Iron Deficiency in Trees

I’m Told My Trees Have an Iron Deficiency.  What Does That Mean and Can It Be Managed?

by Sarah Sours, I.S.A. Certified Arborist

Iron Deficiency in trees is a common problem in North Central Texas.  It is most frequently seen in a neighborhood with Red Oak, Sweetgum, or Silver Maple that never reaches a dark green color as spring leaves develop into summer foliage.  A closer look may reveal leaf tissue that is yellow, while the leaf veins remain green.  Extreme Iron Deficiency displays yellow leaves with brown edges, or leafless twigs.

Description of Iron Deficiency in Trees

While a soil test may indicate sufficient iron for good plant growth, our alkaline soils (high pH) lock up this essential mineral, preventing its uptake into the tree’s vascular system.  When iron is not available in the leaves to produce green chlorophyll, the tree’s ability to produce energy is reduced.  This can stress the tree, making it susceptible to other problems or causing it to grow more slowly, or decline.  In some cases, the tree does not show symptoms until it has been planted in the yard for more than 5-10 years.  This is because the root system is growing further out into the soils and the needs of the tree are greater.  The trees that most often show Iron Deficiency in North Central Texas include Red Oak, Pin Oak, Sweetgum, Pine, River Birch, Crabapple, Silver Maple, and Bald Cypress.

Treatment of Iron Deficiency in Trees

When Iron Deficiency symptoms are mild, they may be addressed by amending the soil.  The pH of a soil can be lowered by applying sulfur.  By doing so, the iron that currently exists in the soil is released and the tree can pull it from the soil.  Additionally, extra iron can be added to the soil if necessary.  This can be done several times during the year, but it is most effective in the spring and fall.

High Volume Injection is another method of providing supplemental iron.  A material containing chelated iron can be  injected directly into the tree’s root flare.  Arborilogical Services has been treating trees with Iron Deficiency with the chelated iron product, Verdur®, for a number of years.  It is consistently meeting our expectations.  Verdur should be applied once every three years while the tree is in its winter dormancy.  Verdur can be applied exclusively, or in combination with soil amendments.

In some situations, it may be better to remove the tree and replace it with a species that is better adapted to the existing soil’s pH.  Your Certified Arborist can provide you with a list of recommended trees for your area.  The decision to replace a tree should be based on the homeowner’s opinion of how important the tree is to them, the cost of treatment for the tree’s life, and the tree’s overall health.

Expectations

Amending the soil and adding iron can be successful in addressing  mild symptoms of Iron Deficiency, but it is frequently short-term and only masks the symptoms.  The soil will likely need amending on a regular basis.

High Volume Injections have proven to be more successful than soil amendments.  The procedure must be repeated once every three years.  Again, the treatment only masks the symptoms, but the results are favorable in even the most extreme cases.

If the tree is new to your landscape and you don’t have years invested in it, replacement is recommended.  If the tree is older and important to the landscape and home, treatment should be considered.  Cost of treatment is determined by the tree’s size.  Your Certified Arborist can assist you in determining what might be best for you and your tree.