If you decide to decrease lawn watering, you should not discontinue watering trees and shrubs. They cannot go dormant during the growing season.
Trees and shrubs need moist, but not saturated, soil in order to grow well, resist insects, diseases and winter injury, and to produce flowers and fruit.
From early spring through August, apply adequate water to all woody plants. From September through mid-October, gradually withhold water to allow plants to "harden off." This reduces the chances of wood damage by early freezing temperatures or snowstorms. In mid-November, prior to the ground freezing, apply water liberally to allow water to reach and saturate the root area. This will help to prevent winter kill.
During the growing season, do not over-water. When you water, soak the soil approximately 12 inches deep. Wet the entire root area, which extends out to as much as three times the limb spread. Newly transplanted trees and shrubs need water more often than established ones. Adequate, but not excessive watering, results in healthy trees and shrubs.
For foundation and border plantings, you can use a sprinkler on the entire area or use soaker hoses or a trickle/drip irrigation system to prevent water waste.
Use of soaker hoses, trickle or drip systems allows water penetration to the root zone with minimum surface wetting and water waste. This can save 60 percent or more in water use.
A berm around the tree or shrub base may be filled with water for slow infiltration and percolation into the root zone.
Mulch materials placed over the soil around plants reduce evaporation and water runoff. Mulch also improves water penetration into the root zone and limits weed growth that also competes for water. Mulch may be organic (shredded leaves, bark, straw) or inorganic (gravel).
2 1/2-3 gallons of water once a week around a 6-to-8 foot plant can keep it alive during low water periods.
During hot, dry periods, water plants every 6 to 10 days. New plantings need water every 5 to 7 days.
Do not water foliage of fruit trees or deciduous trees. Watering encourages rust, blight and mildew diseases.
Uniform watering of trees and shrubs means better quality in fruit production.
Species such as green ash, caragana, Russian olive, lilac, cottoneaster, pines and Douglas fir are sensitive to excess water.
Evergreens can be watered on the needles and limbs and not be sun-scalded or burnt.
Use of landscape cloth mulch around ornamentals conserves water and discourages weed growth.