There are many potential causes of chlorosis.
What is chlorosis?
This condition is resulting from a lack of chlorophyll, resulting in light green or yellow leaves.
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Nutritional deficiency is one of many causes of chlorosis.
Overwatering
When yourcitrus' leaves yellow and drop prematurely, overwatering may be the underlying cause.
Identifying and quickly correcting this issue helps avoidroot rotand plant loss.
In addition to rot, overwatering also dilutes and washes away nutrients.
Develop a good watering schedule, and water deeply but infrequently.
Allow the top 2 to 3 inches of soil to dry out in between waterings.
Use a citrus potting mix and a pot with plenty of drainage holes.
Soggy potting medium can be discarded and the tree repotted in fresh, dry material.
For in-ground trees avoid low spots where water pools andamend clay soilswith aged compost before planting.
If your in-ground tree is too wet, allow it to dry out completely, then water less often.
Underwatering
Foliage that lacks moisture turns yellow, then brown and dry.
If the soil is dry, give the plant a deep, thorough watering, letting excess drain.
Dry soil can drain very quickly, so wait several minutes and repeat.
Check every day for moisture and continue to drench and drain until the soil holds moisture.
Watering Tip
Both overwatering and underwatering can cause leaves to yellow.
Nutrient deficiencies cause yellow spots and loss of color on foliage.
Lack of Iron
New leaves that emerge yellow or with yellow veins indicate iron deficiency.
The problem spreads to older leaves and can turn them almost white when severe.
The cause is lack of iron available in the soil, but it also can be due to overwatering.
Reduce frequency of watering if needed.
Discoloration occurs between green veins, and necrotic spots appear along the center blade of the leaf.
New shoots may be stunted, and problems can advance to older foliage.
Spray leaves with afoliar kelpsolution, or add zinc oxide directly to soil.
Leaves often appear dry but, unlike with zinc deficiency, not stunted.
This condition often occurs in winter but improves on its own when spring growth begins.
If the problem persists, treat soil with a granular manganesefertilizeror dilute it in water and spray foliage.
It needs close to eight hours of direct sunlight daily.
Overwinter your potted lemon tree indoors directly in a south- or southwest-facing window to give it the best light.
If you aren’t able to relocate your tree, try removing or reducing other foliage shading the tree.
Cold
Lemon trees thrive in tropical and subtropical environments.
Newly planted and potted trees are more vulnerable to low temperatures.
Move your potted lemon tree indoors when night time temperatures remain steadily below 40F.
Cover susceptible outdoor trees with frost cloth when extended cold temperatures are forecast.
Water thoroughly beforehand to protect roots against frost damage.
This seldom results in the death of a plant, but infestations can cause significant damage.
Check the stems and undersides of leaves for pests.
An overwatered lemon trees may have droopy, yellow leaves.
It may also emit a foul smell, if rotting.
This may happen more or less often depending on the time of year and other factors.
However, it would be more efficient to treat the soil with a balanced fertilizer.
How do I feed my citrus tree?.
University of Arizona Cooperative Extension.
