Olive trees commonly get curling leaves from improper watering, climate, and nutrients. However, transplant shock and diseases such as root rot can also cause it.
Depending on the issue, leaves can curl up or down. They can also turn yellow or brown, indicating a deficiency or dryness.
For best results, water when the soil is dry and apply 2 inches of compost and 4 inches of mulch.
Our olive tree had some dropping and curling leaves recently and we weren’t sure what was causing it. We checked online, but couldn’t find a great resource. So, we did some more research and put together this guide. Here’s what we found.
1. Under-Watered
The most common reason why olive tree leaves curl is a lack of water. This issue is fairly easy to identify as the soil will likely be bone dry. If the soil is dry for too long, the tree’s leaves begin to dry, curl, brown, and drop.
The best way to water olive trees is to only water when the top 2-4 inches of soil is dry. I like to check this by pushing a finger into the soil, under the plant’s canopy.
When watering, make sure to soak the soil down to at least 2-3 feet as the majority of the roots are located at this depth.
Along with properly watering, compost and mulch go a long way to retaining water in the soil.
Compost provides valuable nutrients and retains moisture in the soil. Every 1% increase in the soil’s richness or organic matter leads to an additional 20,000 gallons of water held per acre.
Mulch reduces evaporation, regulates soil temperature, and prevents soil erosion. Since olive trees evolved as understory plants in forests, they’re used to plenty of mulch in the form of fallen branches and leaves.
Apply 2 inches of compost and 4 inches of mulch under the canopy. Keep the materials at least 3 inches from the olive tree’s trunk to avoid mold buildup. Reapply compost every 1-2 months and mulch every 3-6 months.
2. Extreme Heat
As olive trees are natively from Mediterranean climates, they prefer warm and dry (but not desert) weather. Because of this, they grow best in USDA Hardiness Zones 9-11.
Tip: If you live in the US, it’s helpful to know your USDA hardiness zone and find the plants that are most compatible with your climate.
However, when olive trees are exposed to weather that’s too hot, they get stressed and begin to show symptoms such as:
- Curling Leaves
- Brown Leaves (or Browning at Tips)
- Wilting Leaves
- Dropped Leaves
Let’s take a closer look at how to care for olive trees in hot and dry climates:
Tips for Hot Weather
If your olive tree is commonly exposed to temperatures 95ºF and above, the heat is likely causing the curling leaves.
Before we jump into the different ways to keep your olive trees cool, it’s helpful to know how they cool themselves in the first place:
- Send moisture from their roots to their leaves
- Transpiration (exhaling moisture from their leaves)
Now that we know these methods, let’s use them to our advantage:
- Water – Water only when the soil is dry, but don’t let it get bone dry—especially in hot weather. Use the finger test and try to maintain the soil moisture similar to a wrung-out sponge.
- Shade – Provide at least 2 hours of afternoon shade (from the western sun). You can use umbrellas, other trees, structures, or shade sails. Don’t over-shade—give your olive tree at least 6 hours of daily sunlight.
- Compost – As mentioned, compost is great at retaining moisture in the soil. Apply 2 inches of compost every 1-2 months.
- Mulch – Follow up by putting 4 inches of mulch on top of the compost. Reapply the mulch every 3-6 months. Keep both the compost and mulch at least 3 inches from the trunk to prevent mold.
- Density – Using transpiration, planting your olive trees with other plants increases the humidity around them and keeps them cooler. A great way to do this is by growing olive tree companion plants.
3. Improper Nutrients
Excess Nutrients
Excess nutrients (over-fertilizing) chemically burn the olive tree’s roots, causing stress and leading to poor growth as well as decreased flowering and fruiting.
Normally, fast-release chemical fertilizers are the cause of over-fertilization as organic fertilizers and compost aren’t potent enough.
Lack of Nutrients
Olive trees are much tougher than other fruit trees (especially apples, pears, and peaches) and easily grow in poor and even rocky soil.
Because of this, nutrients are likely one of the last reasons olive trees get curling leaves.
