We have a few avocado trees and they sometimes get yellow leaves, which quickly drop off the tree. To get to the bottom of this, I did some research. Here’s why avocado trees get yellow leaves and what we can do to fix it.
Avocado trees most commonly get yellow leaves from overwatering which can lead to root rot, or from seasonal leaf drop, which occurs in late spring. Other reasons avocado trees get yellow leaves are a lack of nutrients, pests, disease, or insufficient sunlight. After the issue is corrected, the tree will grow new leaves.
As long as your avocado tree’s yellow leaves generally amount to less than 10% of its total leaves, you shouldn’t worry about it. This is commonly a normal event that occurs about once a year (more about seasonal leaf drops later).
However, if it seems like a larger amount of leaves are affected, then keep reading to see which issues could be causing it, and what we can do to fix it!
Overwatering
By far one of the most common reasons avocado trees have yellowing leaves is overwatering (which is often caused by poor drainage).
The best way to water avocado trees is to mimic their native tropical environment: provide sandy, well-draining soil and deep watering.
You can also keep the avocado tree elevated on a mound or raised bed and provide 4 inches of water every 2-4 weeks. It’s also important to let the soil dry in between waterings.
Avocado trees are native to tropical and subtropical environments, so they’re used to loose, sandy soils, heavy rains, and consistently warm temperatures. This can be a problem if you’re trying to grow avocado trees in clay soil, or in drier or cooler climates.
Generally, avocado trees are more sensitive and have shallower roots than other fruit trees.
Their roots can make things a bit complicated because even though they absorb shallow water, too much shallow watering without proper drainage can quickly lead to overwatering and Phytophthora root rot.
Avocado trees like watering that’s closer to rainstorms—less frequent, heavy watering. The only problem is that if the tree’s soil has poor drainage it can quickly become overwatered.
Because of this, it’s important to fix the soil’s drainage first before moving on to deep watering your avocado tree. This is especially true for avocado trees that are planted in clay soil.
Solutions
1. Improve Drainage
As mentioned, the best way to improve the soil’s drainage is to keep the tree’s soil elevated (letting gravity help drain the soil). You can do this by planting the avocado tree on a hill, mound, or in a raised bed.
If your avocado tree is already planted or potted and you’re considering amending its soil, avoid digging up the tree or repotting it unless necessary. This often leads to transplant shock and causes more issues.
Instead, add amendments on top of the soil.
Adding sand, and perlite, and even using hugelkultur works well (this even works in containers and raised beds!). These materials will work their way into the soil over time and increase drainage.
On the other hand, if you find your soil’s drainage is fine, but the top of the soil is drying out too fast (for example, from a hot day or strong wind), then I highly recommend mulching it.
In fact, I recommend mulching the soil regardless of climate since it’s such a beneficial practice.
Here are some of the benefits of mulching:
- More water retention
- Quality nutrients
- Weed prevention
- Erosion resistance
Adding mulches such as leaves, bark, or pine needles can greatly improve your avocado tree’s soil and even make it so you need to water less (and sometimes you won’t need to water at all!).
Again, make sure the soil drains well before adding mulch. Otherwise, it will have an even harder time drying out.
2. Deep Watering
Deep watering is the practice of thoroughly soaking the soil instead of only watering the first few inches, which most conventional gardening practices and sprinklers do.
Avocado trees benefit from a deep watering of about 4 inches every 2-4 weeks. Make sure to check that the soil is dry before watering again.
There are two ways to check when to water your avocado tree:
- Push a finger in the first 2-4 inches of soil to see if it’s still wet
- Use a moisture meter to check the deeper soil (generally about 10″ deep)
As you may have guessed, watering every 2-4 weeks is a general guideline. There are actually many factors that go into how often you water.
Here are a few:
- Soil drainage
- Rainfall
- Sun
- Wind
- Depth of roots
- Flowering or fruiting season
For example, cloudy days, poor soil drainage, and a younger tree means the soil retains a lot of water and will need less watering from you.
On the other hand, a strong sun, high winds, and good soil drainage mean the soil will dry out much faster and need more watering.
While these might be a lot of variables, knowing when to water is fairly simple.
While using a finger test to check the soil is quick and easy, you’re not able to see if the deeper soil or rootball is staying soaked. For this reason, consider using a moisture meter to check the wetness of the soil at the edge of the canopy, in addition to the soil around the rootball.
If you’d like my recommendation for a soil moisture meter, check out my recommended tools page.
Again, make sure the soil is drying slightly between waterings. The roots need an occasional break from the water to aerate, or breathe, properly.
If you’ve checked that your avocado tree’s soil is draining well, and you’re watering a good amount, the next most likely cause of yellow leaves is the age of the leaves.
Age of Leaves (Seasonal)
An avocado tree’s leaves can yellow and drop if the leaves have run through their lifecycle. Generally, avocado trees shed some leaves in late spring to early summer, usually from April to June.
This seasonal leaf drop is normal, and can seem like a lot of leaves are shed. However, new, green leaves will quickly grow.
If you’re within April-June, and you’ve ruled out any other cause of yellow leaves, consider waiting 1-2 months to see if the leaves improve and new, green ones come in.
Also, if you’ve already fertilized, avoid fertilizing again.
If you’d like to amend the soil while you wait, the best thing to do in this case is to provide a good layer of compost and mulch. I recommend a 2 inch layer of compost and a 4-12 inch layer of mulch such as leaves to protect the soil and provide a steady supply of nutrients.
Remember to only mulch if the soil is draining well.
