Iron (Fe) is necessary for the production of chlorophyll in plant cells. So, it would seem reasonable that a deficiency of Fe would result in a loss of green coloration in the leaf. This yellowing of the foliage is called chlorosis and it takes on a characteristic form in Fe deficiency. In such situations, the main part of the leaf is yellow but the veins remain a dark green. The newer leaves on the plant will be affected most.

Iron deficiency in landscape plants may be present for one or both of two reasons.
  1. Lack of Iron - In some cases, there is just a low level of Fe in the soil and this will cause the deficiency symptoms. In these cases, an application of an iron compound called iron chelate will reverse the symptoms.
     

  2. Alkaline Soil - Sometimes a plant is showing an iron deficiency but the soil test says that there is plenty of Fe in the root zone. This is a situation involving the availability of the nutrient. Iron is one of those elements that can only be absorbed into the root when it is in an acid solution. If the pH is too high i.e. alkaline, the root cannot take in the iron even though it is in the soil.

    This is a common problem when growing so-called acid loving plants such as Rhododendrons, pin oak, boxwood, heaths and heathers, blueberries and members of the Ericaceae Family of plants.

    The treatment for this cause of the deficiency is to lower the pH of the soil in the root zone to about 5.0. This is not a simple process, especially on established trees and shrubs. Various sulfur products may be applied into the root zone of the plants but these may move very slowly down into the soil and you cannot work it in since that will destroy roots. If possible, the best approach is to either only plant these plants in acid soils or lower the pH prior to planting them.

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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