My family has some citrus trees in their backyard and for some reason, a few of the trees are getting yellow leaves. They weren’t sure what was causing it and asked if I knew anything about it. I had an idea, but I did some research to find the best answer for them. Here’s what I found.
Citrus tree leaves turn yellow due to over-watering, improper nutrients, lack of sunlight, or pests and diseases. However, the most common causes are over-watering and improper nutrients. For best results, only water when the top 2-4 inches of soil are dry and provide compost and mulch.
As you can see, yellowing leaves (also called chlorosis) on citrus trees can be caused by several issues. So, how do we identify which issue is causing it, and better yet—how can we fix it? Let’s take a closer look.
While symptoms of under-watering are leaves curling, drying, and browning, over-watering symptoms include drooping and yellowing leaves.
There are two main reasons why citrus tree leaves turn yellow from over-watering:
- Root rot
- Nutrient leaching
Waterlogging or Root Rot
First, waterlogging and root rot are caused by over-watering, but more specifically—from poor drainage.
Waterlogging is when the soil has stagnant water, often for long periods. If left long enough, the mold begins to grow in the water, infecting the tree’s roots and causing them to decay. This is often called root rot. This process could take days or weeks, which is why it’s important to catch it as soon as possible. The most common and obvious symptom of root rot is yellow leaves.
For example, a couple of years ago, I saw my potted Kaffir lime tree was getting yellow leaves. After some inspecting, I saw its soil was staying sopping wet for days and smelled like a swamp.
Drainage can be a tricky subject, especially if you’re dealing with heavy clay soils. But poor drainage can also be caused by a recess in the ground, watershed, and compact soils (common in backyards and other sites of construction).
The best way to determine if your soil has poor drainage is to do a percolation test. If you’d like to see a percolation test in action, check out this video by This Old House on YouTube.
If you do find that your soil has poor drainage there are a few things you can do.
Amending Poorly Draining Soils
Potted citrus trees can have their soil amended by repotting them with fresh soil. This is what worked for my potted Kaffir lime tree when it was getting yellow leaves from over-watering and root rot.
Generally, transplanting potted citrus trees won’t cause too much transplant shock as the pot is sufficient at containing their roots. As long as the roots aren’t tugged or damaged, there shouldn’t be much of an issue. Make sure to support the rootball when transplanting and make the process fairly quick if possible.
While transplant shock can take the tree up to one year to recover, it’s often worth it for potted citrus trees as soils with poor drainage are often the bigger problem. Citrus trees should also be repotted every 3-5 years as they outgrow their pots, preventing root binding.
On the other hand, planted citrus trees are a bit trickier when amending their soil as their roots are often spread out and their root system is established. As a result, transplanting isn’t as worth it as it means root damage is more likely. This can cause more issues such as dropping fruits and leaves, and even the tree’s death.
I’d recommend only transplanting mature citrus trees if it means they’d otherwise die if left alone.
To assist with a planted citrus tree’s drainage, allow the garden soil to dry (if possible), and provide 2 inches of compost and 4 inches of mulch. Over time, the organic materials will break down, both increasing the soil’s drainage as well as richness (holding more water without waterlogging the soil). You can use mulches such as leaves, bark, straw, and pine needles.
Once the citrus tree’s soil is well-draining, only water when the first 2-4 inches of soil are dry, and water down to 2 feet deep. This is by far the simplest and best way to water, as it prevents both under-watering and over-watering. Additionally, provide 2 inches of compost and 4 inches of mulch to the base of the tree (this can even replace fertilizers).
Compost is great at not only providing sufficient nutrients (more on this later) but increasing the soil’s richness—every 1% increase in the soil’s richness holds an additional 20,000 gallons of water per acre (source).
Mulch brings benefits such as regulation of soil temperature, reduced evaporation, and added nutrients once the mulch breaks down.
Remember to keep the compost and mulch at least 3 inches from the tree’s trunk to prevent moisture build-up (which can lead to mold on the trunk).
If you haven’t yet planted your citrus tree in garden soil, and your soil has poor drainage, it’s usually best to plant them in a mound of soil. For more information about planting in mounds (and why this is best in clay soils), check out my post: Can Fruit Trees Grow in Clay Soil (& How To Plant Them)?.
Again, if your citrus tree’s leaves are curling, drying, and browning, under-watering is the more likely issue.
On the other hand, if your soil has good drainage, but is over-watered, nutrient leaching can result.
Nutrient leaching, or nutrient runoff, is when the nutrients are carried by excess water and moved deeper into the soil, or into the waterways. As a result, the citrus tree’s roots have reduced access to these nutrients, leading to issues such as yellow leaves.
Leaching is especially common when using chemical fertilizers, even more so with the fast-release varieties.
The best way to reduce or eliminate nutrient leaching is to keep best practices, such as watering only when the soil is dry and providing compost to increase the soil’s richness—promoting proper water (and therefore nutrient) retention.
