Landscape Watering Refresher

Bonnie Nowicki

Our Sonoran Desert is characterized by low humidity and little rainfall—only 7 to 14 inches per year. Most of the plants in Quail Creek yards need supplemental watering. Landscape plants suffer more from problems related to watering than from any other cause. Landscape watering can be a confusing topic, so I hope these guidelines are helpful.

Most Quail Creek yards use drip irrigation systems. Watering early in the day is definitely recommended. It gives plants plenty of time to dry and minimizes water loss from evaporation. It’s also easier to check for leaks. Please realize that a drip system with a one gallon per hour (1 GPH) emitter and a 15-minute runtime puts out only one quart of water. Shallow watering is a big problem. It encourages roots to stay close to the surface of the soil and builds up salt—that white, powdery film on the soil surface. Salt burn may show up as yellowing leaves or brown leaf margins. Drip systems must run long enough for water to penetrate to the appropriate depth.

The goal is to water the root zone where most feeder roots are found. This area is within the top one to three feet of the soil. Position your drip line emitters around the outside canopy edge of the plant, not the inner circle. Water small perennials and annual flowers and vegetables to a depth of one foot, shrubs and large groundcovers to a depth of two feet, and large shrubs and trees to a depth of three feet. Use a thin, metal soil probe or sharpened wood to test the depth. It will be difficult to push when it reaches dry soil. Plant type, size, and soil type all affect watering frequency. Clay soil needs more water to wet the root zone, but applied less often.

Modify irrigation systems as plants grow and use a variety of emitter sizes when a drip zone has different plants, such as two fruit trees (4 GPH emitter), one shrub (2 GPH emitter), and three small plants (1 GPH emitter). Set timer for a 2-hour run. Here’s a summer watering schedule guideline for established plants in silty clay soil using 2 gallon-per-hour emitters, running for about three hours for trees and two hours for shrubs. Trees, seven to 14 days between watering; shrubs, five to seven days between watering; and flowers, vines, and groundcovers, two to five days between watering.

Hopefully, this year’s monsoon season (June 15 through September) will bring some relief to our stressed landscapes. Stay positive, and happy watering.