My azalea leaves are turning yellow – what is the problem?
Azaleas are acid lovers. Certain minerals, including iron, are more available at lower pH values. Yellow leaves on azaleas can indicate an iron deficiency because (1) not enough iron is present in the soil for the azaleas to utilize, or, more commonly, (2) the pH is too high to release the iron that is present. Azalea fertilizer is usually a sufficient acidifier to keep the soil within the proper pH range for maximum nutrient availability. Supplemental applications of iron in the form of iron sulfate or iron chelate will supply iron when the azalea fertilizer is inadequate. It is nearly impossible to permanently adjust a naturally alkaline soil. Therefore, azaleas and other acid-loving plants should not be selected for that site. Also remember that mites, poor drainage, low nitrogen, and/or too much sun can also turn leaves yellow.
When the new growth of azaleas turns yellow, it usually indicates an iron deficiency. Azaleas prefer soils which have an acid pH because certain nutrients, including iron, are more available at lower pH values. Yellow leaves on azaleas can indicate an iron deficiency because (1) not enough iron is present in the soil for the azaleas to utilize, or (2) the pH is not low enough to release the iron that is present. Azalea “special” fertilizer contains soil acidifiers which temporarily lower (acidify) the soil pH. Applications of iron sulfate or iron chelate will also correct iron deficiencies. Coastal soils are naturally alkaline and it is nearly impossible to permanently adjust a naturally alkaline soil. Therefore, azaleas and other acid loving plants should not be selected for that site. Yellowing leaves on azaleas can also be an indication of a root rot fungus due to poor soil drainage; planting too deep (see question 7 below); or poor establishment (see question 3 below).
