My parents have a lemon tree that occasionally gets yellow leaves on it. While we didn’t think much of it at first, we noticed it started to get worse and some of the leaves would also fall off. So, I did some research to help them out and find what’s happening to their lemon tree. Here’s what I found.
Lemon trees typically get yellow leaves due to overwatering. However, issues such as pests, disease, and a lack of nutrients can also cause this issue. The best way to resolve yellow leaves on lemon trees is to check (in order) the watering, nutrients, and any pests or disease and apply the appropriate solutions.
So, while the most common reason why lemon tree leaves turn yellow is due to overwatering, it could be caused by a few other issues. To help reverse yellow leaves on your lemon tree, we’ll take a further look at the tree’s preferred watering and nutrients, as well as how to identify and avoid the most common pests and diseases. Let’s get into it.
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Why Lemon Tree Leaves Turn Yellow
The most common reason why lemon tree leaves turn yellow is from overwatering. While lemon trees are fairly resilient, they’re also a bit picky when it comes to their soil and watering.
Lemon trees prefer loose, well-draining soil that gets watered 1-2 times per week. Since lemon trees are a subtropical species, they’re used to heavier and longer rainfalls. Because of this, they prefer deep watering sessions instead of shallow. This helps the tree grow deeper roots and access deeper water tables.
If you were like me when I first started gardening, you might have watered your plants every time you checked on them. Unfortunately, this can drown the roots, which causes a variety of issues and can most commonly lead to yellow leaves. Let’s take a look at one of the best ways to water a lemon tree and make sure yellow leaves don’t develop.
The Best Way To Water Lemon Trees
Deep watering is the practice of slowly soaking the soil so the water penetrates further into the ground. Shallow watering only wets the top 2-4 inches of soil, so the tree’s roots have little incentive to grow any deeper. This can cause problems such as poor anchorage and a higher dependency on more frequent waterings.
By deep watering, the tree is encouraged to grow deeper roots to access all of the water. Its deeper roots provide several benefits:
- Better anchorage (especially in high winds)
- Access to deeper water tables
- More water retention in the soil
- Reduces soil erosion
- Increases overall soil health
Once the lemon tree grows deeper roots, accessing deeper water tables means that you can water it less, and sometimes—you don’t have to water it at all!
The roots also hold more water in the soil, which not only benefits the lemon tree but nearby plants as well. Because water evaporation is reduced, the soil can provide a more reliable source of water to neighboring plants.
Naturally, the roots protect the soil by holding it together, which reduces the effects of wind, rain, and sun erosion on the soil.
Because the lemon tree’s roots provide increased water and aeration, and reduced erosion, life in the soil can benefit from a richer environment. The types of life include beneficial microbes and earthworms, which in turn, provide nutrients for the lemon tree.
However, it’s important not to overwater the lemon tree as this can lead to yellow leaves created from stagnant water and fungus such as root rot (more on this later).
The best rule to follow when watering a lemon tree is to only water when the top 2-4 inches of soil are dry. Typically, this means watering 1-2 times per week, but it depends on the tree’s size, soil, and weather.
You can push a finger in the soil to test the soil’s moisture, or use a moisture meter. To see which moisture meter I recommend, you can check out my recommended tools page.
On the other hand, if you find that your lemon tree’s soil is dry and under-watered, its leaves could start to dry, brown, and fall off.
If you’d like more information about watering lemon trees, make sure to check out my recent post: How Much Water Lemon Trees Need (With Real Examples).
The second most common reason why lemon trees get yellow leaves is from poor nutrients in the soil. This is typically due to infrequent or too synthetic fertilizer applications.
Lemon trees prefer a fertilizer that has twice the amount of nitrogen to phosphorus and potassium (together making NPK, the main three nutrients for plants). So, fertilizers that have a 6-3-3 NPK, or similar, would work well. Lemon trees also need a soil pH of 6.0-7.0 to efficiently absorb nutrients from the soil.
Check the pH
Even if you have a great fertilizer for your lemon tree, if the soil isn’t the right pH, the tree won’t be able to use many of the nutrients. Because of this, it can start to develop yellow leaves and slowly die.
As mentioned, lemon trees prefer a slightly acidic soil pH of 6.0-7.0. There are a few ways you can test this (the moisture meter I linked above also detects soil pH), and if you find your lemon tree’s soil is outside of this range—don’t worry, there are ways to fix it.
One of the best ways to adjust the pH of your soil is to use homemade ingredients.
For example, if you find the lemon tree’s soil is too acidic (below 6.0) you can add some banana peels or wood ash (just make sure the ash is not processed charcoal or coal as they can contain chemicals and toxins that can damage the tree and soil).
On the other hand, if your lemon tree’s soil is too alkaline (above 7.0), add some coffee grounds, peat moss, sand, or pine needles.
But, aside from pH, lemon trees can also develop yellow leaves from an imbalance of nutrients. Let’s take a look at how to best balance nutrients in the soil.
Which Fertilizer To Use
The best fertilizer for lemon trees is one that has a 2:1:1 NPK ratio, such as a 6-3-3. If you’re new to plant fertilizers and NPK, this means the fertilizer has 6% nitrogen, 3% phosphorus, and 3% potassium. These three nutrients are the primary nutrients for just about any plant.
Other secondary elements such as calcium, sodium, and magnesium are typically included in store-bought fertilizers as well.
However, in recent times, farmers are finding that synthetic, manufactured fertilizers can sometimes do more harm than good, and can be largely unused by trees. This means much of the fertilizer will simply wash away in the rain and soil.
