Answer: It's hard to determine exactly what is happening to your trees online, but I suspect it has to do with improper watering techniques. (The biggest cause of death to landscape plants in the arid Southwest is improper watering.) It sounds as if your cedar trees are in your grass landscape and receiving the same irrigation. Irrigation that works for lawns is generally bad news for landscape plants. Here's some background info:
Desert soil and water both contain considerable salts, which can accumulate in the root zone over time. This salt buildup forms where the water stops penetrating. If you ?sprinkle? plants lightly and frequently (as you would for lawns), salts will build up in the top layers of soil and damage or kill the roots. This excess salt accumulates in the leaf edges, where it kills the tissue and the leaf dries out and turns brown. Browning usually occurs on the old leaves first.
It's important to water trees and shrubs deeply and slowly. At least once a month, water deeply enough to "leach" or push salts well below the root zone.
Use a soil probe (any long, pointed piece of metal or wood to poke into the soil) to check how far water has penetrated. The probe moves easily through moist soil, but stops when it hits hard dry soil. For trees, water should reach about 2-3 feet deep. There are numerous variables involved for watering schedules, such as type of soil, how fast or slow it drains, sun and wind exposure at your site, temperature, age and condition of the plants and much more. In your area, established trees could probably be watered about once a month in winter, once every two weeks in summer, assuming that you are giving deep, thorough irrigations below the root zone. I hope this info helps.
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