Avocado Tree Leaves Turning Brown? Here’s The Fix 

The thought of growing an avocado tree may feel like a far-off, tropical dream. However, these evergreen trees are surprisingly simple to maintain once established. 

One common problem that befalls many avocado trees is the appearance of brown leaves. This is a well-known issue among commercial growers but can throw many home gardeners for an unpleasant loop.

In this article, I’ll explain 10 of the most likely causes of avocado tree leaves turning brown. I’ll also offer some expert advice to keep your avocado tree’s foliage looking healthy year-round.

Why Do Avocado Tree Leaves Turn Brown

In USDA hardiness zones 9 through 11, the avocado tree makes a wonderful landscape plant. In cooler climates, this orchard species can be grown as a foliar houseplant (though is unlikely to ever bear fruit).

Avocado trees are naturally evergreen. This means that they do not drop their leaves in the fall as many other tree species do. It also means that their leaves do not change color with the seasons.

When avocado leaves turn brown, it’s a fairly clear sign that something is wrong with the tree or its environment. For example, the cause of your avocado tree’s brown leaves could be the result of improper watering, weather damage, or nutritional deficiency. Or it could be a sign that your tree is ill, infested with pests, or entering old age.

10 Reasons Avocado Leaves Turn Brown

The sight of brown leaves on your indoor or outdoor avocado tree is not a reason to panic. However, I strongly recommend getting to the root of the problem as soon as possible to prevent further stress or lasting damage. 

Below you’ll find the 10 most common causes of avocado tree leaves turning brown and how to fix them:

1. Lack Of Water

Mature avocado trees need about 2 inches of water per week. If these needs aren’t met, brown foliage is one of the most likely symptoms to appear.

A severely underwatered avocado tree may present with brown leaf margins that are dry to the touch. The leaves may also curl up or inwards. 

In my experience, avocado leaves tend to turn yellow and droop before the more serious symptoms mentioned above occur. It’s best to address watering issues as soon as mild symptoms appear — you don’t want to wait for the leaves to turn brown before taking action.

Avocado trees benefit from deep, infrequent irrigation. The top few inches of soil should dry out between waterings. This advice applies to both in-ground and container-grown trees.

For the best results, tailor your watering practices to your avocado tree’s unique needs. Your avocado will naturally need more water when the weather is hot and dry. Young trees often need more frequent watering than mature trees. 

Note that avocado trees grown in outdoor containers can dry out incredibly fast and require constant monitoring during the summer months.

2. Nutrient Deficiencies 

Phosphorus and potassium deficiencies can cause brown, necrotic spots on avocado tree leaves. These spots typically appear on the tree’s oldest leaves and are paired with general chlorosis (yellowing). 

potassium deficiency
Potassium deficinecy in avocado leaves

Avocado trees also need micronutrients like iron, zinc, manganese, and boron. Deficiencies of any of these nutrients can trigger brown discoloration of the leaves.

Most avocado trees respond well to citrus tree fertilizers. I recommend testing the soil around your avocado plant to determine which, if any, nutrients it currently lacks. Applying fertilizer without first testing the soil could result in overfeeding.

3. Excessive Levels Of Chloride Salt In Soil

Chloride salt buildup in the soil is a particularly common reason avocado leaves turn brown. This phenomenon is known as tip burn because the discoloration tends to affect the tips of the leaves first. Avocado trees are more likely to experience tip burn late in the growing season.

Chloride is one of the most common elements found in water. It’s found in practically all natural water sources, including rain and groundwater. 

Some water sources contain more chloride than others. For example, the mineral composition of the surrounding rocks can affect the chloride levels in groundwater. According to the University of California, the areas where avocados are often grown tend to have high levels of chloride in their water sources.

Avocado trees are noticeably more sensitive to chloride and other salts than many other plant species. Your avocado trees might develop symptoms of salt buildup while the rest of your garden remains perfectly healthy.

Avocado leaves turning brown.
Avocado leaf displaying the tell tale signs of tip burn
Image Ecoesref by cc4.0

Most of us associate the word “salt” with the stuff we use to flavor our food. However, sodium chloride is just one example of chemical salt. Many of the nutrients contained in fertilizers also take the form of chemical salts. These compounds can build up in the soil over time if too much fertilizer is applied. 

High levels of salt in the soil are best fixed with deep watering and light fertilizer applications. Watering deeply around your avocado trees will flush many chemical salts out of the top layers of soil. Applying 10 to 20% more water than your avocado tree actually needs is a great way to transport chemical salts away from the root system.

4. Cold Weather or Frost Burn

Avocado trees are infamously sensitive to cold temperatures. Even cold-hardy cultivars will only tolerate conditions down to 20°F. 

Frost can damage the leaves, stems, and fruit of an avocado tree. Avocado leaves may turn rust-brown after exposure to freezing temperatures. Depending on the size of the tree and the extent of the frost, you might notice that the outer leaves are more damaged than those inside the canopy.

The best strategy to prevent cold damage is to only grow avocado cultivars that can easily survive in your climate. However, this won’t always protect against extreme, one-off weather events.

Keep in mind that once frost damage occurs, little (if anything) can be done until the following spring. Avocado growers should instead take steps to protect trees prior to any cold weather.

I recommend moving container-grown avocado trees indoors to prevent frost damage. In many cases, relocating a potted tree to a shed or garage will suffice for a few days. Protect large and in-ground trees by wrapping the canopies with frost blankets or burlap. 