Because of this, there’s been a strong resurgence in organic fertilizers, along with compost.
People and farmers alike are finding that plant nutrition is eerily similar to human nutrition—the fresher the food, the more nutrients get absorbed, and the healthier the individual.
This is why compost is a great option when fertilizing. In fact, compost can often replace most fertilizers as it provides an abundance and variety of rich nutrients. The only thing to keep in mind with compost is that it’s generally slightly alkaline, so make sure to check your soil’s pH after amending it and see if you need to balance it out for the lemon tree.
Overall, using a proper fertilizer for your lemon tree will help prevent and reverse its yellow leaves (assuming it’s not caused by another issue). However, choosing a fertilizer for your lemon tree can be tricky. They’re almost all different in nutrients and have different instructions.
To keep this easy, I’ve recently created a guide on the best lemon tree fertilizers. To see which ones I recommend, you can check out my other post: The Full Guide to Lemon Tree Fertilizer (& The Top 3 Brands).
Alternatively, if you’d prefer to make your own lemon tree fertilizer from everyday kitchen scraps, you might like my guide on crafting the perfect homemade fertilizer for citrus trees.
As mentioned, root rot comes from overwatering your lemon tree or poor soil drainage. When water is stagnant, it quickly begins to create rot, and a fungus called root rot (or Phytophthora) develops. As a consequence of this, lemon tree leaves can begin to turn yellow and fall off.
If you find your lemon tree’s soil is smelling swampy, or currently has root rot, don’t worry—my kaffir lime tree once had root rot and it wasn’t too hard to fix it.
The best way to fix root rot is to stop watering the tree and let the soil dry out. When the soil dries out, the fungus will die off. However, this is a balancing act as you don’t want your lemon tree to die as well. Make sure to keep an eye on the soil and the tree’s health and see if this is working.
If this doesn’t work for you, you may need to amend the lemon tree’s soil. For planted trees, this means lightly working in some sand to improve the drainage. For potted trees (like my kaffir lime tree), simply repotting it with fresh soil will do the trick.
If you have a planted lemon tree and decide to amend the soil, remember not to dig too deeply as some of the tree’s more shallow roots can become damaged.
If your lemon tree has yellow or dropping leaves, it could have whiteflies.
Whiteflies are tiny white bugs that are related to aphids. They commonly cluster underneath leaves and feed on the leaves, resulting in a sticky honeydew. These small, and numerous wounds can introduce fungus to your lemon tree.
If the number of whiteflies gets too large, they’ll feed on too many leaves, which will affect the lemon tree’s health. Specifically, this impairs the tree’s ability to photosynthesize and obtain energy for the plant. With the leaves being mostly useless, the tree will start to shed them. Because of this, the leaves will slowly turn yellow and fall off.
Fortunately, like aphids, you can simply hose whiteflies off with a burst of water. This is best done on a strong setting on your hose’s nozzle (but not too strong as the water pressure can rip through the leaves and cause more damage). You can also fit your thumb over the hose’s nozzle to increase the amount of pressure. This will be sufficient in removing these bugs.
I’ve done this to aphids after they appeared on my kaffir lime tree and they didn’t return. Just make sure to get the underside of the leaves as well.
If hosing them off with water doesn’t work, you can try spraying the infected leaves with soapy water. This binds their movements and wings, which stops them from feeding. Because of this, they’ll soon die off.
Aphids are fairly common in most gardens, and there’s a good chance you’ll have to deal with them at some point. Similar to whiteflies, they suck nutrients from the leaves and can weaken the tree, which causes leaves to yellow and fall off.
These tiny bugs can exist in a variety of colors. The best way to spot them is to check underneath the leaves. While they might be hard to see, you can see them with the naked eye, especially when they’re in clusters.
If you see curling, yellow, or damaged leaves on your lemon tree, try checking under them to spot any clusters of white, black, or yellow dots.
Similar to whiteflies, aphids can also commonly be deterred and killed by using a blast of pressurized water or soapy spray.
As mentioned, with only the pressure of covering a hose with my thumb, I was able to successfully knock off the aphids from my kaffir lime tree. They haven’t returned since. Alternative methods to control aphids include neem oil or ladybugs (a natural predator to aphids).
More Tips To Prevent Yellow Leaves on Lemon Trees
- Avoid fertilizing leaves – Leaves are designed for photosynthesis and not for absorbing nutrients that come in contact with it. On the other hand, roots specialize in accessing available nutrients in the soil. So, stick to fertilizing the soil and not the leaves.
- Mulch – Mulching the base of lemon trees can help retain water in the soil, provide a slow supply of nutrients, and block the sun from drying the soil out. Some of the best mulches for citrus trees are pine needles, leaves, and grass clippings. Provide 1-2 inches once or twice a year. Avoid touching the mulch to the tree’s trunk as this can introduce mold.
- Compost – Similar to mulching, providing 1-2 inches of compost can be a great supplement for lemon trees, and in some cases, completely replace fertilizer. Apply the compost once at the start of the growing season and try not to let it touch the trunk directly either.
- Pruning – Pruning lemon trees is a good practice since it can train the tree to focus on a certain type of growth. For example, young lemon trees should have their flowers and fruit pinched or pruned so the tree can redirect its energy and reach a mature size faster. On the other hand, mature lemon trees can benefit from having some excess branches and foliage pruned to allow for more energy for flower and fruit development.
For more information about caring for lemon trees, make sure to check out my recent post: Lemon Tree Care: The Complete Guide (Indoor & Outdoor).