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New Mexico State University

New Mexico State University

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Protect Plants from Drought, But Don't Xeriscape Just Yet

ALBUQUERQUE -- Signs of water stress are showing up in trees and shrubs throughout New Mexico, but contrary to popular belief, it's probably not the right time to replace water-guzzling vegetation with xeric plants.

Curtis Smith, horticulture specialist with New Mexico State University's Cooperative Extension Service, pulls down a dead limb on an apple tree in a Northeast Heights backyard in Albuquerque. Dead limbs are one indicator of water stress in trees. (06/21/2002) (Courtesy Photo by Kevin Robinson-Avila)

"Severe drought is encouraging gardeners to put in lots of water-wise plants, but a drought year is really not the right time to install a large Xeriscape," said Curtis Smith, horticulture specialist with New Mexico State University's Cooperative Extension Service.

"Even xeric plants need additional water to become established, which means frequent irrigating in the first year or two after planting. But there's not enough water available for that, especially in places like Santa Fe or Las Vegas where severe watering restrictions are in effect."

Homeowners can plant a few slower-growing xeric plants this season to get a head start on a Xeriscape, but time and money would best be spent on landscape planning and design, Smith said.

"The drought offers an opportunity to learn about plant material that's better adapted to our semiarid climate and soils," he said. "We can develop a colorful, uniquely New Mexican landscape with plants that require little water. Now is the time to plan for that. When the reservoirs are full again, put those plans into action."

In the meantime, Smith suggests taking steps to protect existing trees and shrubs from drought damage.

Homeowners should look for signs of water stress to determine the vegetation that is suffering most.

"Some trees are doing just fine, but there are lots of dead and dying trees out there," Smith said. "The bad news is, some of those trees are not going to make it. We need to let them go and remove them. The good news is, many of them can be saved."

Telltale signs of damage are leafless branches and dead or dying limbs. Other problems are browning of leaves, known as salt burn, and generally sparse leaf development throughout a tree.

"A lot of trees are dying backward from the tips of branches inward and downward toward the living wood," Smith said. "I've seen a lot of trees with little tufts of leaves appearing in patches instead of full leafing. These are clear signs of water stress."

With shrubs, roses and hedges, look for dead twigs, leaf damage and flowers that dry before fully opening, he said. Trim away all the dead areas, leaving only healthy branches and twigs.

"Dieback is an open invitation for insects like borers and bark beetles," Smith said. "We need to remove the dead branches and twigs so insect populations don't build up and begin attacking the healthy parts of plants."

Homeowners also need water efficiency to better moisten plant roots. Soil compaction is often a problem, especially in heavily trodden urban areas.

Smith suggests loosening soil with a rototiller or spading fork to let water seep easily downward. When aerating soil, add organic matter to help plants grow, but be sparing with manure because of its high salt content, which can damage plants, Smith said.

Use lots of mulch to cover soil surfaces around all trees and shrubs. Mulch reduces evaporation and erosion, and moderates temperatures to keep soil cooler in summer and warmer in winter, he said.

Organic mulch includes wood chips, bark, straw, and grass clippings. Rocks, gravel, sand and porous plastic can also be used.

Soil types affect how long and often to irrigate. Smith suggests pushing a screwdriver or stick into soil after watering to measure moisture depth and see how long it takes to water particular soils. Moisten lawns at least 8 inches in depth. Moisten trees and shrubs 2 to 3 feet deep.

Finally, connect drip systems to faucets that are separate from sprinklers. "If both are connected to the same valve and the system runs for 20 minutes, shrubs and trees will receive less than one-half gallon of water, and that's not enough," Smith said.