Yellow leaves - Knowledgebase Question

Corpus Christi, Te
Question by richard_c287
July 1, 2010
I have this lemon tree and the leaves are color yellow. What should I do to make the leaves go green again?


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Answer from NGA
July 1, 2010

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Yellow leaves can be caused by many things including lack of nitrogen, insufficient light, water-logged soil (plant roots need oxygen to thrive), dry soil, or iron deficiency. If the older bottom leaves are yellow, but new growth is green, it's usually a lack of nitrogen. If new leaves are yellow, with green veins, it's usually a lack of iron. (Lack of nitrogen is a more common problem than lack of iron.) Soil should be kept moderately moist (but not wet). Finally, transplant shock can contribute to yellowing. If new growth shows up as green, that might be the problem.

Citrus should be fertilized with a nitrogen fertilizer product 3 times per year in Jan/Feb; Apr/May; and Aug-Sept. Each feeding should contain 1/3 of the tree?s total annual nitrogen requirements. Requirements vary according to the age and size of the tree. According to the University of Arizona Cooperative Extension, a newly planted citrus tree takes 0.12 pounds of actual nitrogen per year, so each feeding would be 1/3 of that. A tree 1-2 years in the ground, takes 0.25 pounds of actual nitrogen. Keep adding 0.25 pounds every year or so, until the tree is 6 or more years old. At that point, the mature tree takes 1.5 pounds of actual nitrogen annually. The amount to apply depends on the percentage of nitrogen in the product. If you don't want to figure that out, you can buy a fertilizer formulated for citrus, but it's more expensive than just plain nitrogen (such as ammonium sulfate). Spread fertilizer at the outer edges of the tree canopy, or dripline, where feeder roots can absorb it. Water deeply immediately after applying fertilizer.

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