We have three avocado trees and while they’re doing fairly well, we noticed their leaves started browning on the tips. After looking it up, there weren’t great answers out there, so I did some research to find out more. Here’s what I found about avocado trees and brown leaves.
Avocado trees get brown leaves from a lack of water or a buildup of salts in the soil. These salts are typically caused by hard water or too much fertilizer and can be flushed out with soft water. For best results, use rainwater, avoid fertilizing in the winter, and use well-draining soil.
Let’s take a closer look at how to identify which issue is causing brown leaves on our avocado trees, and how we can fix it.
In this article:
- Under-Watered
- Over-Watered
- Extreme Heat
- Frost
- Excess Salts
- Transplant Shock
- Diseases
1. Under-Watered
Avocado tree leaves can curl and brown if they get too dry. Typically, this is from a lack of water, but extreme heat or dryness can also cause it. To prevent this, keep the tree’s soil moist and avoid exposing it to temperatures of 90ºF or more.
Use shade cloth, shade sails, umbrellas, or other trees to create shade. You can also bring potted avocado trees indoors, but avoid placing them near central heat.
Like all trees, avocado trees need to have sufficient moisture in their soil to thrive. Since they’re native to the tropics, they’re used to plenty of water and high humidity.
When starting to dry, their leaves curl or droop to conserve moisture. If not addressed, they’ll dry completely and turn brown in the process.
Of course, depending on the weather, the soil can get drier faster and require more water. This can make growing them challenging in hot and dry climates, such as New Mexico, Arizona, and parts of California.
Recommended: The Top 30 Drought-Tolerant Fruit Trees (Ranked)
So, what’s the best way to water avocado trees?
How to Fix
The best way to water your avocado tree is to only water when the first 2-4 inches of soil gets dry. You can check this by pushing a finger into the soil, up to the second knuckle. For best results, use 2 inches of both compost and mulch on top of the soil to improve water retention and reduce evaporation.
Aside from watering, it’s also important to make sure the avocado tree’s soil has proper drainage.
Too much drainage and the soil will dry out quickly. Too little drainage and the soil will hold excess water, leading to root rot and other conditions such as yellow leaves.
This is why checking your avocado tree’s soil is the best way to gauge how much water it needs. You can do this by simply pushing a finger into the soil, up to the second knuckle, and feel if the soil is wet or dry.
Soil should not be bone dry or sopping wet but have consistent moisture, similar to a wrung-out sponge.
If you find your avocado tree’s soil is draining or drying too fast (within 1-2 days), apply 2 inches of compost and 4 inches of mulch under the tree’s canopy.
Compost improves the richness of the soil, which increases water retention. For example, every 1% increase in a soil’s organic matter can help hold 20,000 gallons more water per acre.
Mulch drastically reduces evaporation from the soil and protects it from drying in the sun and wind. Soil can easily bake from strong sunlight, while high winds can act as a blow dryer.
The goal is for the soil to hold moisture for at least a few days, and ideally for a week.
If your avocado tree is potted and indoors, make sure not to place it near any central heat vents (I accidentally did this to my potted Meyer lemon tree and it caused more brown leaves and leaf loss).
While this might be a lot of information, these techniques will help make sure your avocado tree receives the right amount of water.
In short, use the finger test and water only when the soil is dry. Add compost and mulch as needed to protect the soil from drying out too fast.
Compost can also usually replace fertilizers (more on this later)!
2. Over-Watered
While over-watering avocado trees can lead to brown leaves, it’s more likely to lead to green or yellow leaves being shed. Under-watering (drought stress) is a far more likely cause of brown leaves on avocado trees.
You can tell if your avocado tree is over-watered by:
- Brown leaves
- Yellow leaves
- Dropped leaves
- Soil is sopping wet for over 24 hours
Over-watering can be caused by many factors but it’s the most common with clay soils or those with poor drainage.
For example, clay soils have tightly packed particles, preventing the soil from draining well. This leads the avocado tree’s soil to hold water for days at a time. This causes other issues such as root rot (a fungal disease that typically requires replanting the tree).
The most common reasons why avocado trees get over-watered are:
- Watering too frequently
- Clay soil
- Poor drainage
- Watering during rainstorms
How to Fix
To prevent avocado trees from getting over-watered, plant in loamy, well-draining soil and only water when the top 2-4 inches of soil gets dry.
If you check your avocado tree’s soil 24+ hours after watering it, and it’s still sopping wet, it likely has poor drainage and is getting over-watered.
How to Test Drainage
You can also test your soil’s drainage by digging a 1-foot by 1-foot hole near your avocado tree and filling it with water (percolation test). If the hole drains slower than 2 inches per hour, it has poor drainage.
Of course, this is a guideline and not a rule, so don’t worry if yours is way off. This is just a way to get a rough view of your soil’s drainage.
Just make sure to dig outside of the drip line of the tree to avoid damaging its roots. You can also do this test a couple of other times in different areas of your yard to get a better idea of your soil types.
