Lemon tree leaves can turn yellow due to lack of nitrogen, overwatering, underwatering, pest attack, magnesium deficiency or iron deficiency. Each of these problems can be treated to save your tree and to make sure you still get a good crop of fruit.
This article will explore the top causes of yellow leaves on lemon trees and what you can do to fix each one.
1. Lack of nitrogen
Lack of nitrogen is the top cause of yellow leaves on lemon trees. Lemon trees need nitrogen for healthy leaf growth, where chlorophyll, the green pigment forms in the leaves. If the lemon tree lacks nitrogen then the leaves will become pale and yellow and can eventually die back.
Apply a dose of liquid nitrogen fertilizer to your lemon tree for a quick nitrogen boost. This can be watered on the root zone to feed the roots immediately. After 2 weeks apply a few handfuls of citrus fertilizer that contains nitrogen or pelleted chicken manure.
Water it in and this will give the plant the nitrogen it needs for the next 3 months. Feed lemon trees at the start of each season with pelleted chicken manure or a good quality citrus feed. This will help to replace the nitrogen lost out of the soil as the tree grows.
Overwatered lemon trees can often develop yellow leaves. Overwatering will compact the soil making it more difficult for the roots to take up the oxygen and nitrogen they need.
Extreme overwatering and soil compaction can cause the roots to develop fungal root rot. This can damage the ends of the roots that absorb the nutrients and water.
To see if your lemon tree is overwatered, check the soil with your finger. If it is damp or wet 2 inches down then the plant does not need more water.
Reduce your watering schedule and only water when the soil starts to dry 2 inches down. You can use a watering system with a timer to give your lemon tree a regular amount of water. In winter and fall the tree will only need water every 2-3 weeks.
In summer, the tree may need watering up to 2-3 times per week depending on your climate and the amount of rainfall you get.
Underwatered lemon trees can develop dry and yellowing leaves. Lemon trees can dry out quickly on hot summer days so make sure you water them in the morning if hot weather is predicted.
For trees that have already developed yellow leaves, deep water them around the root zone with a hose to make sure the whole area is damp. Cover the area with 2-3 inches of bark mulch and water again when the top layers of the soil have dried out.
4. Pest attack
Sap sucking insects like spider mite and aphids can cause yellowing on lemon tree leaves. These insects can attack throughout the year but are most likely to attach themselves to young lemon tree leaves.
Bronze orange bugs or stink bugs are also a common problem in spring. They will attach to new leaf growth, sucking the sap and causing the leaf to wilt and turn yellow.
Sap sucking insects are effectively treated with neem oil. This natural oil comes from the neem tree and can be sprayed all over the leaves and new growth to treat the pests.
Bronze orange bugs can be removed with a sharp spray of the hose and by squishing them with your foot once they reach the ground.
5. Magnesium deficiency
Magnesium deficiency can cause the veins to stay green when the rest of the leaf can turn yellow. Magnesium is a key nutrient that lemon trees need. They use up large amounts in the production of fruit so it needs to be replaced.
Feed lemon trees at the start of each season with a citrus fertilizer that contains magnesium. This is the easiest way to prevent a deficiency in magnesium.
If your tree already is showing signs, apply Epsom salts to your lemon tree. For more on this, check out my article on how to apply Epsom salts to lemon trees.
6. Iron deficiency
Lemon trees can turn completely yellow if the tree is deficient in iron. If the problem continues the whole tree will stop producing fruit and can start to die back.
Iron deficiency can be treated easily with liquid iron chelates. Dissolve it in water and pour it around the root zone of your plant. To prevent the problem in the future, feed them regularly with a fertilizer rich in iron. I like to use a good quality citrus fertilizer and apply this at the start of each season.
How to fix a lemon tree with yellow leaves
Here are the top 3 steps to follow if your lemon tree leaves turn yellow.
1. Check the soil moisture
Stick your finger 1-2 inches below the surface of the soil to check the moisture level. Water it regularly for the next 3 weeks every few days after if the soil is dry. If the soil is overly wet and you suspect overwatering, let the soil dry out and reduce your watering schedule.
2. Liquid feed with nitrogen fertilizer
Add dilute liquid fertilizer to the lemon tree then follow up with a few handfuls of pelleted chicken manure. This will give tree the nitrogen it needs to recover.
3. Trim off yellow and brown leaves
Once you have taken these steps for a few weeks and any frosts have passed, trim off any old and damaged leaves can be trimmed off with sharp secateurs.
I am an accredited practicing dietitian, experienced gardener and a dedicated cook. I love writing and sharing my experience so you can learn from my successes and mistakes.