Issue: March 25, 2006
Landscapes and the drought
Question:
My city has imposed very strict outdoor watering restrictions. I'm worried that my landscape will die! What can I do?
Answer:
In some situations, the answer is to carefully choose which elements in your landscape you can save, and accept the fact that some other parts of the landscape will die. Also, don't plant new plants that need extra water until they are established in the landscape.
Trees are a valuable part of a landscape and can be watered sufficiently to keep them alive under the conditions of most restrictions. Since it takes many years to establish a tree, trees should be a high priority for saving. If the tree is old and in poor health, you may decide that it should be removed and can be sacrificed, but this is probably not the year for you to try to replace it.
Shrubs may be second on your "save list." You may not be able to save all your shrubs, so consider the location and function of each shrub in your landscape to determine which ones you can save. You may have some that have sentimental value and are important to you. Those near the entry to your home and those that provide privacy are also ones to consider saving.
Daylilies, peonies, irises, and other herbaceous perennials may also be high priority plants. These will take less water than the trees and shrubs because they are smaller plants and use less water.
Lawns and plants not often seen from a close vantage point (far back in the yard or in a side yard) may be the ones with lowest priority. Annuals and lawns can be reinstalled in a single year if they are allowed to die. Trees and shrubs take from several to many years to develop in the landscape. That is the reason for this order of priority. You may wish to modify these priorities according to your needs and preferences.
There are several methods to maximize water efficiency when trying to save your high priority plants. The first is use of mulch. Water evaporates more slowly from soil covered by a thick blanket of mulch. If the mulch is organic (wood chips, bark, straw, etc.), it is important to pull the mulch aside to avoid letting the mulch absorb any irrigation water before it reaches the soil. If you irrigate with a hose or drip irrigation emitters, place them below the mulch for the same reason. Follow the requirements of your restrictions (only watering once a week or whatever is mandated). Trees may be watered once a month (for maintenance) or twice a month (for healthier trees and growth) if they are watered so that the soil is moistened to a depth of two to three feet with each watering. Shrubs should be watered once every two weeks to moisten the soil to a depth of two feet. This requires a large quantity of water, but it fits within the restrictions currently imposed in several New Mexico communities. To conserve water, don't irrigate in areas where the trees and shrubs do not have absorbing roots. That means you should not apply water at the base of the tree trunk or at the very base of the shrubs. Apply water at the dripline of the trees and shrubs and outward for a few feet (depending on the size and spread of the root system). For maintenance (just keeping the trees alive), it is not necessary to irrigate the full extent of the absorbing root system.
Shrubs and herbaceous perennials may be irrigated with gray water and water collected while waiting for hot water to reach the bathtub, sink, and lavatories. Don't waste this cold water while you wait for the hot water. Collect it in buckets and take it to the smaller plants. Used bath water and hand washing water can also be collected for use outdoors even if it contains some soap. These sources of water are not sufficient for trees but will be adequate for small shrubs and the herbaceous plants.
It is important to conserve water, but it is also important to keep as much of the landscape alive as possible.
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!