We have a few avocado trees in our backyard (Hass, Reed, and Fuerte) and while most of them are doing well, one of our Hass trees is dropping its leaves. To help fix this, I did some research and testing. Here’s what I found causes avocado trees to drop their leaves.
Avocado trees drop their leaves from improper watering, nutrients, climate, transplant shock, as well as pests and diseases. However, improper watering is the most common cause. Ideally, only water avocado trees when the first 2-4 inches of soil is dry and provide compost and mulch. Grow avocado trees in zones 9-11.
So, how can we tell which issue is causing our avocado tree to drop its leaves, and from there—how can we fix it? Let’s take a closer look.
Table of Contents
1. Under-Watering
When avocado trees are under-watered, their leaves curl to conserve moisture. If left for too long, the leaves will dry, brown, and drop. To prevent this, only water when the top 2-4 inches of soil is dry.
Like most plants, avocado trees need sufficient moisture in their soil to properly grow, develop fruit, and cool themselves in times of heat. When they don’t have enough water, they’ll shed their less vital parts, which usually include the fruit, blossoms, and leaves.
So, what’s the ideal method to water avocado trees?
The best way to water avocado trees is to only water when the first 2-4 inches of soil gets dry. The goal should be soil moisture similar to that of a wrung-out sponge. Apply 2 inches of compost and 4-12 inches of mulch for maximum benefits.
I cannot stress just how useful compost and mulch are for avocado trees (and other plants)!
Compost adds valuable nutrients and retains great amounts of water. This higher water capacity is due to compost increasing the soil’s richness. For example, each 1% increase in a soil’s organic matter can hold20,000 gallons more water per acre (source).
Mulch protects the soil and its beneficial microbes by regulating soil temperature, preventing soil erosion, and further reducing evaporation. Since avocado trees evolved in the partial shade of forests, they’re used to having a plentiful layer of fallen branches and leaves on top of their soil. Because of this, mulching is one of the BEST practices you can do for your avocado trees.
For best results, apply 2 inches of compost and 4-12 inches of mulch. Reapply compost every 1-2 months and mulch every 3-6 months. Keep these materials at least 3 inches away from your avocado tree’s trunk to prevent mold from growing.
2. Over-Watering
Avocado trees are most often over-watered from poor drainage. Symptoms of over-watered avocado trees include curling, drooping, yellowing, and dropping leaves. Additionally, waterlogged avocado trees can develop root rot—a water mold that eats away at the avocado tree’s roots.
You can tell if your avocado trees are over-watered if the top 2-4 inches of their soil is staying sopping wet after 1 hour of watering. Severely waterlogged avocado trees have water that pools towards the surface and begins smelling swampy (a clear sign of root rot starting).
Over-watering is especially common in compost soils or those with high amounts of clay. This is because the finer clay particles are compressed, preventing water from seeping into the ground. Instead, you get water pooling near the surface, drowning the plant’s roots.
Since avocado trees are natively from the tropics, they’re used to light to moderately sandy soil—which naturally promotes proper drainage.
To see a comparison of the size of sand vs clay particles, see my graphic below.
If you find that your avocado tree has poorly draining soil, here are some methods to amend it.
To amend a planted avocado tree’s soil, provide 2 inches of compost every 1-2 months and let the compost naturally work its way into the soil. While using some mulch can help in some cases, it can also prevent the waterlogged soil from drying.
To amend a potted avocado tree’s soil, repotting with fresh potting soil is the simplest and most effective option. By using new and dry potting soil, you’re providing your avocado tree with clean soil and a new source of nutrients.
More extreme cases can benefit from transplanting your avocado tree to a raised bed or mound—using gravity to assist with drainage.
However, if your avocado tree’s soil moisture is similar to a wrung-out sponge, and it’s still getting leaves dropping, it’s time to look at climate.
3. Extreme Weather
Avocado trees do best in USDA hardiness zones 8-11. However, some varieties can tolerate colder climates.
Deciduous fruit trees such as apple and cherry trees are native to temperate climates, so dropping leaves in the autumn is normal. But since avocado trees are evergreen and native to tropical climates (with little to no frost), they’re not supposed to lose their leaves.
West Indian and some hybrid varieties are best adapted to a lowland tropical climate and relatively frost-free areas of the subtropics. Mexican varieties are more cold-tolerant and not well-adapted to lowland tropical conditions. Guatemalan and Mexican hybrids are generally more cold-tolerant than West Indian x Guatemalan hybrid varieties.
Avocado Growing in the Florida Home Landscape, Jonathan H. Crane, Carlos F. Balerdi, and Ian Maguire from the University of Florida Extension
So, if you’re in Florida or another subtropical or tropical climate, grow West Indian and certain hybrid varieties.
On the other hand, if you’re in the cooler, more maritime climate such as California, grow Mexican avocado varieties.
Guatemalan varieties are also more cold-tolerant as it has some climates with high altitude.
| Avocado Varieties | Ideal Climate |
|---|---|
| West Indian | Tropical, low altitude |
| Mexican | Subtropical, medium to high altitude |
| Guatemalan | Subtropical, high altitude |
However, there are still some hot or cold spells that can come up that damage avocado trees. Here’s what to do in these cases:
Hot Weather Tips
- Provide 2 inches of compost and 4-12 inches of mulch. Since compost increases the soil’s water retention, and mulch regulates soil temperature and reduces evaporation, they’re the best ways to keep avocado trees cool.
