A reader recently asked why their olive tree is getting some yellow leaves. While I had an idea, I did some research to find out more. Here’s what I found.
Olive trees commonly get yellow leaves from improper watering, poor drainage, and transplant shock. Unlike other fruit trees, olive trees are tough plants and don’t require great soil or frequent fertilizing. Ideally, plant olive trees on mounds of soil and only water when the top 2-4 inches of soil gets dry.
While olive trees get yellow leaves from several issues, how can we tell which one is causing it, and from there—how can we fix it? Let’s take a closer look.
In this article:
- Improper Watering (& Drainage)
- Transplant Shock
- Lack of Nutrients
- Diseases
1. Improper Watering
Compared to other fruit trees (such as apples, cherries, and peaches), olive trees are far less sensitive and require less care when watering and fertilizing.
“If olive trees are having problems, one of the last things likely to be causing it is a nutritional deficiency.”
Paul Vossen, Farm Advisor, University of California Cooperative Extension
But while olive trees can thrive with poor soil, they still grow best with regular watering. This is why the most common reasons olive trees get yellow leaves are from under or over-watering.
The best way to water olive trees is to only water when the top 2-4 inches of soil gets dry. You can check this by pushing a finger into the soil. The goal is to have soil moisture similar to a wrung-out sponge.
This is called the “Finger Test” and it prevents both under and over-watering.
Under-Watering
While olive trees are natively from Mediterranean or dry climates and are highly drought-tolerant, they grow and fruit best when watered regularly.
You can tell if your olive tree is under-watered if you see the below symptoms:
- Yellow Leaves
- Curled Leaves
- Brown Leaves
- Dropping Leaves
- Soil Feels Bone Dry
When under-watered, olive trees can’t provide sufficient water to their leaves. The leaves then start to discolor, dry, and curl to conserve moisture. If not watered soon, the leaves continue to dry until they turn brown and drop from the tree. Eventually, the olive tree dies.
Here’s how to fix under-watered olive trees:
- Water when the top 2-4 inches of soil is dry (water down to 2 feet as 90% of the roots grow here)
- Apply 2 inches of compost every 1-2 months
- Provide 4 inches of mulch every 3-6 months
Compost provides essential nutrients, increases water retention, and promotes healthy soil. For example, every 1% increase in the soil’s organic matter (compost) holds an additional 20,000 gallons of water per acre.
Mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. It also provides extra nutrients and suppresses weed growth.
By following these three steps, you’re not only ensuring your olive tree gets the proper amount of water, but you boost its water retention. With this, you’re making your olive tree more drought-tolerant and reducing the amount of care you need to provide your tree.
But what happens if your olive tree’s soil stays sopping wet for more than 24 hours?
Over-Watering
Olive trees that have too much water, or “wet feet”, get issues such as poor aeration and even root rot (more about this later).
Here’s how to tell if your olive tree is over-watered:
- Yellow Leaves
- Dropping Leaves
- Sopping Wet Soil for Over 24 Hours
- Soil Smells Swampy
The best way to avoid over-watering is to only water when the top 2-4 inches of soil is dry. By checking the soil before watering, you significantly reduce the chance of over-watering.
However, if your olive tree’s soil is staying sopping wet for 1-2 days, it has a drainage issue and needs to be amended.
Poor Drainage
Poor drainage is one of the primary causes of yellow leaves. This is because excess water blocks nutrients from being absorbed and also leaches nutrients from the soil (diluting and pushing them too deep, out of reach of the tree’s roots).
Over time, waterlogged soil drowns the plant’s roots and causes root rot, which quickly kills the olive tree.
Here’s how to fix olive trees with poor drainage:
- Check – See if the soil is staying sopping wet for 1-2 days. If it’s smelling like a swamp, root rot is likely setting in and you need to act quickly.
- Test – If you’re not sure about the drainage, you can also do a percolation test. To do this, dig a 1-foot by 1-foot hole, place a yardstick in, and fill it with water. Well-draining soil should be around 2 inches per hour.
- Amend – If you determine your olive tree’s soil has poor drainage, it needs to be amended. Potted olive trees should be repotted with fresh potting soil. Planted olive trees should have compost mixed into their soil. Compost not only retains the proper moisture but breaks up the larger clumps of soil.
Avoid mulching olive trees with poor drainage. In this case, it reduces evaporation and makes the issue worse. Once the soil is well-draining, apply 4 inches of mulch every 3-6 months.
Another way to fix poorly draining soil is to plant the olive tree on a mound of soil. This way gravity pulls the excess water from the mound. Planting in a raised bed or container are other good methods.
If you’d like more information about how to dry out wet soil, see my other post: The 7 Quickest Ways to Dry Out Garden Soil
2. Transplant Shock
If your olive tree was recently planted or repotted, and it’s starting to die, it’s likely due to transplant shock. Transplant shock occurs when a plant is exposed to a new environment and has to establish a new root system.
Avoid transplanting olive trees unless necessary as it can take up to 1 year for recovery.
To help avoid transplant shock, I like to plant with the following steps in mind:
- Have the new ground (or pot) prepared
- Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the plant’s stem and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the plant in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the plant as before
- Apply 2 inches of compost and 4-12 inches of mulch to the top of the soil
- Water generously and add more soil as needed
3. Improper Nutrients
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 |
It’s also possible the olive tree has a magnesium deficiency. This is normally seen by yellow leaves with green veins.
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 yellow leaves.
However, providing your olive tree with decent soil and nutrients does help it grow and fruit better.
Also, a lack of nutrients is still possible for olive trees, and you’ll begin to see symptoms such as leaves curling, yellowing, browning, and dropping.
So, here’s how to fix olive trees with insufficient nutrients:
- 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
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
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.
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
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 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
While the above conditions lead to yellow leaves, if your olive tree has yellow, brown, or black spots it’s likely peacock spot disease.
Peacock spot (Spilocaea oleaginea) is a fungal disease that causes olive tree leaves to get brown and black spots with yellow rings around the spots. 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 involves using 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.
Final Thoughts
After helping the reader, they reached back out and said their olive tree was getting yellow leaves from a lack of water. After using the finger test and watering when the soil is dry, their olive tree started to make a recovery.
Remember, if you haven’t planted your olive tree recently, watering is the most common reason olive trees get yellow leaves. After that, it’s a lack of nutrients, followed by peacock spot (if it has spots on its leaves).
If you’ve tried the above steps and your olive tree is still declining, see my other post: 3 Quick Steps to Save a Dying Olive Tree
Sources
- https://www.oliocarli.us/magazine/secrets-of-quality/growing-an-olive-tree
- https://www.oliveoilsource.com/page/site-selection
- 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/
