Issue: November 10th, 1997

Winter watering

How often should I water my landscape plants during the winter? Can I stop watering until spring?

Here in New Mexico whether or not to water depends on the weather and on the plants in your landscape. If the soil remains moist due to rains and snows, little irrigation will be required. But, in New Mexico, the winters are often dry enough that the soils will dry for significant periods of time in the winter. In that case, the decision to water depends on the plants. Plants adapted to dry winters, those well adapted to xeriscapes, will need no water. Some plants native to dry environments, such as the desert willow, prefer dry conditions during the winter. Plants native to moist environments will need supplemental irrigation during these dry periods.

For many of the trees and shrubs grown in our landscapes, the most critical time for irrigation is in the late winter as the buds begin to swell. This may be more than a month before growth begins, and this is the time when small absorbing roots form for many plants. These roots need moist soil to grow, survive, and do their job absorbing water and nutrients. If the soil is too dry at the time these new absorbing roots form, the roots may die and the plant will have a difficult time beginning growth in the spring. Other times in the winter, however, water is also necessary. Water is lost through twigs and stems, even when leaves are absent. This water must be replaced. Evergreens which have leaves through the winter lose even more water which must be replaced to keep the plant alive.

When the soil is frozen, it is difficult to successfully irrigate plants. Before the soil freezes and during warm periods when the soil thaws, it is possible to irrigate. Fortunately, when the soil is cold, the water is lost less rapidly and the plants need less water.

When to prune trees

Is it okay to prune my trees now or should I wait until sprng?

Now that the trees are dormant, you can begin pruning your deciduous trees. You can prune deciduous trees until the buds begin swelling in the spring. However, I would wait until spring, just before growth begins to prune evergreens such as junipers and pines. Pines, spruce, and most evergreens require a different type of pruning than deciduous trees.

At this time of the year, you can do more extensive pruning than when the trees are not dormant. It is important to avoid excessive pruning. Young trees which are vigorously growing may be pruned to remove up to one-quarter of the branches and twigs. Older trees should be pruned much less. Old trees which are not growing much should only be pruned to remove dead and diseased wood. Please remember that "topping" trees weakens them and is poor pruning practice.

When pruning, it is important to make the pruning cuts at the appropriate location, not too close and not too far from the branch or trunk from which the branch being removed originates. Check with your local County Extension Office or in your local library for recent pruning information which explains "branch collars" and explains how to properly prune the trees.

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.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!