressure fluctuates. Check the manufacturer’s recommended operating water pressure range for the emitters and install a water pressure regulator to prevent damage to the system. Emitters used with a gravity-flow (i.e. rain barrel) or unpressured water system should be the ‘flag’ type which that operate efficiently at lower water pressure.

Select emitter types of the required rate per hour (1 gal/hour, 2 gal/hour, etc.) and install the number of emitters based on the need of the plants. All drip emitters are subject to clogging. The installation of an efficient inline filter will help to reduce clogs.

Vegetables grow and produce best when growing in equally moist (not saturated soil). Plan to water for one hour, then monitor the frequency and length of watering times depending on the season to ensure you neither water too little nor too much.

Water in the cooler early mornings and use mulch help to ensure that sufficient soil moisture is available to the root systems during the heat of the day.

Watering Trees – Trees are best watered less frequently than lawns, but for a longer period each time to permit water to deeply penetrate the soil surrounding the root system. The soil surrounding a tree should be soaked out to (and a little beyond) the furthermost edge of the leaf canopy (the drip line) until the water has infiltrated the soil to a minimum depth of eighteen to twenty-four inches. Determine the depth of water penetration into the soil by seeing how deeply a metal rod or probe may be inserted into the ground without needing to hammer it into the ground.

Desert willow tree w_drip irrigation

Credit: Desert Willow Tree with Drip Irrigation by Marlene Stalker, El Paso Master Gardener

Deep watering of the entire root system encourages deeper root growth. This makes it less likely the roots will push up sidewalks and foundations, increases resistance to drought, and provides better insurance against the tree toppling by strong winds. Deep watering wands are available for this purpose.

Since newly planted trees may require up to three years to become fully established with a root system capable of sustaining it throughout the year, young trees will usually need more frequent deep irrigation, especially in the summer, until they are fully established.

Once established and depending on the soil and tree type, watering frequency in the summer can depend on the temperature. In the hottest weather, water trees deeply once every one to two weeks. More moderate summer temperatures call for watering every three weeks. Water dormant trees every three to four weeks starting in the fall through mid-spring. You can use your soil probe to determine the soil’s dryness and water when your soil probe won’t penetrate the ground more than three or four inches.

The area next to the trunk of established trees should not be irrigated to help prevent disease and rot. Water out at the drip line area instead.

TIP: Planting a tree within or next to a lawn will place the tree in competition with the turfgrass for adequate moisture. Irrigate the tree separately to develop a deep root system, otherwise a very shallow tree root system may develop which would not provide adequate drought resistance.

Read Help Your Tree Survive in El Paso to learn more about watering trees and other tree care best practices.

Roger “Doc” Stalker, an El Paso Master Gardener, contributed to this article.


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