Why Lemon Tree Leaves Turn Yellow In NZ And How To Fix It

Causes and Solutions for Lemon Tree Yellow Leaves

Growing lemon trees can be a rewarding endeavour, but what happens when the vibrant green leaves start turning yellow? If you've noticed your lemon tree leaves going yellow, you're not alone. Many gardeners face this issue, and fortunately, there are clear causes and solutions. In this guide, we’ll explore the reasons behind this phenomenon and discuss how you can restore your lemon tree to its lush, green glory.

Understanding Why Lemon Tree Leaves Turn Yellow

Lemon tree leaves turning yellow can be a sign of distress. This discoloration often indicates that the tree is experiencing some form of stress or nutrient deficiency.

Nutrient Deficiencies

• Magnesium Deficiency: This is the most common reason for the leaves on a lemon tree to turn yellow is a magnesium deficiency. During cold weather or with heavy crop loads, the roots cannot take up enough magnesium to supply the developing fruit. The plant then robs magnesium from the leaves to keep the fruit growing. The solution is to apply fortnightly applications of a foliar fertiliser along with citrus fertiliser and the yellowing will go away after 8-12 weeks.
• Nitrogen Deficiency: Lemon trees need nitrogen to maintain their green colour. A lack of nitrogen often results in older leaves turning yellow first. Again, foliar fertiliser along with citrus fertiliser and the yellowing will go away after 8-12 weeks.
• Iron Deficiency: Yellowing between the veins of younger leaves can indicate an iron deficiency. This condition, known as chlorosis, is common in alkaline soils. Use [acid fertiliser] in conjunction with a foliar fertiliser to address this issue.

Watering Issues

Watering problems can also cause lemon tree leaves to yellow. Both overwatering and underwatering can stress the tree.

• Overwatering: Too much water can drown the roots, leading to yellow leaves. Ensure your lemon tree has well-draining soil to prevent waterlogging.
• Underwatering: On the flip side, not enough water can cause the tree to dry out, resulting in yellow leaves. Regular, deep watering is essential, especially during dry spells.

Pests and Diseases

Pests and diseases can also be culprits when it comes to yellowing leaves on lemon trees.

• Aphids and Spider Mites: These pests suck the sap from the leaves, causing them to yellow and curl.
• Citrus Canker: This disease, caused by bacteria, leads to yellow lesions and can severely affect leaf health.

Environmental Stress

Environmental factors such as temperature and sunlight can also impact leaf color.

• Temperature Fluctuations: Extreme temperatures, whether hot or cold, can cause stress and lead to yellow leaves.
• Lack of Sunlight: Lemon trees thrive in full sun. Insufficient sunlight can cause leaves to yellow and drop.

Solutions for Yellow Leaves on Lemon Trees

Now that we've identified the potential causes, let’s discuss practical solutions to bring your lemon tree back to health.

Correcting Nutrient Deficiencies

• Fertilise Properly: Use citrus fertilizer in spring and again in autumn to provide essential nutrients. Follow package instructions carefully to avoid over-doing the fertiliser.
• Adjust Soil pH: If iron deficiency is suspected, check the soil pH and adjust it if necessary using [acid fertilser].

Watering Wisely

• Check Drainage: Ensure your pot or planting area has proper drainage to prevent waterlogging.
• Establish a Watering Routine: Water deeply but less frequently to encourage root growth. Use mulch to retain moisture in the soil.

Managing Pests and Diseases

• Regular Inspections: Check your lemon tree regularly for signs of pests and use an appropriate insecticide.
• Disease Prevention: Prune any infected leaves and dispose of them properly. Try to avoid overhead watering as this will help to reduce disease spread.

Mitigating Environmental Stress

• Protect from Extremes: Provide shade or move potted lemon trees indoors during extreme weather conditions.
• Ensure Adequate Sunlight: If your lemon tree is indoors, place it near a north-facing window to maximise sunlight exposure.

Preventative Measures

Taking steps to prevent yellow leaves can save you time and ensure your lemon tree remains healthy.

• Consistent Care: Establish a regular care routine that includes watering, feeding, and pruning.
• Monitor Conditions: Keep an eye on weather forecasts and adjust your care practices accordingly.
• Soil Testing: Conduct soil tests periodically to ensure nutrient levels and pH are optimal.

When to Seek Professional Help

If your lemon tree leaves continue to yellow despite your best efforts, it may be time to consult a professional. The Plant Company is always here to give sound advice.