Ash Tree Leaves Turning Yellow in Mesa, Arizona

Are your ash tree leaves turning yellow? Are leaves falling early, or is the canopy becoming thin? Yellow leaves do not automatically mean your tree is dying, but they deserve attention when they appear during the growing season or come with dead branches.

Warner of Warner's Tree Surgery has more than 50 years of experience treating sick trees in the Phoenix area. He evaluates the symptoms, watering conditions, and overall condition of the tree before recommending what to do next.

Watch: Why Are My Ash Tree Leaves Turning Yellow?

What Causes Yellow Leaves on an Ash Tree?

Several problems can produce similar symptoms. The timing of the yellowing, the leaves affected, and the condition of the branches help narrow down the cause.

  • Normal seasonal changes: Deciduous ash trees naturally turn yellow and lose leaves as they enter dormancy. Timing varies with the type of ash and weather.
  • Watering problems: Too little water, uneven watering, or soil that stays too wet can stress the root system.
  • Nutrient availability: Yellow tissue between green veins, especially on newer leaves, can suggest an iron availability problem. This pattern alone does not confirm the diagnosis.
  • Root and soil problems: Compacted soil, poor drainage, or damaged roots can interfere with water and nutrient uptake.
  • Insects or disease: Yellowing accompanied by thinning foliage, small leaves, or branch dieback needs a closer inspection.

Should I Give My Ash Tree More Water?

Check the soil and irrigation system before increasing watering. Yellow leaves can occur when roots are too dry or too wet. A watering schedule should account for the tree's size, soil, drainage, season, and recent weather.

Water needs to reach a broad area of the root zone. Watering only beside the trunk may leave much of the absorbing root system dry. Check for clogged emitters, leaks, and uneven coverage.

Does My Ash Tree Need Iron or Fertilizer?

Not every yellow ash tree needs fertilizer. Arizona's alkaline soils can make iron less available to roots, but root stress and other problems can also cause yellowing. An inspection and, when appropriate, soil or tissue testing can help determine whether a nutrient treatment is needed.

Avoid applying fertilizer, iron, or pesticides simply because the leaves are yellow. Treatment should address the cause.

When Should I Have My Ash Tree Inspected?

  • Yellowing appears during active growth rather than seasonal leaf drop.
  • One side or one large section changes color.
  • Leaves are unusually small or the canopy is becoming thin.
  • Twigs or branches are dying.
  • The problem returns or becomes worse.

Take pictures of the entire tree and close-ups of affected leaves. Note when the symptoms started and any recent watering changes, digging, landscaping, or construction near the roots.

Call Warner About Your Yellowing Ash Tree

For help with an ash tree in Mesa or nearby East Valley communities, including Gilbert, Chandler, Tempe, and Scottsdale, call Warner's Tree Surgery at 480-969-8808.

Warner can evaluate the tree and explain appropriate next steps. Recovery depends on the cause and extent of the problem.

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