indoor orange tree problems

Asked June 1, 2016, 4:37 PM EDT

I have a forty to fifty year old orange tree that is an in a 18 inch pot. Over the last it year has developed yellowing which starts on the outside of the leaf leaving lines of green in between.the yellowing. There is a lot of new growth. The newest growth remains green and then slowly turns yellow. I Have been told that it is chlorotic and should be fed iron every two months. The amount (suggested by the company) is four table spoons put around the edges. Ive done this and the plant is still yellowing. I have also tried Magnesium and the problem remains. It has lots of new growth even with this situation.
I would appreciate any information on what to feed it; how much and at what intervals. As I said it is in an 18inch diameter pot that is 19 inches high.

New York County New York fruit trees orange tree

3 Responses

What form of Iron are you using?
I would take soil pH test of the pot soil Using a pour through method. Water the tree thoroughly and wait for it to drain. Add about a cup of distilled water to the pot and collect the part that drips out, and measure the pH of the collected water. If the pH is high you will want to use an acid fertilizer to lower the pH to 7. You should also test the water you are using to water the tree, if it has a high pH it could raise the pH of the soil in the pot affecting the availability of Ca, Mg and Iron. I do not know what you are using to fertilize the tree. Does your fertilizer include Micro nutrients. I would do some testing before I just started adding any thing else.

I used an organic iron tone fertilizer by Espona It contains nitrogen 2.00 percent;phosphate 1.%,
potash3.0%, Calcium 1.5%, magnesium 0.7% ,sulphur 13.0% and Iron 5.0%
You suggested getting the PH .by adding water to run through the pot and then a cup of distilled water to run through it. The pot is huge. One cup of water wouldn't reach the bottom. Is there any other way I can get a reading for the PH.?
Thanks for any information you can supply.

Remove enough soil from the large pot to fill a 4 Inch pot. Try to take soil down at least 6 Inches in several different spots. Then do a pour through of the soil in the 4 inch pot. You can also do a salts test using the same using the same water you collected for the pH test. The choice of fertilizer sounds fine. If the tree is root bound it might also be time to move the tree to a larger pot.