Why Olive Trees Get Brown Leaves (& How to Fix It)

Our olive tree occasionally gets brown leaves and one day was especially bad, so we were pressed to find out why. The only problem was, there wasn’t a lot of information out there. So, I did some research and put together this guide.

Olive trees get brown leaves due to factors such as underwatering, overwatering, nutrient deficiencies, pests, diseases, and environmental stress. To maintain healthy olive trees, ensure proper watering, provide balanced nutrients, monitor for pests and diseases, and protect from extreme temperatures.

So, while olive trees get brown leaves for several reasons, how can we tell what’s causing it, and how can we fix it? Let’s take a closer look.

Improper Watering

When it comes to olive trees, proper watering is crucial to keep the leaves green and healthy. Both underwatering and overwatering can cause the leaves to turn brown.

Underwatering

Olive trees are drought-tolerant plants, but they still need consistent moisture, especially during the growing season. If the soil becomes too dry, the leaves may turn brown and eventually fall off.

To avoid this, I water my olive trees deeply and infrequently, allowing the soil to dry out slightly between waterings. I usually check the soil moisture by sticking my finger about 2-4 inches into the ground, making sure it feels like a wrung-out sponge before watering again.

Overwatering

On the other hand, overwatering can lead to root rot, which can cause the leaves to turn brown as well. Olive trees are susceptible to waterlogged soil, so it’s essential to ensure proper drainage. When planting my olive trees, I always make sure the soil has good drainage by mixing in some sand or grit, and I avoid planting in areas where water tends to accumulate.

Mulching

Mulching is another way to help maintain consistent soil moisture. I like to add a 2-3 inch layer of organic mulch, such as straw or wood chips, around the base of my olive trees. This not only helps retain moisture but also suppresses weeds and regulates soil temperature.

2 inches of compost under the tree’s drip line every 1-2 months also does wonders.

To recap, make sure to water your olive tree deeply and infrequently, allow the soil to dry slightly between waterings, ensure proper drainage, and consider using mulch to maintain consistent soil moisture.

Improper Nutrients

Nutrient Deficiency	Leaf Symptom
Nitrogen	Entire leaf is pale or yellow
Iron	Dark green veins, rest of the leaf is yellowing
Zinc	Yellow blotches
Manganese	Broadly pale leaves, foliage color looks mottled or smeared

Just like us, olive trees need a balanced diet to stay healthy. Brown leaves may indicate a deficiency in one or more essential nutrients. Here are some common nutrient deficiencies and their symptoms:

• Nitrogen (N): A lack of nitrogen can cause the leaves to turn pale green, then yellow, and eventually brown. Nitrogen is essential for healthy leaf growth, and without it, the tree struggles to produce chlorophyll. To address nitrogen deficiency, I like to apply a balanced organic fertilizer or compost rich in nitrogen.
• Potassium (K): Potassium deficiency can lead to brown leaf tips and edges, as well as a general decline in tree vigor. Potassium plays a significant role in regulating water and nutrient movement within the tree. To fix a potassium deficiency, I apply potassium-rich fertilizers, like potassium sulfate or wood ash, being careful not to overdo it.
• Iron (Fe): Iron deficiency in olive trees can cause interveinal yellowing, which eventually turns the leaves brown. This problem is more common in alkaline soils, as iron becomes less available to the plant. To tackle iron deficiency, I either apply iron chelates to the soil or use a foliar spray containing iron.
• Magnesium (Mg): Magnesium deficiency can cause interveinal yellowing similar to iron deficiency, but it usually starts from the lower leaves and progresses upward. I correct magnesium deficiency by applying Epsom salt, which contains magnesium sulfate, either by mixing it with water and watering the plant or as a foliar spray.

To maintain the overall health of your olive tree and avoid nutrient deficiencies, I recommend using a balanced organic fertilizer or compost that provides all the essential nutrients in the right proportions.

To see which fertilizer I use and recommend, see my recommended fertilizer page.

Conducting a soil test can also be helpful to identify any specific deficiencies and guide you in amending the soil as needed.

Pests and Diseases

Olive trees can fall prey to various pests and diseases that cause browning of the leaves. Here are some common culprits and how I deal with them:

• Olive Scab or Leaf Spot (Spilocaea oleagina): This fungal disease causes small, circular, brown spots with a yellow halo to appear on the leaves. In severe cases, the leaves may turn entirely brown and drop off. To control Olive Leaf Spot, I prune my trees to improve air circulation, remove infected leaves, and apply a copper-based fungicide or whey spray as a preventative measure.
• Verticillium Wilt (Verticillium dahliae): Verticillium wilt is a soil-borne fungus that can cause leaves to turn yellow, then brown, and eventually wilt. This disease is challenging to control once it has infected a tree, so prevention is key. I ensure good soil drainage, avoid overwatering, and rotate my olive trees with non-host plants to minimize the risk of infection.
• Scales: Scales are small insects that feed on the sap of olive trees, causing the leaves to turn yellow, then brown. They often secrete a sticky substance called honeydew, which attracts ants and promotes the growth of sooty mold. To control scales, I release beneficial insects like ladybugs and lacewings, apply neem oil or insecticidal soap, and prune infested branches if necessary.
• Black Scale (Saissetia oleae): This particular type of scale can cause the leaves to turn brown, curl, and fall off. It also secretes honeydew, leading to sooty mold growth. To manage Black Scale, I use similar control methods as with other scales, such as releasing beneficial insects, applying neem oil or insecticidal soap, and pruning infested branches.

Regular monitoring and early intervention are essential to keep pests and diseases under control. You can also maintain a healthy growing environment and use preventative measures like whey spray or copper-based fungicides, you can help your olive tree stay healthy and avoid brown leaves.

Environmental Factors

Environmental stress can play a significant role in causing brown leaves in olive trees. Sudden temperature changes, for instance, can be quite harmful.

Frost can damage cells, leading to browning and dieback of leaves, while excessive heat may scorch and brown them, particularly younger leaves. To combat these issues, I protect my olive trees from frost by covering them with frost cloth or blankets during cold snaps and provide shade cloth during extreme heatwaves to minimize heat stress.

Wind damage is another environmental factor to consider, as strong winds can cause physical damage to the leaves, leading to browning and tearing. I usually plant my olive trees in a sheltered location or create a windbreak using taller plants or structures to protect them from wind damage.

High soil salinity can also cause leaf browning, as excess salts in the soil interfere with the tree’s ability to take up water and nutrients. To address saline soils, I improve soil structure with organic matter, leach excess salts by applying extra water, and select salt-tolerant olive tree varieties. Conducting a soil test can help you determine if high salinity levels are an issue.

Finally, transplant shock can be stressful for olive trees, causing them to drop leaves or display browning symptoms. To minimize transplant shock, I transplant during the dormant season, handle the root ball carefully, and provide adequate water and nutrients to help the tree settle into its new location.

So, by addressing proper watering, balanced nutrients, pests, diseases, and environmental stress factors, your olive tree will most likely stop getting brown leaves.

Sources

• https://www.rhs.org.uk/disease/olive-scab
• https://www.thenorfolkolivetreecompany.co.uk/growingolivetrees/pests-diseases/

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