According to Paul Vossen, Farm Advisor for the University of California Cooperative Extension, the only common nutrient deficiency olive trees get is nitrogen. While potassium and boron deficiencies are possible, it’s highly uncommon.
| Nutrient Deficiency | Leaf Symptom |
|---|---|
| Nitrogen | Yellow Tinge and Poor Growth |
| Potassium | Light Green Leaves or Brown Tips |
| Boron | Small Leaves, Brown Tips, Short Branches |
In rare cases, olive tree can get a magnesium deficiency. This is normally seen by yellow leaves with green veins.
However rare it is, a lack of nutrients is still possible for olive trees. With it, you’ll begin to see symptoms such as leaves curling, yellowing, browning, and dropping.
So, while nutrients aren’t the likely cause for the curling leaves, it’s probably best to cover our bases and provide our olive trees with decent soil and nutrients to help them grow and fruit better.
How to Fertilize Olive Trees
- Provide proper watering and drainage (promoting proper nutrient uptake)
- Apply 2 inches of compost every 1-2 months
- Provide fertilizer 1-2 times per year
Providing the proper drainage and watering allows olive trees to absorb sufficient nutrients from the soil, while compost and fertilizer replenish nutrients in the soil (and promote beneficial soil life such as earthworms and mycorrhizal fungi).
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
Each fertilizer has different potency, and as a result, different instructions. To see the olive tree fertilizers I use and recommend, see my recommended fertilizer page.
Recommended: Are Epsom Salts Good For Fruit Trees? (The Surprising Truth)
Imbalanced pH
While nutrients are important, they’re next to useless if the soil does not have a proper pH. This is because a slightly acidic pH is necessary to dissolve the nutrient solids in the soil and make them accessible for the plant’s finer roots.
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.
Donald Bickelhaupt, Instructional Support Specialist, Department of Forest and Natural Resources Management
Olive trees do best with a soil pH between 5.0 and 8.5.
For context, most other fruit trees prefer a soil pH of 6.0-7.0, so olive trees are incredibly forgiving with soil quality and pH. However, your olive tree can start to have issues if its soil pH is below 5.0 or above 8.5.
Two good ways to check your soil’s pH are either by using a pH strip or a pH meter. I prefer using a pH meter since they’re affordable and easy to use. To see which pH meter I use and recommend, check out my recommended tools page.
If you find that your olive tree’s soil is too alkaline (above 8.5) you can add acidic amendments such as coffee grounds, sand, and peat moss. On the other hand, if your olive tree’s soil is too acidic (below 5.0), add alkaline materials such as wood ash, charcoal, or lime (ground limestone).
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the olive tree will either be dormant during the cold or too stressed in wet soils.
4. Diseases
Root Rot
You can typically tell if your olive tree has root rot if the soil is staying sopping wet for more than 1-2 days and starts smelling swampy. Allowing the soil to dry out or repotting olive trees with fresh potting soil are the best ways to amend this disease.
Root rot kills off the olive tree roots, which stresses the plant and causes symptoms such as fruit, flowers, and leaves curling, yellowing, browning, and dropping. If not addressed, it leads to stunted growth or a dying olive tree.
There is no chemical control available for crown and root rot in the home garden. The most important control strategy is careful water management.
Clemson University Cooperative Extension Service
For example, I noticed my potted Kaffir lime tree had root rot as its soil smelled swampy and was staying wet for many days at a time. In this case, I repotted it with fresh potting soil, and the tree quickly recovered.
Peacock Spot
Peacock spot (Spilocaea oleaginea) is a fungal disease that causes olive tree leaves to get curled leaves as well as brown and black spots with yellow rings. After some time, the leaves drop from the tree. The tree’s flowers, fruit, and growth are also affected.
This disease is most common in the fall when it’s warm and wet, and is usually found in coastal climates.
Treatment typically involves a spray. To learn more about which sprays are recommended for peacock spot, contact your local cooperative extension office.
Alternatively, Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and more importantly—effective fungicide (hint: the secret ingredient is whey). You can see his video below.
Sources
- https://cesonoma.ucanr.edu/files/27175.pdf
- https://ipm.ucanr.edu/agriculture/olive/phytophthora-root-and-crown-rot/
- https://ipm.ucanr.edu/agriculture/olive/peacock-spot/
