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Drought and Trees

As you drive through Phoenix and Tucson metro areas, you might have noticed the browning of needles of older pine trees this winter. It has been determined by local plant experts that this browning of pines is due to drought.  Arizona is now entering its 21st year of long-term drought. Coupled with the abnormally warm winter (and past summer,) makes it challenging for some trees such as the Aleppo pine to adapt to these challenges in the urban environment.  Below are a few tips to help your trees battle the warm and dry conditions our region is currently facing:

 

  • Water trees deeply: watering long intervals, allowing water to percolate to the depth of 2-3 feet is recommended. Allow the upper few inches to dry between cycles.
  • Use soaker hoses to water trees with canopies larger than 15 feet. Ideally, water should be applied close to the drip ring of the tree.
  • Do not depend on turfgrass sprinklers to water your trees, which typically only waters the upper 4-8” of soil. Supplemental water will be needed for non-native trees planted in turfgrass from May- September.
  • If you have forgone overseeding your turf, don’t forget to water the trees during the winter. Some trees, such as the Aleppo pine greatly benefit from winter rain, but when rain doesn’t come, irrigation is required.  Watering trees monthly in the cooler months is recommended, especially during drier periods.
  • Larger trees need a greater amount of water. Retrofit your irrigation system as trees mature. Drip emitters should be added and moved out towards drip lines as canopy sizes increase.
  • If your turfgrass has been or plans to be converted to d.g., establish supplemental irrigation well in advance, ensuring the established trees receive adequate irrigation.  A few drip emitters around the base of established trees generally is not sufficient. Ask your Landscape Contractor or Certified Arborist about water requirements for your trees.
  • Ensure mulch is covering the soil to help reduce evaporation of moisture from the soil; mulch can be decomposed granite or organic bark mulch.

 

For more updates on drought conditions, the US Drought Monitor updates data regularly. http://droughtmonitor.unl.edu/ . Also, ask your Landscape Contractor if your irrigation system is watering your mature trees efficiently and if upgrades are needed to improve growing conditions.  While chronic drought is impacting our urban trees, supplemental irrigation and proper irrigation management will be necessary to help keep trees healthy during the most stressful period of the year: the impending summer.

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