We have a few olive trees in our backyard and one of them is starting to die. While I had an idea of what was causing it, I did some research to find out more. Here’s what I found.
Olive trees die from stress typically caused by improper watering, climate, and nutrients, as well as pests and diseases. Ideally, only water when the soil is dry, and apply 2 inches of compost and 4 inches of mulch under the canopy. They grow best in USDA hardiness zones 9-11, which is generally between 25ºF to 90ºF.
But, how can we tell which issue is causing it, and from there—how can we fix it? Let’s take a closer look.
Can Dying Olive Trees Be Saved?
A dying olive tree can be saved if the issue is caught early and hasn’t done too much damage. For example, if under-watering is the issue, and the tree has only lost a few leaves, it’s reasonable to expect the tree to make a full recovery.
However, if the tree is drought-stressed to the point where it loses all of its leaves, it’s up to the amount of existing stored energy in the tree and roots to determine if it will survive and grow new leaves.
Pro-Tip: You can tell if your olive tree is still alive if you scratch some of the bark off or prune a small branch. If it’s green or white inside, the tree is still alive and can recover in the right conditions.
3 Steps To Save a Dying Olive Tree
If you’ve already tried finding out which issue your olive tree has, and you’ve gotten stuck, there’s still hope.
Here are 3 steps you can use to save your olive, for just about any condition.
1. Identify the Possible Issues
The first step in reviving a dying olive tree is to identify the possible issues. After all, the process of elimination wouldn’t work if we didn’t know which options we were eliminating!
If you haven’t seen them yet, reference the below sections for the top 6 most common olive issues.
2. Isolate the Actual Issue
Once you’ve checked the specific symptoms your olive has, you can now cross off potential issues from your list.
Try to get it down to 1-3 potential issues that best match the symptoms your olive tree is exhibiting. This will give you the best chance to provide the right solution for it (you don’t want to repot the plant if the problem is a watering issue).
3. Test Solutions
Now that you have a narrowed-down list of the potential issues, it’s time to try the solutions one at a time.
Start with the least invasive solution and work your way up to the most invasive. Again, it’s much easier on the plant (and you) to provide less water than to repot or transplant it. Try to save those options for last.
Continue testing the treatments you believe are most likely to fix the issue. And hopefully, one of them sticks.
Worst case scenario, start from step 1 and make a new list of possible issues. There’s a chance you might have missed something or you notice something new the second time around.
Stay persistent! It’s easy to say, “Dumb plant, why don’t you want to live?”, but there’s always a reason why plants act the way they do. Stay the course and see if you can uncover it.
If you have no idea what issue your olive tree might have, that’s okay! That’s what I’m here for. To give you a head start, let’s jump into the 6 most common reasons olive trees die.
The Top 6 Reasons Why Olive Trees Die (& Fixes)
1. Under-Watering
When an olive tree has too little or too much water for an extended period, the tree becomes stressed and begins to show signs of decline. Symptoms of under-watering are leaves curling, drying, browning, and dropping.
The best way to water olive trees is to only water when the top 2-4 inches of soil is 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.
When watering, make sure to soak the soil down to at least 2 feet deep as 90% of the tree’s roots are found at this depth.
Deep watering also promotes deeper roots, allowing the tree to become more water-independent in times of drought.
On the other hand, shallow roots are more common in trees that are water-pampered. They have a tougher time surviving when a watering session is missed or when the ground gets too hot for the shallow roots.
Provide 2 inches of compost and 4-12 inches of mulch.
Compost provides valuable nutrients and increases the water retention of the soil. For example, every 1% increase in the soil’s richness (organic matter) leads to an additional 20,000 gallons of water held per acre (source).
Mulch drastically reduces evaporation, regulates soil temperature, and prevents soil erosion. As olive trees evolved as understory species in forests, they’re used to plenty of mulch in the form of fallen leaves and branches. As permaculture guru Geoff Lawton says, “A forest grows from a fallen forest.”
To recap, provide 2 inches of compost and 4-12 inches of mulch under the tree’s drip-line or canopy. Reapply compost every 1-2 months and mulch every 3-6 months. Keep these materials at least 3 inches away from the tree’s trunk to prevent mold.
