Irrigation 101: Back to Basics

Plants or objects such as this boulder can block sprinklers, leaving dry patches on the other side.

Few elements surpass water on your plants’ list of requirements. While some plants aren’t terribly picky about their watering schedule, some are more exacting and dislike irrational irrigation choices. The added complications of drought and water restrictions are enough to make your head spin. Can’t we simplify and pop outside to water whenever there’s nothing interesting on television?

Besides the rampant overwatering this would cause, we would be robbed of the opportunity to become better acquainted with the needs of our foliaged friends. Their first self-affirmation will likely be that they have genetically hardwired watering needs independent of television programming. Self-affirmation number two will be that opposites do not attract; mixing high- and low-water plants makes for poor relationships. Meeting the needs of one will inevitably sacrifice the other.

In the past, guesswork was the home gardener’s method of choice for grouping plants. Times have changed, especially with tight water budgets calling for more informed choices. Fortunately, the UC Department of Agriculture and Natural Resources (UC ANR) has conducted research that groups plants into high, medium, low, and very low water needs. These are further divided into the six major climates of California. This information is available on a searchable database at

Irrigation is much more efficient and effective when all the plants on a circuit (AKA “valve” or “station”) need the same amount of water. You may need to do some “editing” of any mismatched planting beds before going on to the next major part of good irrigation, which is a well-designed and functioning system.

There are many different kinds of irrigation, but we can simplify a little by dividing them into two basic categories: drip and spray. Turf grass is almost always irrigated by spray; the trick is to get even coverage and apply water in the right quantity and frequency. When designing a system, make sure the spray of one head reaches to the next head, called “head-to-head coverage” in irrigation lingo. This is important because the area immediately around sprinkler heads gets most of the water, while the outer two-thirds of the spray area get less. To prevent dry patches, overlap the spray areas for even water distribution.

Avoid playing “hope and poke” with your irrigation timer by gathering information. Observe the sprinklers in action and make appropriate repairs or adjustments. Check to see how long the sprinklers can run before water starts puddling or flowing onto sidewalks. Determine the output of your sprinklers by performing a catch can test (see the following website). A handy tool for irrigation scheduling and general lawn care is available on the UC Guide to Healthy Lawns website at

Both drip irrigation and spray can be used on ornamentals and edibles, though drip is usually recommended wherever possible because of its efficiency rate of up to 90%. Drip systems consist of flexible tubing that runs above ground, delivering water in drips that infiltrate slowly to prevent run-off. Like spray, drip irrigation systems must be properly designed and installed to be effective. In addition, they require more frequent inspections, especially if the system is subject to wildlife, pets, or children. Regular inspection of the lines and emitters will help ensure that dead plants are not the first indicator of chewed lines or an emitter that has been knocked out of place by a game of dodgeball.

Water conservation is another important component of your irrigation system. Watering deeply but infrequently is better than daily, shallow watering, which forces plant roots to grow at the surface rather than deeper in the soil where they become more drought-resistant. Organic mulch (e.g. bark) placed on the soil surface reduces evaporation and feeds the soil microbiome, all of which makes for healthier plants.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website:







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