Fall and Winter Watering - January 3, 2001
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County

After last year's dry/warm winter, a meager monsoon season, and a long dry spell since early November, I better start talking about winter watering. Several residents contacted the Cottonwood Cooperative Extension office about dead pine trees and I suspect many of the pest problems we saw were drought induced. Let's prepare ourselves for drought this year by irrigating our trees properly during the winter.

During fall and winter, we often experience dry air, little precipitation, and wide daily temperature fluctuations. This is made worse when the weather is drier and colder than normal. Trees, shrubs, and turf may be damaged if not given supplemental irrigation. As a rule of thumb, evergreens need more supplemental water than do deciduous ones.

Long, dry fall and winter periods can result in death or injury to plant root systems. Affected plants may appear perfectly normal and resume growth in the spring utilizing stored energy reserves, only to weaken and die in late spring or early summer when the stored energy runs out. Weaken plants are also more susceptible to insect and disease problem later.

Green leaves need water to facilitate photosynthesis and respiration. To supply themselves with water, leaves are constantly pumping water (transpiring) from the soil into the roots then through the stem into the leaves. The excess water is lost from the leaves and goes into the atmosphere. Plants without winter foliage do best when there is some soil moisture, but their requirement is much lower.

Recently planted trees and shrubs are especially susceptible to damage from lack of adequate soil moisture. Once a healthy root system is established, they will be less susceptible to drought. Even xeriscape (drought tolerant) plants can benefit from infrequent winter irrigation. In addition, plants with shallow root systems require greater or more frequent winter irrigation. Some of these are pine, spruce, juniper (non-native types), Euonymous, and Oregon grape.

My recommended method of watering where no irrigation system exists is the soaker hose: the black, rubber, porous type. These are relatively inexpensive and can be placed semi-permanently or moved from place to place depending on individual circumstances and needs. They put the water down slowly and close to the soil.

Apply irrigation early in the day so it can soak in before possible freezing occurs during the night. If significant amounts of water freeze at the base of a tree or shrub, it can result in bark damage. For established landscape trees and shrubs, four to six weeks should be the maximum amount of time between irrigations. Of course this varies with soil texture and species.

On established trees and shrubs, place the hoses in a circle starting about four or five feet from the trunk and coil the soaker hose around the tree leaving about two feet between each coil. Leave the hose running until water soaks in to a depth of about two feet. This can be checked with a metal probe or long screwdriver.

To encourage newly planted trees (planted in that location for two years or less) to develop more extensive root systems, water from the trunk to at least one foot beyond the drip line of the canopy.

I have two motives in writing this column. First, for those of you that lost (or almost lost) a favorite tree or shrub last year, this should increase your chances of success in the future. Second, by encouraging everyone to irrigate, it should increase our chances of getting some rain. Hey, on that note, why don't you wash your car too? All goofiness aside, I hope you all have a wonderful gardening new year!

The University of Arizona Cooperative Extension has publications and information on plant selection and soils. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. The Yavapai County Cooperative Extension web site is http://ag.arizona.edu/yavapai/.

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Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr. #C
Prescott, AZ 86305
(928) 445-6590
Last Updated: March 15, 2001
Content Questions/Comments: jschalau@ag.arizona.edu
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