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Chlorosis is the yellowing of leaves due to a lack of chlorophyll. More specifically, iron chlorosis is the lack of chlorophyll caused by an iron deficiency. Leaves that are yellow due to the lack of chlorophyll are not providing the energy a normal healthy leaf would. Reduced energy production results in tree stress, which makes the tree more susceptible to abiotic injury, as well as insects and disease.
Symptoms
- Yellow leaves with green veins (figs. 1 & 2)
Fig 2. Iron chlorosis in a maple tree. In the top of the picture there are green older leaves while in the center of the picture are yellow leaves with green veins. - Brown spots can develop between veins
- New leaves yellow but older leaves remain green (fig.3)
- Leaves may be smaller than normal
- If left untreated, can result in branch or plant death (fig.4)
Iron chlorosis can be confused with:
- Zinc or manganese deficiencies, yellowing starts on old leaves rather than new
- Nitrogen deficiency, uniform yellowing of leaves
- Soil sterilizing herbicides, area around vein remains green
Fig 4. Pin oak with iron chlorosis and severe dieback. It is likely that other factors along with iron chlorosis are causing dieback in this tree.
Fig 3. A chloritic maple tree. New growth on the outside of the tree is yellow while older growth near the trunk is green.
Causes
Iron chlorosis is not fully understood and many factors can cause or influence the deficiency.
- Alkaline soils
- If there is too much calcium in the soil or the pH is too high, iron may get tied up in forms that are unavailable to plants.
Fig 5. Girdling roots cause stress, including chlorosis, and eventually tree death if not corrected. These roots were exposed with an air spade.
- If there is too much calcium in the soil or the pH is too high, iron may get tied up in forms that are unavailable to plants.
- Over watering
- Watering too much, especially in the spring, can leach iron from the root zone.
- Soil compaction
- Compaction limits pore space in the root zone causing oxygen depletion, thereby limiting root growth.
- Girdling roots (fig. 5)
- Roots that wrap around the trunk strangling the tree causing nutrient deficiencies, if left uncorrected, will lead to death.
- Other problems
- Plant competition, winter injury, excessive organic matter or salt, extreme soil temperatures, acid loving plants, and excessive levels of nutrients can all contribute to iron chlorosis.
Treatments
There are several ways Wellnitz Tree Care can treat iron chlorosis. There is usually no long term solution for iron chlorosis, however problems like girdling roots and soil compaction can be corrected by air spading. Wellnitz Tree Care can do soil amendments if soil pH is too high, however if high levels of calcium carbonate are present, this will be ineffective. Soil amendments will generally have to be done every several years to keep the soil balanced. We also offer iron injections into the trunk of the tree (fig 6) which are good for up to three years.
If your tree looks yellow and you suspect iron chlorosis or some other problem feel free to contact us. We would love to help make your trees healthy and beautiful!
For more information on Iron Chlorosis check out these helpful links:
K-State Extension
Colorado State University Extension
Missouri Botanical Garden
