Preventing and Treating Iron Chlorosis in Trees and Shrubs …

Preventing and Treating Iron Chlorosis in Trees and Shrubs by Michael Kuhns, Extension Forestry Specialist, and Rich Koenig, Extension Soils Specialist

Note: See What is Iron Chlorosis and What Causes It? (click on link) for information on causes of iron chlorosis.

Diagnosis As noted above, go to What is Iron Chlorosis and What Causes It? for more information on what iron chlorosis is and its causes. Briefly, iron chlorosis is a yellowing of plant leaves caused by iron deficiency, usually in high pH soils (pH above 7.0). Other causes of yellowing need to be ruled out first, however. For example, leaf yellowing can be due to insect or disease problems (pathogenic diseases caused by fungi or other organisms), herbicide misuse, or a history of over watering. Some tree cultivars have even been developed to have yellow foliage on purpose -- an example is the 'Sunburst' honeylocust ('Gleditsia triacanthos' var. inermis 'Sunburst').

Pin oak with severe iron chlorosis.

The same pin oak 6 weeks later after injection with ferric ammonium citrate.

Soil application of ferrous sulfate and granular sulfur.

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Preventing and Treating Iron Chlorosis in Trees and Shrubs ...