5. Humidity

For many plants, high heat and humidity go hand in hand. Avocado trees are one such example and grow best when the ambient humidity is at or above 50%.

Brown leaf margins are a frequent symptom of low humidity. Note that the visible signs of low humidity are very similar to those caused by underwatering. Insufficient watering can also exacerbate humidity problems, and vice-versa.

Humidity problems tend to be most common with avocado trees grown indoors. While the average household humidity is appropriate for most avocados, some homes are drier than others. Keep your potted avocado tree in a humid room or set up a portable humidifier nearby.

6. Scorching

Excess sun exposure can cause damage to avocado trees and their leaves. This might seem counterintuitive since trees require sunlight to convert energy. However, it’s a surprisingly common problem when transplanting young trees or relocating potted avocados.

Trees previously grown in greenhouses or indoors aren’t able to tolerate intense sunlight. To prevent scorching, it’s best to let new avocado trees slowly acclimate to life in full sun. 

Some avocado growers build temporary shade around transplants using semi-sheer fabric. Depending on the size of the sapling, this can easily be done using a set of bamboo stakes or metal fence posts. You can remove the shade structure once the tree is established in its new location.

For avocado trees grown in containers, you can physically move the pot from partial shade to full sun over the course of a week or more. If symptoms of sunburn appear, it’s a clear sign that the tree needs more time to adapt.

7. Pests Feeding on Leaves

Pests tend to target the fruit of avocado trees rather than the foliage. However, there are still a couple of species that can trigger brown leaves on avocado trees.

Avocado lace bugs (Pseudacysta perseae) are very small, winged insects that live and feed on the underside of leaves. Early signs of infestation include dark spots on the underside of avocado foliage. These spots are made up of eggs, larvae, and excrement. Established infestations eventually lead to brown spots on the top of the leaves.

The Western avocado leafroller (Amorbia cuneana) is a caterpillar that damages both citrus and avocado trees. Its common name comes from the fact that young caterpillars create shelter out of rolled foliage and silk. A tree infested with these caterpillars may develop brown leaves that have been stripped down to a thin membrane or just the veins.

Several types of mites can infest avocado trees. If your avocado plant is affected by mites, you’ll likely notice small dark flecks on the underside of leaves. 

I recommend applying horticultural oil to avocado trees to prevent infestations of these and other pests. Chemical pesticides might be appropriate in some cases as well. 

8. Fungal Diseases

Commercial avocado orchards are vulnerable to both bacterial and fungal diseases. In my experience, however, home growers are more likely to encounter fungal infections. The most common fungal diseases that cause brown leaves on avocado leaves are anthracnose and verticillium wilt.

An avocado tree infected with anthracnose will develop dark spots on the leaves and fruit. Over time, the leaves may turn completely black and fall from the tree. This fungus can travel extremely far on the wind, causing some infections to seemingly appear out of nowhere. If left untreated, this type of infection can kill an avocado tree within 2 years.

Verticillium wilt is a disease that affects countless plant species. In avocado trees, the most common symptom is the sudden dieback of leaves and small branches. Browning is often concentrated in the tips of the leaves. Verticillium wilt is often transferred between plants via contaminated tools.

Anthracnose can be treated using a chlorothalonil- or copper-based fungicide. There is no effective chemical treatment for verticillium wilt. Even in cases where fungicides are appropriate, the use of preventative measures is the most effective strategy against these diseases. 

9. Root Rot

Root rot — most often caused by the fungus Phytophthora cinnamomi — doesn’t just affect avocado foliage. However, leaf discoloration, wilting, and premature dropping are some of the earliest signs a tree might be suffering from this disease.

Root rot damages the root system and prevents the uptake of water. An avocado tree suffering from this disease will develop leaves with brown tips. It’s easy to confuse this condition with either underwatering or chloride salt buildup. 

Once established in the roots, P. cinnamomi is extremely difficult to treat. Prevention is the most effective treatment option. Only plant avocado trees in areas with adequate drainage (container-grown trees should have ample drainage holes) and avoid overwatering.

Fungicides containing potassium phosphonate may slow the progression of existing root rot. There’s also evidence that moderate applications of nitrogen can improve avocado trees’ resistance to P. cinnamomi.

10. Seasonal Changes or Tree Age

A few brown leaves here and there is nothing to worry about for an avocado tree that is otherwise healthy. This is a natural part of the growing and aging process. It’s very similar to how an animal sheds its fur or how we shed dead skin cells.

With that said, avocado trees don’t normally lose all of their leaves in the fall. Avocados are evergreens and should retain the majority of their foliage year-round.

If you notice an unusual amount of discoloration or your avocado tree starts to drop leaves at an alarming rate, I recommend examining the tree and its environment for potential problems. 

Removing Brown Leaves On Avocado Trees

Generally speaking, trees can take care of themselves. There’s no need to remove leaves that have turned brown from old age, environmental stress, or physical damage. These brown leaves will naturally drop from the tree on their own.

I do, however, advise removing leaves and limbs that show signs of fungal infection or extensive pest activity. This can prevent the spread of such problems to the rest of the tree. 

Always use sterile tools when removing branches from your avocado tree and re-sterilize everything when you’re finished. It’s best to destroy plant material that might be infected with a disease to prevent inadvertently spreading pathogens to nearby plants (I don’t recommend composting or mulching diseased branches).

FAQ Brown Leaves on Avocado Trees

Citation

The University of California – Avocado and Salts

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.