When amending poorly draining soil, compost, sand, and perlite are great to use. Place 2 inches of any of the three amendments under the avocado tree’s canopy. Over time, these materials will work their way into the soil and promote better drainage.
Tip: Compost fixes both poor-draining and fast-draining soil as it breaks up the larger clumps of clay as well as retaining the right amount of water.
Once the soil is well-draining, apply 4 inches of mulch every 3-6 months.
Also, avoid transplanting or repotting your avocado tree, unless the tree has root rot and is dying. If you need to repot your potted avocado tree for better drainage, use fresh potting soil.
3. Extreme Heat
If your avocado tree is commonly exposed to temperatures 90ºF and above, it’s likely causing the brown leaves. Extreme heat, or leaf scorch, often causes avocado leaves to dry and brown at the tips. If left for too long, the entire leaf will brown.
Avocado trees grow best in USDA hardiness zones 8-11, which typically range from subtropical to tropical.
Tip: You can find the USDA hardiness zone you’re in with this map from the USDA.
Because they grow in warmer climates, avocado trees are normally exposed to hot, and sometimes dry weather, for much of the year. Combine this with a lack of water, and they can’t properly cool themselves.
Before we jump into ways to keep your avocado trees cool, it’s helpful to know how they cool themselves:
- Send moisture from their roots to their leaves
- Transpiration (exhaling moisture from their leaves)
How to Fix
Using this knowledge, here are some ways to help your avocado tree stay cool:
- 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 keep 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 avocado 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 the compost. Reapply the mulch every 3-6 months.
- Density: Using transpiration, plant your avocado trees with other plants to increase the humidity around them and keep them cooler. A great way to do this is by companion planting.
But what happens if your avocado tree is properly watered and protected from the heat? What else could be causing its brown leaves?
4. Frost
If your avocado tree is frequently getting to 32ºF and below, it’s likely getting brown leaves from the cold. As avocado trees are native to the tropics, they’re not used to frost. So, when a frost does come by, it often significantly damages the tree.
How to Fix
Here’s how to keep your avocado trees warmer in times of frost:
- Cover: Covering your avocado tree’s canopy significantly reduces wind chill and provides a barrier to frost. Bedsheets are an affordable and common material to cover avocado trees.
- Mulch: Insulate your avocado tree’s soil with 4-12 inches of mulch. If you want, you can even add 2-4 feet of mulch. This helps prevent the ground (and roots) from freezing.
- Wrap: While the canopy and roots are protected, you can also protect and insulate the trunk by wrapping cardboard or another insulating material around it.
- South: If you live in the northern hemisphere, the southern sun is the hottest. So, if cold is a concern for your avocado trees, plant them on the south side of your property or plant along a south-facing wall to reflect heat onto the plant.
- Potted: Bring your potted avocado tree inside if it gets too cold. Remember, avoid placing it near your central heat as it can dry the leaves out quickly.
Tip: Avocado trees grow best in USDA Hardiness zones 8-11 (ideally 9-11). So, if your trees are frequently dying from frost, and you’re in zone 8 or below, consider planting more cold-tolerant fruit trees such as plums, peaches, and apricots.
5. Excess Salts
Avocado trees are one of the most sensitive fruit trees, and a buildup of salts in the soil can accumulate in the tree’s leaves and chemically burn them.
Fun Fact: This issue has been documented since at least 1951.
Leaf burn of avocado is caused by sodium or chloride accumulation in the leaf, or by inadequate water supply.
A. D. Ayers, D. G. Aldrich, and J. J. Coony, California Agriculture 1951
Generally, these salts are accumulated from hard or treated water (such as tap water). Over-fertilizing can also lead to excess salt in the soil. To reduce salt buildup, avoid fertilizing in the winter, flush the soil, and use rainwater if possible.
Let’s take a closer look at what causes salt buildup in the soil and how we can reduce (and fix) it.
Hard Water
Just like how we perform better with healthy food and clean water, so do trees. While we’ll cover fertilizer and nutrients in the next section, what exactly makes water clean (or dirty)?
Tap and irrigated water are often heavily treated with added minerals and chemicals, which then accumulate as the water evaporates—leaving salts in the avocado tree’s soil. Most commonly, these excess salts are chlorine and sodium salts.
Salt accumulation is more common with potted avocado trees as they have a limited amount of soil to work with. This is because planted avocado trees have much more soil and benefit from getting regular flushes from rainfall. More salt can also build up if the soil has poor drainage.
Since the solution is similar to that of over-fertilizing—I’ll include them both together below.
Over-Fertilizing
Salts can build up in soil if you provide your avocado tree with excess fertilizer. While avocado trees are evergreen, and not too dormant in the winter, they still benefit from a break from fertilizers during this time. If the soil has poor drainage, it can be easily overpowered by fertilizers.
Like hard water, fertilizers contain different chemicals and salts, all of which can accumulate in the soil. This can especially be a problem if the avocado tree gets a potent and frequent dose of fertilizers.