- Shade avocado trees from the afternoon sun. Since the western, afternoon sun is much hotter than the eastern, morning sun, shade the tree for a least a few hours from its west side. Some ideas to shade are large umbrellas, shade sails, or other trees.
- Move potted avocado trees indoors during heat waves. Try to move them gradually over two weeks to not stress them out from the swing in temperature. If you can move them to a patio with partial shade, that’s even better.
Generally, while hot weather more commonly leads to brown and dropping leaves, extremely cold weather can also cause it.
Cold Weather Tips
- Insulate the tree’s canopy with bedsheets or the trunk with cardboard during times of too much frost. Plastic tarps also work well, especially in preventing ice build-up.
- Provide a mound for planted trees. Planted avocado trees benefit from a 1-2 foot high mound of mulch such as leaves to insulate the tree and its roots during the winter.
- Place avocado trees along a southern-facing wall for maximum sunlight and warmth. Generally, facing south allows for the most sunlight (north if you’re in the southern hemisphere). Also, as night falls, some warmth from the wall continues radiating onto the tree.
- Avoid placing indoor avocado trees near the central heater as it quickly dries out its leaves. I accidentally did this to my potted Meyer lemon once, and it quickly recovered after I moved it to a cooler room.
4. Improper Nutrients
Excess Nutrients
Excess nutrients are caused by over-fertilizing avocado trees. This leads to the avocado tree’s roots chemically burning, causing the tree stress and developing discolored and dropping leaves. Normally, fast-release fertilizers are the cause of over-fertilization as compost isn’t potent enough.
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 |
A lack of nutrients also causes stress to the avocado tree, which then develops discolored and dropping leaves.
Insufficient nutrients are commonly caused by poor soils, leaching, and other stressors.
Nutrient leaching occurs when soils have too much drainage or are over-watered and the nutrients seep too far down into the soil, out of reach of the plant’s roots.
The Best Way to Fertilize Avocado Trees
Fertilize your avocado tree with fertilizer or compost. If you choose a store-bought fertilizer, aim for an NPK with double the nitrogen to phosphorus and potassium. For example, use a 6-3-3 NPK. For compost, choose one of quality and freshness if possible.
While chemical fertilizers have nutrients in quantity, they typically don’t have nutrients in quality.
Even though chemical fertilizers might be sufficient over the short term, over the long term they often short-circuit the nutrient exchange between the tree and its beneficial soil life (such as mycorrhizal fungi). This leads to dry and dead soil (AKA dirt) and overall decreased plant health.
Mycorrhizal fungi promote many aspects of plant life, in particularimproved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
On the other hand, compost provides more than sufficient nutrients, increases water retention, and promotes healthy soils. Many gardeners are even finding that compost is replacing their fertilizers.
Either one you choose—you can see my recommendations for both compost and fertilizer on my recommend fertilizer page.
Soil pH
Aside from nutrients, keep in mind that avocado trees need a balanced soil pH between 5.0 to 7.0 (source).
The reason why avocado trees prefer soil with a slightly acidic pH is that it’s ideal to dissolve nutrients in the soil.
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 usinga 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 myrecommended tools page.
If you find that your avocado’s soil is too alkaline (above 7.0) you can add acidic amendments such ascoffee grounds, sand, and peat moss. On the other hand, if your avocado tree’s soil is too acidic (below 5.0), add alkaline materials such as wood ash, charcoal, or lime.
Additionally,cold and/or wet soilsare not good at promoting nutrient uptake as the avocado tree will either be slightly dormant during the cold or too stressed in wet soils.
Once avocado trees have the proper nutrients and soil pH, they’ll start growing new leaves.
5. Transplant Shock
If an avocado tree was recently planted or repotted, and it’s starting to die, it’s likely due to transplant shock. Transplant shock occurs when the plant is exposed to a new environment and has to establish a new root system.
Avoid transplanting avocado 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 tree’s current topsoil as possible, without damaging theshallow roots
- Grab the base of the tree’s trunk and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the tree in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the trunk as before
- Apply 2 inches of compost and 4 inches of mulch to the top of the soil
- Water generously and add more soil as needed
6. Pests & Diseases
Avocado trees get several different types of pests and diseases, but the most common aregrasshoppers, borers,root rot, and Verticillium wilt.The best way to reduce pests is to encourage their predators (such as lizards and birds), while fungal diseases can be treated by pruning infected leaves and applying sprays.
While diseases aren’t as likely to affect your avocado tree compared to watering, nutrients, and climate, they can still be an issue.
A good way to tell if your avocado tree has pests is if you see signs such as holes in the leaves, branches, or trunk. On the other hand, you can usually spot diseases if your avocado tree has spots on its leaves.
This article would be far too long and not a good experience for you if I provided all of the pests and diseases avocado trees can get, so I’d like to provide you with a couple of great resources if you’d like more information.
For starters, check outthis helpful articleby Plant Village, orthis guidefrom the University of California Agriculture and Natural Resources.
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