Iron aids in production of the green plant pigment, chlorophyll, as well as in plant enzyme functions. If the soil is too alkaline, with a pH over 7, iron may not be available to the plant. Soggy, poorly aerated soils also inhibit iron release. In iron-deficient soil, the early leaves of a plant get whatever is available. Once the iron is absorbed by the plant tissue, it cannot be reused by new leaves, which then suffer the most severe damage.
Leaves lose green color, starting at the outer edge and progressing inward, a condition called chlorosis. Leaf veins usually remain green. In plants with severe iron deficiency, these leaves are very small and may turn completely white or bright yellow, while older leaves remain green.
For prevention test soil pH before planting in any area or correct the soil pH to the recommended levels before putting in plants. Also add organic matter before planting and check garden's drainage and use mulches to increase soil water retention. Apply a fertilizer containing chelated iron according to the directions on the label.