Compost and mulch are two of the most beneficial practices you can do, and by combining this with only watering when the soil is dry, you’re dramatically reducing the likelihood your olive tree gets under-watered.
However, what if you feel the soil and it’s been sopping wet for days at a time?
2. Over-Watering
You can tell if your olive tree is over-watered with symptoms such as yellow leaves, green leaves dropping, and root rot (more on root rot later).
While over-watering is possible in all soil types, it’s most common in poorly draining soils or those that are lower in the ground. This issue is compounded if the depressed soil is at the base of a hill and receives plenty of runoff.
Poor drainage is usually caused by compacted soils or those with heavy clay content. Since clay particles are much smaller than sand or silt, they easily form a tight layer that allows little to no water to pass.
Another way of checking soil drainage is by doing a percolation test.
Here’s how to do a percolation test:
- Dig a 1-foot by 1-foot hole (outside of your tree’s drip-line to avoid damaging its shallow roots)
- Place the yardstick in the hole and fill it with water
- Wait an hour and measure the amount the water drained
The ideal rate of drainage is 2 inches per hour.
Pro-Tip: Perform multiple percolation tests in different areas to get a more complete picture of your total soil drainage.
Naturally, if the percolation test is slower than 2 inches per hour the soil has poor drainage. Faster than 2 inches is fast drainage.
However, this is a guideline and not a rule, so don’t worry if yours is way off. The idea of this test is to see if your soil’s drainage is poor or quick.
What’s interesting is that poor-draining soils and fast-draining soils have the same solution—to increase the soil’s organic matter (AKA compost).
Organic matter not only breaks up the clumps of poorly draining soil but provides ideal water retention. It’s because of these effects that compost practically amends soils of all types and drainages.
In this case, I’d suggest applying 2 inches of compost every 1-2 months until the soil is amended. It can take some time, but the compost’s particles work their way into the soil and break up the clumps over time.
Avoid using mulch until the soil has sufficient drainage. Mulch can make poor drainage worse by trapping the moisture between the ground and the mulch.
Recommended: 10 Expert Tips for Watering Fruit Trees
3. Extreme Heat
Olive trees do best in USDA hardiness zones 9-11, which is generally between 25ºF and 90ºF. While some varieties can tolerate down to zone 8, olive trees are natively from the Mediterranean and prefer warmer weather.
Let’s take a look at how to care for olive trees in both hot and cold weather.
Hot Weather Tips
When olive trees are consistently in temperatures of 90ºF and above, the tree’s leaves begin to overheat. Symptoms of this include leaves curling, drying, browning, and dropping (usually in that order).
If an olive tree is already under-watered, any heat quickly compounds this, drying the tree extremely quickly. If this happens, olive trees can die in a matter of days or hours.
Before looking at solutions, it’s helpful to know how olive trees cool themselves.
Olive trees stay cool by sending moisture from their roots to their leaves and through a process called transpiration.
Much like how humans breathe and release moisture when we exhale, plants do the same. Only, this is called transpiration. This increased moisture from plants is why a forest can feel more humid than its more open surroundings. And it’s extremely helpful for plants to stay cool and not dry out.
Now, looking at solutions, there are a few things we can do to adjust the tree’s microclimate and make it more comfortable during heat waves.
- Compost and Mulch: As mentioned earlier, compost and mulch are incredibly effective practices for keeping olive trees properly watered and cool. As long as the soil stays moist and is not sopping wet, the tree can cool and support its leaves.
- Partial Shade: Using other trees or structures to provide partial shade for olives mimics their natural forest environment and gives them a break from the hot sun. Generally, it’s best to provide relief from the western sun as it’s the hottest. Even 2 hours of partial shade a day goes a long way.
- Dense Planting: By densely planting olives with other plants, more roots hold groundwater, more canopies provide shade, and more leaves increase moisture through transpiration. So, not only does the ground stay cool and moist, but the air as well! Densely planting different species also provides many companion plant benefits.
Cold Weather Tips
Because olive trees are native to warm climates, it’s best to grow them in USDA hardiness zones 9-11. This is considered tropical or subtropical. However, they also tend to do better in drier climates, such as those found in New Mexico, Arizona, and parts of the Mediterranean.
