Watering the Landscape & Garden

We are quickly approaching summertime weather conditions as the temperature steadily climbs a few degrees every day or two. Unfortunately, it looks like we’ll be going into summer on the very dry side. Which means we will need to water landscape to minimize drought stress, or at least keep things alive.

Of course, using more irrigation water means our water bills will dramatically increase. And increased usage can put a strain on some community’s water resources and ability to deliver water to maintain critical infrastructure functions during prolonged droughts. So, it makes sense to use this most precious resource wisely and efficiently.

Knowing when to water and for how long is fundamental to maintaining a quality landscape that is also water efficient. Newly planted trees and shrubs need more frequent watering from the time they are planted until they are well-rooted. During this establishment period, plants can be gradually weaned to a smaller amount of water. Proper weaning develops deep roots and makes plants “drought enduring”.

Of the tremendous amounts of water applied to lawns and gardens, much of it is never absorbed by the plants and put to use. Some water is lost to runoff by being applied faster than the soil can absorb it, and some water evaporates from exposed, unmulched soil before it can be used by the plant. But the greatest waste of water is when too much is applied too often. More plants are killed by too much water than by too little.

Many lawns receive twice as much water as they require for a healthy appearance. It is best to not water by the calendar, for example, once a week. Rather, it is better to water when the plants need watering. Most gardeners can readily recognize lawn stress signs due to lack of water, such as wilting and going “off color”. The key to watering lawns is to apply the water as infrequently as possible, yet thoroughly so the soil is wetted at least 5 or 6 inches deep.

As with lawns, trees and shrubs should be watered infrequently as possible, yet thoroughly. Most established trees and shrubs will benefit from a twice a month thorough watering during the growing season in the absence of adequate rain. Normal lawn watering is no substitute for thorough tree and shrub watering.

Types of Systems. There are two types of irrigation systems used in landscapes — sprinkler and drip irrigation. With an Earth-Kind landscape, it is recommended to use a combination of both systems in watering turfgrass, trees, shrubs, ground covers, flowers, and vegetable gardens.

Sprinkler irrigation is the most commonly used method of watering. The two kinds of sprinkler irrigation systems are the hose-end sprinkler and the permanent underground system with raised sprinkler heads.

The differences in these two sprinkler systems are in the cost, convenience and efficiency. Permanent, sprinkler systems are much more expensive than hose-end sprinklers. Yet the permanent system is much more convenient and can be much more efficient in applying the water. The major advantage for sprinkler irrigation is in lawn watering.

However, there are some potential drawbacks to sprinkler irrigation for shrubs and flowers. Sprinklers wet the plants, as well as the soil. Water which remains on a plant through the night increases disease susceptibility. Therefore, sprinkler irrigation should be used early in the day to allow time for the plant leaves to dry before nightfall.

Another disadvantage of sprinkler irrigation occurs on windy days. Watering in as little as a five mph hour wind will distribute the water unevenly over the area and result in a great deal of evaporation.

Perhaps the most efficient way to water the home landscape is with a properly designed and well-maintained drip irrigation system. Drip irrigation slowly applies water to soil. Water flows under low pressure through emitters laid alongside the plants.

Water applied by drip irrigation has little chance of waste through evaporation or runoff. The water is applied directly to the plant’s root zone. This also eliminates waste from applying water to unplanted or weedy areas.

Irrigation requirements vary according to plant species, soil type, rainfall, and temperature. Established, well-adapted plants require less frequent watering than newly planted trees and shrubs. A minimum length of time to operate a drip irrigation system is three hours. However, it may take six to 12 hours to thoroughly wet the root zone of an established large shrub or small tree.

Cover the drip system with mulch to hide the tubing from view and add to the life expectancy of the system.

When properly utilized, irrigation systems give plants a sufficient amount of water without waste. Ideally, planting areas with a higher water requirement can be watered separately from lower-water-use plants by zoning the irrigation systems.

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