Lemon Tree Leaves Turning Yellow – Reasons Why?

Lemon Tree or Citrus limon, just like its fruits, has a refreshing and cooling effect when grown as house plants or in gardens and parks. 

These small, evergreen trees are widely acclaimed for their hardiness (USDA hardiness zone 9 and above), tolerance towards different soil types, ability to grow in sunlight, lush green foliage, and pulpy, sweet fruit.

Common varieties of lemon tree include Eureka, Lisbon, and Meyer. 

More on –> Meyers Lemon Tree Care

Leaves on a Lemon Tree turning yellow

Leaves of a healthy tree have a reddish appearance initially and turn dark and light green as the tree matures. 

However, if the leaves lose their color and turn yellow, it is a cause of concern.

Yellow Leaves on Lemon Trees: Is It Normal?

Yellow leaves on a lemon tree are an indication of several underlying problems. 

Hence, the overall inspection of the plant is important to diagnose the cause of this discoloration. 

To identify the cause, the following factors must be considered:

  • The location of the yellow leaves in the foliage
  • The age of the yellow leaves
  • The degree of discoloration
  • The condition of the soil
  • The frequency of watering the plant

Possible Causes of Lemon Tree Leaves Turning Yellow

Lemon tree leaves turn yellow when watered very frequently. They can experience nutritional deficiencies, toxicity, and diseases. 

Pests and extreme weather conditions also cause yellowing leaves.

Overwatering

Overwatering Citrus trees can lead to root rot. 

Lemon trees have shallow roots and are at risk of being overwatered by sprinklers if planted in lawns. 

Rotten roots appear blackish-brown and slimy and fail to absorb the necessary nutrients from the soil and the yellow leaves are a manifestation of this condition.

Nutritional deficiencies

Yellow foliage on a lemon tree indicates the plant’s nutritional needs are unfulfilled. 

Deficiency of nitrogen, a mobile nutrient in plants, is the most common. 

The plant will direct nitrogen from older leaves to the newer ones if there is a shortage. 

Consequently, the leaves of the tree will turn various shades of green and yellow.

Magnesium, Iron and Zinc, the immobile nutrients, cause chlorosis in fresh leaves. 

Due to lack of magnesium, the leaves get a yellowish blotchy base, whereas iron and zinc deficiency turns the leaf pale while the veins remain dark.

Nutritional deficiency causes yellow foliage on a lemon tree. 

Symptoms vary according to which nutrient is lacking. 

Nitrogen deficiency causes light green to yellow leaves all over the tree; magnesium deficiency appears as a yellowish-green blotch at the leaf base spreading outward, and yellow leaves with green veins are caused by zinc or iron deficiency.

Learn about –> What is Chelated Iron Fertilizer?

Diseases

If a lemon tree starts turning yellow, it’s often a symptom of certain diseases. 

The tree may be suffering from Phytophthora root rot due to poor drainage of the soil. 

If the chlorosis is limited to one part of the tree or there is no symmetrical discoloration on the leaves, this might be a sign of citrus greening – a disease transmitted by psyllids or aphids. 

Citrus greening is confirmed by looking for additional symptoms like stunted growth, falling leaves, lopsided fruit, and twig dieback.

Alkaline Soils

Soils with pH levels above 7 lack the nutrients and contain minerals like sodium and chlorine which are toxic for the lemon tree. 

Apart from mottled or yellow leaves, toxicity will cause stunted growth and early leaf fall.

Extreme weathers

Extreme hot and cold weather conditions scorch or bleach the leaves. 

Trees grown in regions with temperatures above their hardiness can have yellow foliage.

Pests

Pests like spider mites and whiteflies damage the leaves by feeding on the tree sap. 

Insects feast on the fruits as well and turn the leaves yellow.

Fix The Foliage: How To Get Rid Of The Yellow Leaves?

It is necessary to ensure deep but infrequent watering and proper drainage for the lemon tree. 

Water the tree once a week if young and once a month if fully mature. 

Redirect sprinklers away from the tree if it stands in the garden. 

Use a drip line for soaking the tree.

In the case of root rot, repot the plant in a container draining quickly and containing dry soil. 

Add fertilizer later to accelerate new growth. 

Use acidic planting mix to lower the pH of the soil.

Fulfill the nutritional needs of this heavy feeder plant by nitrogen-rich fertilizer thrice annually. 

Foliar sprays filled with chelated zinc or iron and foliar nitrogen like urea are also used to overcome deficiencies and improve tree health.

If the tree shows signs of infestation, direct the hose with a full stream on the insects or pests. 

Insecticidal soaps are also beneficial for pest control in lemon trees.