Iron Chlorosis in the Low Desert

PLANTS MOST SUSCEPTIBLE: Pear, Eucalyptus, Pyracantha, Roses, Peach, Nandina, Citrus, etc.

SYMPTOMS:

Chlorosis occurs at all times of the year but is most common and severe in the late summer when high temperatures and dry air result in the need for heavy irrigation and in winter due to low soil temperatures, and root inactivity.
• Mild Chlorosis: New leaves are pale green or yellowish green between the veins of normal green
• Moderate Chlorosis: New leaves are very yellow between the green veins
• Severe Chlorosis: New leaves are pale yellow to ivory color; veins may or may not be green. Brown spots on leaves or whole leaf dry. Often leaves fall off.
  

Iron deficiency symptoms are similar in appearance to the symptoms of deficiencies of Nitrogen, Manganese or Zinc. However, Iron deficiencies appear on new leaves where Nitrogen appear on older leaves. The interveinal chlorosis caused by lack of manganese has a "Christmas tree" pattern, with the green not restricted to the veins as in Iron deficiency. Zinc deficiencies look like iron deficiencies but the leaves are much smaller than normal.

CAUSES:

There is almost always iron in the soil, but it may be in insoluble forms that are unavailable to the plant.
• Not allowing the soil to dry out between watering which results in a lack of available Iron (not bound up in the soil)

  Iron Chlorosis can be induced with wet soils keeping the oxygen levels low. Iron absorption by roots requires an active oxygen transfer and the less oxygen the less iron can be absorbed. Also, the wet conditions place the iron in a reduced (ionically) form that is less available for plants.

• High pH which results in the Iron being tied up in the soil and unavailable to the plants

• Infrequent, deep watering will prevent the problem
• Select native plants adapted to our soil conditions
• Reduce irrigation to the amount necessary to keep the plant in good condition. This is often sufficient to correct the problem.
• Apply available iron to the soil (Ferrous Sulfate or Iron Chelates)
• Apply available iron directly on leaves
• For annual planting beds incorporate organic matter to lower the pH
• It is not practical to try to lower the pH of the soil in which long lived plants are growing