How to Fix
The best ways to reduce salt buildup in the soil are to flush the soil, use rainwater, and switch to compost. You can flush the soil by watering for 5 minutes. If rainwater is not possible, you can use reverse osmosis water or let the tap water sit for 4.5 days for the chlorine to evaporate.
These are the 3 best ways to reduce salts from building up in your soil:
- Flush the soil
- Water with soft water
- Switch from chemical fertilizers to compost
Flushing the soil will help dissolve the salts and push them further down into the soil (or drain out of the pot). A good way to do this is by watering the soil under the avocado tree’s canopy for 5 minutes with soft water.
Rainwater is the best soft water to use and trees absolutely love it (more on soft water below).
While chemical fertilizers can be convenient and are easy to use at scale, they have many downsides including damaging the soil and tree’s health. If using fertilizers, use organic, slow-release fertilizers when possible and follow the instructions and amount listed on the package.
Avocado trees do best with a fertilizer that has twice the nitrogen to phosphorus and potassium (NPK), such as an NPK of 6-3-3. Compost is also a great source of nutrients.
If you’d like my recommendation for the best avocado tree fertilizers, check out my recent post: The Complete Guide to Fertilizing Avocado Trees (& The Top 3 Options).
Alternatively, you can use compost, which not only provides a rich supply of nutrients to the tree but also promotes beneficial soil life and helps retain water.
How To Get Soft Water
Rainwater is simply the best water to use for any of your plants. Some benefits of watering with rainwater include:
- 100% soft water
- Slightly acidic
- Contains nitrates
Soft water means it has little to no harsh chemicals or minerals, while the acidity and nitrates (nitrogen) are great for acid-loving avocado trees.
However, if rainwater is not possible in your area (if you have limited rainfall, live in an apartment, etc.), other methods can reduce the hardness of your water.
Reverse osmosis water is a method to purify water by using pressure to push it through special filters. While reverse osmosis systems can be a bit expensive to install, you can also buy the water separately.
For example, I buy my RO water at Whole Foods in reusable 5-gallon jugs. Even though we mostly use it for drinking, I have watered some smaller potted plants with it.
Distilled water is similar to reverse osmosis, just slightly less clean. Distilled water is essentially made by collecting steam. It’s still a great option to water your avocado trees, especially compared to tap water.
However, if you do use tap water, there are a few ways you can reduce the chemicals and salts from building up.
Chlorine is commonly found in tap and irrigated water as it helps disinfect it. Unfortunately, it also causes chlorine salts to build up. Different types of water will have different levels of chlorine.
| High Chlorine Water | Low Chlorine Water |
|---|---|
| Tap water | Rainwater |
| Irrigation water | Chlorine-evaporated water |
| Most other treated waters | Charcoal-filtered water |
Luckily, an easy way to reduce the chlorine in tap water is to let it sit, uncovered, for 4.5 days. By doing so, most of the chlorine will evaporate, which means much less for your avocado tree’s soil.
Some other ways to flush the salts from the soil are to use vinegar or add chemical amendments such as gypsum or calcium chloride. While using vinegar is fairly easy to do, chemical amendments can be a bit more complex.
How To Test for Salts in Soil
If you believe you have salts that built up in your soil and would like to confirm it with a test, you can send a sample out to a testing laboratory. I’m not sure about other states, but here in Texas, you can send your soil sample to the Texas A&M AgriLife Extension Service.
6. Transplant Shock
If your avocado tree was recently planted or repotted, and it has drooping leaves, brown leaves, or is dying, 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 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 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
7. Diseases
Root Rot
Root rot kills off the avocado 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 avocado tree.
You can typically tell if your avocado tree has root rot if the soil is staying sopping wet and starts smelling. Allowing the soil to dry out or repotting avocado trees with fresh potting soil are the best ways to amend this disease.
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.
Verticillium Wilt
Verticillium wilt is a fungus that is similar to root rot in that it usually occurs in soils with excess water. Additionally, over-fertilizing can also cause it.
The most susceptible fruit crops that contract verticillium wilt are nightshade (tomatoes, peppers, and eggplants), but other fruiting plants such as avocado trees can also be infected. Symptoms of this disease include leaves wilting, yellowing, and dropping, and potentially branch dieback.
Prevent and treat verticillium wilt by pruning infected branches, avoiding excess water and fertilizers, and following best gardening practices.
Should You Remove Brown Leaves on Avocado Trees?
If your avocado tree’s leaves are completely brown and are ready to fall off, it’s okay to lightly pick them off of your tree. However, if only the tips are brown, it’s best to leave them on the tree. Any green on the leaf can still photosynthesize and help feed the tree.
Final Thoughts
Today, I’m letting my tap water sit for several days to reduce the chlorine and feeding my plants with compost instead of chemical fertilizers. Because of this, my avocado trees are doing much better, but I’m still keeping an eye on them and seeing if they get any other brown or dropping leaves.
If they get brown leaves in the future, I now know to check the amount of water they get, if it’s hard or soft water, and if they have any other buildup of salts!
