If some of the woody ornamental plants in your landscape look a little pale, the off-color could be the result of iron deficiency. Azaleas, Japanese hollies, and hydrangeas are examples of woody ornamentals which are especially susceptible to this condition.
Iron deficiency causes yellowing of the newest foliage in a definite pattern.
The leaf veins usually remain green while the areas between the veins becomes yellow-green to yellow in color. This problem should not be confused with nitrogen deficiency, which usually shows up on the lower foliage first and causes an even light-green color. Iron deficiency may be caused by several things which result in poor uptake of iron from the soil. Ph may be too high. When excessive lime is applied or when there is a great deal of construction mortar in the soil, chlorosis often occurs.