Additionally, the older leaves will sometimes have brown tips. Again, if there seems to be an excess number of them (over 10%), try to identify what could be causing it.
Lack of Nutrients
While avocado trees getting yellow leaves from a lack of nutrients is less likely than the other causes, it’s still possible. Especially if you have clay soil or haven’t fertilized the tree yet.
Avocado trees prefer fertilizers with double the nitrogen (an NPK ratio of 2:1:1), which is the same as citrus trees. Generally, store-bought fertilizers are used in the early spring, while organic ones, such as compost, are used every 1-2 months. Check the soil pH to help the nutrients get absorbed properly.
The most common nutrient deficiencies avocado trees get are nitrogen, iron, and zinc.
Fortunately, these are fairly easy to fix as avocado tree fertilizer is identical to citrus tree fertilizer (see below).
If you aren’t familiar with avocado tree fertilizer, there are two routes you can take:
- Use a chemical fertilizer
- Use an organic fertilizer or compost
Chemical vs Organic Fertilizers
While chemical fertilizers are still popular in the conventional gardening world, they can sometimes do more harm than good.
Not only do organic fertilizers provide higher-quality nutrients, but they promote soil life—including earthworms and beneficial microbes.
These soil organisms then benefit avocado trees by:
- Aerating the soil
- Breaking down nutrients
- Increasing water retention
- Limiting pests and disease
Additionally, by providing a higher quality fertilizer, you don’t have to worry about nutrient deficiencies of the tree nearly as much. Instead, you can focus on applying the fertilizer as needed and let the tree take care of the rest.
While it can be tough to figure out which fertilizer is good for your avocado tree, I recently did some research and testing on some of the best fertilizers.
To see which avocado tree fertilizers I recommend, you can check out my recent post where I reviewed the best avocado tree fertilizers.
If you have a severe issue with yellow leaves, among other issues, and you’d like conclusive results on the soil’s nutrients, consider having a lab or your local cooperative extension service analyze it.
On the other hand, if you have tried fertilizer (or aren’t a fan of fertilizers), then know you have another option.
When in doubt, use compost.
Compost typically has a complete set of nutrients that avocado trees (and most plants) need. Combine this with mulching, and you have a magic recipe for providing high-quality nutrients while increasing the tree’s resistance to drought.
A good way to use both compost and mulch is to provide the soil with 2 inches of compost and then 4-12 inches of mulch on top.
Remember to avoid touching the compost and mulch to the stem or trunk of the avocado tree as this can introduce mold or disease. For this reason, keep them at least 3 inches away from the trunk.
Whichever way you go, don’t forget to consider the soil’s pH.
Proper Soil pH
Without a balanced soil pH, plants have a hard time absorbing nutrients properly.
Avocado trees prefer a soil pH of 5-7. Because of this, if your avocado tree’s soil pH is too acidic (below 5) or too alkaline (above 7), then consider amending it to adjust its pH.
Some organic amendments to increase a soil’s alkalinity are banana peels, wood ash, and biochar. On the other hand, organic amendments to increase a soil’s acidity are coffee grounds, peat moss, and sand.
Once avocado trees have the proper nutrients and soil pH, they’ll start growing new leaves.
Pests and Diseases
While pests and disease are a fairly rare occurrences, there are some ways to tell if these two are causing the yellow leaves on your avocado trees:
- Tree bark is cracking or oozing sap
- Small holes in the trunk
- Small bugs underneath the leaves
- Leaves have sporadic yellow or brown spots
Most often, it’s a good idea to prune off the diseased leaves and branches and dispose of them. When disposing of them, I recommend burning them—especially if you have many other trees (simply composting can continue the spread of pests or diseases).
There is also a common disease for avocado trees called Phytophthora, which is caused by overwatering.
If you find caterpillars are taking over your avocado tree, release parasitic wasps and they will get rid of them for you naturally.
If you believe a pest or disease is causing the yellow leaves on your avocado tree, and you’d like more information, check out this awesome visual guide by The Yard Posts.
On the other hand, if your avocado tree’s leaves don’t have spots and are entirely yellow, know that this is most likely not caused by pests or disease. Instead, reference the other sections of this article.
Lack of Sunlight
A lack of sunlight can also cause yellow to light green leaves due to the lack of chlorophyll development.
Like most fruiting trees, avocado trees prefer at least 4-6 hours of sunlight.
However, sunlight (or a lack of it) isn’t likely to cause yellowing, so if I were you, I wouldn’t spend too long considering this section.
Generally, if your tree is getting a minimum of 4 hours of sunlight a day, then it should have green leaves (my potted Meyer lemon tree still had green leaves with less than 3 hours of daily sunlight in the winter).
Final Thoughts
For our avocado trees with yellow leaves, we found that we needed to improve the drainage by adjusting the soil (we have clay soil). We did this by adding sand and compost and lightly scratching it into the top of the soil.
Avocado trees are fairly sensitive compared to other plants, so it’s normal for them to go through cycles of leaves drooping, discoloring, and even dropping.
The best thing you can do is check that your tree is getting the proper drainage, water, nutrients, and sunlight. Last, check that the tree doesn’t have any pests or diseases.
Once these potential causes are addressed, there’s a good chance your tree will soon grow a new set of green leaves.
Remember, there’s no need to prune the yellow or brown leaves (unless there’s a pest or disease). These leaves will naturally shed and become more mulch (which is great for your companion plants)!
If you still aren’t sure what’s causing the yellow leaves on your avocado tree, my recent post helps troubleshoot avocado trees and their common conditions: How To Revive a Dying Avocado Tree (3 Quick Steps).
