The importance of landscape irrigation

By Dan Eskelson
Reader Columnist

Landscape irrigation is a term to describe the artificial application of water to a landscape. To keep your gardens thriving requires the careful management of irrigation practices. The following tips will help.irrigation-WEB

Studies have indicated that plants utilize root zone water most efficiently during morning hours, so try to irrigate very early in the day. Much of the water applied during the heat of the day is lost to evaporation – thirty percent or more is lost from overhead irrigation. Watering during evening or nighttime hours may be acceptable, but plants which are susceptible to fungus diseases will suffer from being damp for the extended overnight period.

The general rule is to water as deeply and as infrequently as possible. Watering deeply and infrequently encourages the plant to develop a deep root system, which in turn increases drought hardiness, since the soil dries from the top down. Frequent, light irrigation encourages a shallow root system which will suffer from every dry spell.

Duration of watering time depends on the soil—and the crop. In an “average” loam, one inch of irrigation will penetrate 12 inches. In a sandy soil, penetration will be deeper, and in a clay soil, not as deep. For established shrubs in the average loam, a thorough, deep irrigation once per week should be adequate during the growing season. Since clay soils hold water longer, care must be taken not to over water, which will exclude necessary oxygen from the soil profile.

Plants have different water needs. For instance, the red-twig dogwood (Cornus stolonifera) will thrive in a soil that is always damp—but many other plants require a thorough drying between irrigations—so if at all possible, group plants of similar water needs together.

For lawns, there is no substitute for overhead irrigation. For shrub beds, vegetable and herb gardens and fruit trees, drip irrigation is far superior—the plants receive a slow, metered supply of water, which is not as susceptible to losses from evaporation and overspray.

Because the water is applied slowly on or near the ground, there should be no waste from runoff and little or no loss to evaporation. You position the emitters to deliver water just where the plants need it; you control penetration by varying the time the system runs and/or the emitters’ delivery capacity (rated in gallons per hour).

Besides water conservation, the chief advantage of drip systems is flexibility. You can tailor the system to water individual plants by providing each with its own emitter(s); or you can distribute water over larger areas with microsprays.

A standard layout might include hookups to two or more valves and many kinds of parts. Because the lines are above ground (they’re easily concealed with mulch) and are made of flexible materials, changing the system is simple: just add or subtract lines and emitters as needed.

Water savings from drip irrigation can easily be 50 percent or more versus traditional sprinkling. See for good drip information and products.

Keep in mind that sprinklers and drip emitters apply water at different rates (measured in gallons per minute and gallons per hour, respectively). It’s best to put sprinklers and drip emitters on different irrigation valves. Also, a drip system requires a pressure regulator to limit pressure to the system and a filter to insure that the tiny emitter openings do not clog.

Our ongoing drought and global climate change has demanded a reevaluation of how we use one of our planet’s most valuable resources. Take care to fine tune your irrigation system for efficiency and conservation.

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