Plum Leaves Yellow After Iron Application. Why?

Q. I have a Burgundy plum tree that is 3 years old. The older leaves are starting to get some yellow in them. I applied Arizona's Best Kerex Super Iron Chelate for high alkaline soils in mid-March when I first noticed the problem. The new leaves do not show any yellow in them so I don't think it's an iron issue.

A. It is still an iron issue. You said the NEW leaves do not show any yellow. That means your KeRex application in March worked. Iron does not move around inside the tree once the plant takes it up, it only goes into the new growth after the application was made. Older growth stays yellow.

Plum tree new growth darker green color while older growth still yellow.
This is due to a late soil application of an iron chelate.

The only way to solve yellowing on the older leaves is with iron applications applied to the foliage. This is why SOIL applications of iron are important to make in January before new growth appears.

It is not too hot to late to make foliar applications of iron if done during the cool morning hours. Normally it will take four or five sprays a couple of days apart to get it to completely green up.

Older leaves of plum showing green veins and yellow leaf
typical of an iron shortage.

Any iron product that has been labeled for foliar applications to fruit trees should work for you. However, I would strongly suggest that any water mixed with all foliar applied product should be distilled water so that the pH is close to neutral (7) or that you adjust the tap water close to neutral as well.

You can use vinegar. About 1 to 2 tablespoons of vinegar in a gallon of water should be enough but you should check it with lit

mus paper. Litmus paper used for adjusting the pH of pool water is fine.

The second thing that you need to apply with any fertilizers applied to the leaves of plants (foliar applied) is a wetting agent. Some people may use liquid detergents with good success. I worry a little bit about all of the other personal care products in liquid detergents.

I prefer to use a wetting agent that is manufactured for that purpose. There are several available. I consult for Viragrow and I know their product lines very well. I happen to like a product they carry called EZ Wet for doing this. I think it runs for about $14 per quart.

Iron product used for spraying fruit tree leaves
to correct yellowing

You usually add one or 2 teaspoons or a tablespoon in each gallon of finished spray solution. Some people have claimed success with products like Dr. Bonners and Castile soap. I have never use these products so I don't know.

Here is the sequence you would use:

• Use either distilled water or adjust the water you are using to a pH of seven using vinegar. Use only as much as you think you will need with one application.
• Add an iron product to this pH adjusted water that is labeled as a foliar applied iron fertilizer for plants. Follow the label rate. Adjust the pH before you add the iron.
• Add a wetting agent like EZ Wet to the total amount of finished spray. Do not add it first and then add water. Add only at the very end.
• Mix the water, iron fertilizer, vinegar and wetting agent thoroughly.
• Apply it early in the day or late in the day when temperatures are cool. Apply enough of the mixture until this mixture begins to run off the surface of the leaves. More than this is just wasteful.
• Use all of the product that you have mixed. Do not save it for a later application. If you have more than you need, apply it to other plants or the soil surrounding the tree.
• Rinse your sprayer thoroughly.

Apply the solution to the leaves every couple of days until they turned dark green. More than one application will be needed.





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