We have a few avocado saplings, and while they’re doing fairly well, we’ve noticed they started developing brown tips at the end of their leaves. After looking it up online, this “tip burn” seems to be a pretty common issue with avocado plants. So, I did some research to find out more and how to fix our avocado trees with brown leaves. Here’s what I found.
Avocado trees most commonly get brown leaves from under-watering. Other causes are sunburn, frost, or using water that contains too much salt or chlorine. The best way to prevent and fix brown leaves on avocado trees is to let tap water sit 4.5 days for the chlorine to evaporate and deep water 4 inches at a time.
So, while avocado trees can commonly get brown leaves from under-watering, what are some other causes, and what can be done to fix it? Let’s take a closer look.
It’s important to know that a small percentage of brown leaves on avocado trees is normal and won’t impact the health or fruit yield of the tree. Generally, the common figure shared by avocado growers is no more than 10% of leaves should be brown. If it’s higher than that, then keep reading and we’ll see what we can do to fix this!
Under-watering avocado trees can lead to brown leaves since the roots don’t have enough moisture to provide and cool the leaves. By having sufficient moisture in at least the first 4 inches of soil, the avocado roots can remain cool and hydrated while also cooling and hydrating the rest of the plant.
You can tell if you’re under-watering your avocado plant if the top 2-4 inches of soil are bone-dry. If this is the case, the best way to sufficiently water avocado trees is by deep watering.
To deep water, provide 4 inches of water to your avocado plants every 2-4 weeks. The goal is to get the 4 inches of soil moist. Make sure the soil doesn’t stay sopping wet for more than 24-48 hours otherwise root rot can develop.
If you live in a hot and dry climate, you may need to provide deep watering more often. If your soil is getting dry too quickly, consider mulching with leaves, bark, or pine needles to improve water retention in the soil.
Deep watering is also a best practice in general as most plants prefer it to shallow watering. This is because deep watering mimics rainfall. Since avocado trees are tropical, they’re used to a climate with long, heavy rains, not short, shallow ones.
Watering your avocado tree with only a shallow amount can cause a few unintended issues:
- Promotes shallow roots (the roots grow where the water is)
- Shallow roots aren’t drought-resistant and anchor the tree poorly
- Doesn’t flush salt from the soil
Lastly, when watering, make sure to water the full width of the soil under the canopy, not just the base of the tree.
Sunburns can also cause brown leaves on avocado trees. Simply—they become dried out. While it’s difficult to tell if the sun is causing browning leaves, start with checking the tree’s watering first, followed by sun, frost, and then checking the salt and chlorine in the water.
If you’re providing enough water to keep the soil moist, and the tree is still getting brown leaves, check that the tree isn’t getting blasted by the sun.
Like other tropical fruiting trees, avocados do best with full sun. However, the sun in tropical regions can be harsh. For this reason, consider checking on your avocado tree during the hottest part of the day. Check the leaves and the top 2-4 inches of soil for overheating or dryness.
If you believe the sun is too strong for your avocado tree and is likely drying the leaves (and turning them brown), then consider the following adjustments:
- Mulch the base of the avocado trees to increase water retention in the soil and prevent the roots from drying out from the sun. You can apply 1-2 inches of leaves, bark, or pine needles. Make sure the mulch is at least 3 inches away from the avocado stem or trunk to prevent mold or disease from spreading to the tree.
- Provide the avocado tree with sunlight from a northern exposure. While southern exposure provides more sunlight, sometimes it can get too hot for the plant.
- Additionally, give the tree some afternoon shade as this is the hottest part of the day. You can use a large umbrella, or strategically place it near bigger trees that will cast some shade during the afternoon.
Frost can also kill avocado leaves and turn them brown. Compared to the other causes, the main way to tell if frost is damaging your avocado tree is if the leaves are both browning and curling. Generally, try not to allow your avocado trees to experience weather that’s under 25ºF if possible.
While avocado trees can survive a quick period of light frost, if you get a longer or heavier frost, then consider covering outdoor avocado trees with sheets or bringing any potted avocado trees indoors until the frost is over. For hardiness zones 8 and below, you can also provide avocado trees with a greenhouse.
High Salt Content
Salt and chlorine buildup is especially common for potted avocado plants since they have a limited amount of soil to work with. Because of this, small amounts of salt and chlorine can quickly become potent. Generally, Hass avocados are more affected by this than Reed or other varieties.
Salt that’s accumulated in the soil can dry and brown the leaves on avocado trees and eventually lead to leaf drop. To remove salt from the soil, you can either use deep watering, vinegar, reverse osmosis, or chemical amendments. The easiest options to remove salt are deep watering or using a vinegar solution.