If your temperature drops below freezing for an extended period, your olive tree will likely begin to die. However, there are several things you can do to protect your olive tree from frost.
- Mulch: One of the best ways to protect olive trees from frost is to insulate their roots. To do this, use between 4-12 inches of mulch.
- Insulate: You can also insulate the rest of your olive tree and reduce ice buildup by using a bedsheet for its canopy and wrapping the trunk with cardboard or another insulating material.
- South-Facing: To maximize the sunlight and warmth for your olive tree, plant on the south side of your property (north if you live in the southern hemisphere). The southern sun is the hottest, and you can also plant near a south-facing wall or large rock to help reflect heat.
If you’d like to learn more about microclimates, check out this cool video by Gardener Scott.
4. Improper Nutrients
Excess Nutrients
Too many nutrients are often caused by fast-release chemical fertilizers as compost isn’t potent enough. When this happens, the tree’s roots can become chemically burned, causing the tree stress and leading to a decline in health.
If you believe you’ve over-fertilized your olive tree, I suggest removing as much of the fertilizer as possible via leaching. To do this, soak your olive tree’s soil to dilute the existing fertilizer and allow it to flow deeper into the soil (out of reach of the tree’s roots). You may have to do this at least a few times.
However, avoid leaching if your soil has poor drainage as the soil can become waterlogged. In this case, either apply generous amounts of compost and garden soil or repot the tree with fresh potting soil (for potted olives).
Lack of 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 |
If you haven’t fed your olive tree in the past several months, there’s a good chance it may be dying from a lack of nutrients.
Symptoms of a lack of nutrients depend on the deficiency.
For example, olive trees commonly get a nitrogen deficiency and get lightly colored or yellow leaves. This is more likely in younger olive trees as nitrogen is the primary nutrient needed for growing a canopy.
Let’s take a look at the optimal way to prevent a lack of nutrients for your olive tree.
The Best Way To Fertilize Olive Trees
If you decide to use a store-bought fertilizer, opt for one with a balanced NPK (nitrogen, phosphorus, and potassium) such as a 10-10-10. Each brand has different potencies, so follow the instructions on the label for the best results.
Alternatively, use compost. I recommend applying 2 inches of compost every 1-2 months under the tree’s drip-line or canopy. Applying mulch on top of the compost goes a lot further and adds to the water retention and nutrients.
Generally, I prefer using compost over fertilizers, and many gardeners are finding that compost is replacing their chemical fertilizers.
Either one you choose, if you’d like to see which fertilizers and compost I recommend, check out my recommended fertilizer page.
Keep in mind that while nutrients are essential, they aren’t everything.
Imbalanced Soil pH
When olive trees have an imbalanced soil pH, they can develop issues such as discolored and dropping leaves. Additionally, their flowers and fruit can drop early and the tree is more likely to develop other issues.
Olive trees prefer a soil pH of 5.0 to 8.5.
The reason olives (and most plants) prefer a slightly acidic soil pH is that it helps dissolve the nutrient solids in the soil, making them more accessible to 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 test your soil’s pH are with pH strips or a meter. I prefer using a pH meter since they’re affordable and easy to use. To see which pH I recommend, check out my recommended tools page.
However, olive trees are much more hardy than most other fruit trees, and can tolerant a wider range of soil pH (most fruit trees prefer between 6.0 and 7.0).
If you do find your olive tree’s soil is acidic (under 5.0), provide alkaline amendments such as charcoal, wood ash, and lime.
On the other hand, if your olive tree’s soil is too alkaline (above 8.5), provide acidic amendments such as peat moss, sand, and coffee grounds.
5. 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
6. Diseases
Root Rot
Root rot, also called Phytophthora Root & Crown Rot, is a root fungus that causes olive tree leaves, blossoms, and fruit to droop, yellow, brown, and drop.
This disease typically occurs in areas with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant young trees with fresh soil if necessary. Raised beds are also helpful in improving soil drainage.
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
My potted Kaffir lime tree had root rot recently, which I was able to tell based on the sopping wet soil and swampy smell. Fortunately, after repotting the tree with fresh potting soil and waiting a few days, the tree made a full recovery!
Peacock Spot
While the above conditions lead to brown leaves, if your olive tree’s leaves have 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 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.
