Watering trees in winter

I planted several young trees this summer and have tried to be diligent in watering them. My question is, "What kind of watering schedule would generally be appropriate for the fall and winter months?" (The trees in question are Sycamore, Arizona Ash, and Chinese Pistache.)

In the fall and winter when temperatures decline and as leaves drop from deciduous trees, the rate that water is used by the trees decreases. We can reduce the frequency of watering at this time. Continue to apply the same amount of water with each irrigation, just apply water less often. The frequency with which you irrigate will depend on the age of the trees, the soil in which they are planted, and weather conditions. Remember that evergreen trees have retained their leaves and will need to be watered as well.

Young trees have less extensive root systems and should be watered every 14 to 20 days if there has been no soaking precipitation. Older trees, established for three or more years, can be watered every 20 to 30 days. The more frequent irrigation, 14 or 20 days depending on tree age, is required for trees growing in sandy soils which hold less water. Longer intervals may be allowed for trees in heavier soils containing clay. If the weather has been warm and windy, additional irrigations may be needed. If the weather is cool and there have been good slow, soaking, rains or snows, irrigations may be skipped. Check the soil to see if there is moisture several inches down. While you don't want the soil to dry totally, there is little reason to apply water while the soil is moist. In areas where the soil freezes, it is difficult to add moisture. In these areas, irrigate well before the soil freezes and when it thaws.

When irrigating trees, moisten the soil to a depth of two to three feet with each irrigation. This should then provide sufficient water to keep the soil moist for the intervals recommended above. Remember, a clay soil will hold more water than sand, so you must apply more water to moisten clay to the same depth than when watering sandy soil. Since clay soils absorb water slowly, you may have to irrigate very slowly or in several brief, repeated, irrigations to provide enough water to moisten the soil to the proper depth. Water applied too rapidly to clay runs off and does not accomplish your purpose.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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