There are many types of salts found in most water sources. For context, here are some of the most common salts found in irrigation water (don’t worry, you don’t need to memorize these).
The problem with this is that when we water our plants, the salts from the water (and fertilizer) will build up over time in the soil and the leaves. When the water evaporates from the soil and the leaves, salt is left behind. The extra salt then dries out the avocado leaves starting from the tips, turning them brown.
While an excess of salt typically doesn’t affect many plants, avocado trees are particularly sensitive to it (as well as chlorine—more on this later).
Fortunately, there are a few ways you can remove or lessen the salt in the water you irrigate with.
How To Reduce Salt in Soil
- Deep watering
- Reverse osmosis
- Chemical amendments
By far the easiest and most feasible way to reduce or remove the salts in water is by deep watering (also called leaching). By providing your avocado tree with deep watering, you’re using the excess water to dissolve the salt and disperse it further into the soil (ideally beyond 3-4 feet, which is a common depth for roots).
In case you missed it, I provided some information on how to deep water in the “Under-Watering” section above.
Some other ways to flush the salt from the soil are to use vinegar, reverse osmosis, or by adding chemical amendments. While deep watering and vinegar are fairly easy to do, reverse osmosis and chemical amendments are a bit more complex.
We’ll cover more about reverse osmosis later, but for now, let’s take a look at which chemical amendments would help remove the salts and how to test for salts.
- Calcium chloride
- Sulfuric acid
- Iron sulfate
- Aluminum sulfate
- Lime-sulfur solution
Again, I wouldn’t recommend this option for beginners. However, if you are interested in pursing chemical amendments for your avocado tree’s soil, know that I haven’t tested any of these amendments personally, so I’d suggest consulting this article by Texas A&M University to learn more.
How To Test Salt in Soil
If you believe you have a salt buildup in your soil and would like to test it to confirm, you can send it 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.
On the other hand, if you’re interested in conducting a salinity test at home, then check out this video by NDSU Soil Health to see how it’s done (I wasn’t able to find the soil salinity tester she used, but I found a similar one on Amazon. It’s a little pricey, but it could be worth if you have a stubborn salinity issue).
High Chlorine Content
Chlorine is commonly used to treat tap water, so it’s not too surprising that tap water can contain high amounts of it. Like salt, chlorine can build up in the avocado tree’s leaves and soil, causing the leaves to burn and brown. To remove chlorine from tap water, use a charcoal filter or let the chlorine evaporate.
Some types of water have less chlorine than others. Here are some examples of high and low chlorinated water.
|High Chlorine Water||Low Chlorine Water|
|Irrigation water||Chlorine-evaporated water|
|Most other treated waters||Charcoal-filtered water|
Note that if you simply use rainwater to water your avocado tree, you can skip this section. However, if you water with pretty much any other method, you may find this next part helpful.
How To Reduce Chlorine in Water
There are two easy ways to remove chlorine from tap water.
- Charcoal filters
One of the easiest ways to remove chlorine from tap water is to let the chlorine evaporate. Generally, this means leaving the water to sit uncovered for 4.5 days. The greater the surface area, the faster the evaporation will occur. You can also boil the water first to speed up this process.
Additionally, you can use a charcoal filter to remove chlorine. Brita filters have a charcoal filter and will work fine for this purpose.
However, keep in mind that while these two methods remove chlorine, they don’t remove chloramines. Because of this, there’s still a small chance your avocado tree can get chemically burned and have brown leaves.
So, while chlorine-evaporation and charcoal filters are a good first step (and might be the only thing your avocado tree needs), consider adding a second step of performing reverse osmosis to completely remove the chloramines.
Reverse osmosis systems can be expensive, so first check to see if your avocado tree gets better with chlorine-evaporated or charcoal-filtered water. If these methods don’t help, then consider adding reverse osmosis as well.
I personally don’t have a reverse osmosis system, but my cousin has one and swears by it. If you’re interested, here it is on Amazon.
However, if you’d like to test the amount of chlorine in your water first, you can learn more from this video by Acuro Organics Limited.
Our avocado trees ended up growing green leaves again by first letting the chlorine evaporate from the water and then providing deep waterings. This helped remove both the salt and the chlorine as well as solving any under-watering issues.
Again, the process to remove both salt and chlorine simultaneously is to leave the water sit for 4.5 days (removing the chlorine) and then provide 4 inches of water (dissolving the salt in the soil).
Remember, it’s normal for up to 10% of the leaves to be brown. You shouldn’t need to do anything unless the percentage is higher than this. Lastly, there’s no need to prune the brown-tipped leaves off of the plant. The remaining green on the leaves still functions and the leaves will shed on their own if needed. This makes for a great mulch and can benefit other plants in the garden, especially if you have companion plants for your avocado trees!