5 Reasons Your Olive Tree Leaves Are Turning Yellow

Olive trees are subtropical evergreens and native to the Mediterranean. Due to their popularity and ability to produce an abundant annual crop, they are now grown across the globe.

Although they are fairly hardy and low maintenance, yellow leaves are a common issue that many people experience. 

Why Do Olive Tree Leaves Turn Yellow?

Healthy olive leaves are dark green. However, if the leaves have turned yellow, this means chlorosis has occurred. Chlorosis is the scientific term that describes the yellowing of leaves.

Healthy plants and leaves are green in color due to a special pigment called chlorophyll. This pigment absorbs sunlight which the plant uses to grow. 

When photosynthetic plants lack chlorophyll, their leaves turn yellow. A number of factors may trigger chlorosis including soil pH, nutrient availability, water quantity, temperature, and pest infestations. 

Figuring out why your olive tree is experiencing chlorosis can be tricky. This article lists additional symptoms alongside yellowing, to help you pinpoint the exact cause. 

1. Leaves Turning Yellow and Drooping

Limp and droopy leaves that are yellow in color are most likely a sign of overwatering or root rot.

If an olive tree is overwatered, the soil is likely to become waterlogged, especially if the soil is poor draining. Waterlogged soil deprives the olive tree roots of oxygen, inhibiting them from absorbing essential minerals and nutrients from the soil, causing the leaves to yellow.

Olive trees that remain waterlogged for substantial periods of time can develop root rot. Excess moisture in the soil provides the perfect conditions for fungal infections to attack the roots. Infected roots will become rotten and die, leading to the yellowing of leaves which will eventually drop off.

2. Leaves Yellowing with Dry Brown Edges

Being native to the Mediterranean, olive trees are used to hot and arid conditions. However, they still require water and without sufficient amounts, yellow leaves with dry brown edges will occur. 

Water acts as a medium through which nutrients are transported throughout the plant. Too little water will hinder the number of nutrients being sent to the leaves, causing them to turn yellow. 

Underwatered olive tree with yellow leaves and brown edges - olive tree leaves are turning yellow
Underwatered olive tree with yellow leaves and brown edges

Prolonged periods of drought will see the peripheries of the leaves become brown and brittle. These brown patches of dead cells cannot recover, and the leaf will soon drop off. Hot and arid conditions will further exasperate drought stress.

3. Leaves Turning Yellow and Falling Off

If your olive tree has leaves that are yellow all over (or very pale green) and constantly shedding, then lack of sunlight is the most likely culprit. 

Sunlight is essential for photosynthesis but if your olive tree is not receiving enough sun, it cannot photosynthesize which will result in the yellowing of leaves. 

4. Leave Yellow At the Edges

A nutrient deficiency is reflected in yellow leaves with curling edges. This can be caused by a lack of nutrient availability or soil composition. Depending on what nutrient your olive tree is lacking, leaves will vary slightly in their symptoms. 

If your olive tree has green upper leaves but yellow, curling older leaves then it is likely deficient in nitrogen. Older leaves curl as they lack the structural proteins which are synthesized from nitrogen. 

nutrient deficiencies
Yellowing at the edges or showing deep green veins is typical of nutrient deficiency

A magnesium deficiency affects mainly lower leaves. They begin to turn yellow from the outside in, but their veins will remain green. This is called interveinal chlorosis.  Magnesium is essential for the production of chlorophyll, hence a deficiency in this nutrient will cause the leaves to become yellow. 

Olive tree leaves suffering from a potassium deficiency will curl downward at the tips. Yellow edges and spots will also be present. Potassium is important for fruiting, so a lack of olives growing on your tree is another indication of a potassium deficiency.  

5. Leaves are Yellow with Brown Spots

If your olive tree has yellow leaves with black or dark brown spots, it’s a symptom of a disease or pest infestation. Peacock spot is a common fungal disease that affects olive trees, especially during the growing season. The fungus causes round lesions on the leaf which develop into dark spots. 

Peacock spots on olive leaves
Peacock spots on olive leaves

Pests including scale, mealybugs, aphids, spider mites, and whiteflies leave yellow and brown patches on the leaves from where they have sucked out the sap. If left untreated, pests may spread to an infestation and aid the spread of diseases. 

Avoiding Yellow Leaves on Olive Trees

After diagnosing the cause of chlorosis on your olive tree, the good news is many cases can be easily cured. Below I have compiled a list of steps you can take to reverse the yellowing of your olive tree leaves and help prevent future cases. 

Overwatering or Underwatering

To avoid overwatering, it’s best to let the top two inches of soil thoroughly dry out before watering your olive trees. The soil should be moist but not saturated to prevent root rot. 

Established, outside trees seldom need watering, but young, indoor trees require more frequent watering. Extra irrigation may be required during particularly hot and dry months. 

Make sure the tree has sufficient drainage, such as mixing grit into the soil and using pots that have drainage holes. Waterlogged soil is one of the main causes of nutritional deficiencies in olive trees.

Lack of Sunlight

Olive trees thrive in direct sunlight, so should be positioned where they will receive at least 6 hours of sunlight a day, but ideally between 8 and 12. 

Sufficient sunlight aids photosynthesis and helps the soil dry out to prevent waterlogging. Sunlight also dries out the leaves which inhibits the development of mildew and fungus. 

Nutrient Deficiency

Olive trees will grow happily in acidic, neutral, or alkaline soil that ranges between 6.5 and 8.5. Hence nutrient absorption is quite tolerant to soil pH.

Conducting a soil test is the best way to identify a nutrient deficiency. Once identified, you should feed your tree a fertilizer that is rich in the nutrient it’s deficient in to reverse the symptoms.

Feeding fertilizer to your olive trees once or twice a year during their growth phase will help prevent nutritional deficiencies. Frugal plants like olive trees are sensitive to overfertilizing and always follow the manufacturer’s recommendations when it comes to application rates.

Diseases and Pests

To treat an olive tree suffering from peacock spots you should first prune any infected leaves. Thoroughly spray your tree with a copper-based fungicide to kill fungus. You should spray your tree every year to prevent future outbreaks. 

Most pests can be hosed off with a strong jet of water. It’s also a good idea to spray your plant with an insecticide to kill and prevent infestations.

For more olive tree-related articles, here’s a link to Olive Tree Growth Stages that you find interesting.

FAQ Olive Tree Leaves Are Turning Yellow

Does chlorosis affect olive growth?

Olive trees suffering from chlorosis will often experience a lower yield and fruit that is reduced in size and quality. The olives that do grow will still be edible. 

How long do olive trees take to mature?

It can take decades for an olive tree to grow to its full size, which can be up to 30 feet in height. 

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.