While nutrient leaching is one way your citrus tree can get insufficient nutrients, your soil might naturally have poor or excess nutrients, both of which also cause yellow leaves.
2. Improper Nutrients
Either too few or too many nutrients in the soil causes citrus trees to develop issues such as yellow leaves. Over time, the leaves begin to die, turning brown and falling off of the tree. If left long enough, the citrus tree will die.
Lack of Nutrients
The reason why a lack of nutrients turns leaves yellow is that the tree moves nutrients from the more mature leaves to the younger leaves. As a result of the nutrients leaving, the mature leaves become discolored. Over time, all of the leaves can suffer from this (mature and young).
Insufficient nutrients are typically either caused by leaching (covered above) or poor soils.
While it can be difficult to tell which nutrients your soil is lacking, here’s a table I put together that may help.
|Nutrient Deficiency||Leaf Symptom|
|Nitrogen||Entire leaf is pale or yellow|
|Iron||Dark green veins, rest of the leaf is yellowing|
|Manganese||Broadly pale leaves, foliage color looks mottled or smeared|
If your citrus tree’s leaves fit any of the above descriptions, it can be a good indicator one of those nutrients is lacking in the soil. While nitrogen is the primary nutrient plants need, iron, zinc, and manganese are important trace, or secondary nutrients.
However, this table is not black and white, as sometimes there’s a combination or range of issues and symptoms. If you’d like a more definitive nutrient profile of your soil, consider reaching out to your local cooperative extension as they commonly have soil tests available for your area.
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the citrus tree will either be slightly dormant during the cold or too stressed in wet soils.
On the other hand, an excess of nutrients typically stresses the citrus tree, by either the overstimulation of nutrients causing the yellow leaves or the chemical burning of the roots.
Again, these issues are most common from fast-release chemical fertilizers. Compost itself does not have the same concentration of nutrients, and therefore cannot chemically burn the tree’s roots.
If you do find that your citrus tree has too many nutrients (such as from over-applying fertilizer), nutrient leaching by over-watering is a good solution. In this case, provide a slow drip of water for an hour or two, saturating the soil. Many of the nutrients will be leached further down, away from the plant’s roots.
When it comes to providing the proper amount of nutrients and fertilizing your citrus tree’s soil, there are two approaches.
For citrus trees, use a fertilizer with an NPK that has double the nitrogen to phosphorus and potassium, such as a 6-3-3. Aim for organic and slow-release if possible. Alternatively, you can apply 2 inches of compost every 1-2 months under the canopy.
While it may be hard to believe, chemical fertilizers were only invented in 1903 and citrus trees have been thriving without them for hundreds and thousands of years. If you’d like to learn more about how compost can sufficiently replace and even outperform fertilizers in the long run, see my other post: Can Compost Replace Fertilizer? Here’s What the Experts Say.
Even if your citrus tree’s soil has the proper amount of nutrients, improper soil pH can also lead to yellow leaves.
Soil pH might sound a bit technical, but it’s quite simple. Soils that are high in sand typically have a more acidic pH, while clay soils are more alkaline. Other materials such as salt can contribute to the soil’s pH.
Like most plants, citrus trees prefer a soil pH of 6.0-7.0.
The reason why citrus trees prefer a slightly acidic pH is because it dissolves the nutrient solids in the soil, making them accessible to the plant’s finer roots (source).
If the soil’s pH is either too acidic or too alkaline, the nutrients cannot be absorbed easily, leading to issues such as yellow leaves. Over time, dropping leaves, flowers, and fruits can result.
Two good ways to check your soil’s pH are either by using a pH strip or a pH meter. I prefer using a pH meter since they’re affordable and easy to use. To see which pH meter I use and recommend, check out my recommended tools page.
If you find that your citrus tree’s soil is too alkaline (above 7.0) you can add acidic amendments such as coffee grounds, sand, and peat moss. On the other hand, if your citrus tree’s soil is too acidic, add alkaline materials such as wood ash, charcoal, or lime.
3. Lack of Sunlight
While not as likely as over-watering or improper nutrients, a lack of sunlight causes yellow leaves. This is due to the plant not receiving enough photosynthesis and chlorophyll (what makes a leaf green). Over time, the leaves will pale or yellow.
If a lack of sunlight goes on long enough, the citrus tree will exhaust its energy reserves and begin to decline in health. This also contributes to higher rates of infection from pests and diseases.
Ideally, citrus trees should receive at least 6 hours of direct sunlight daily.
Sunlight is essential for plants to photosynthesize—turning the light into sugars that it uses for its growth, fruiting, immune system, and more. Generally, the tops of leaves are what capture the sunlight (much like solar panels), while the bottoms of leaves are used for functions such as transpiration (similar to how humans sweat to cool themselves).
While 6+ hours of sunlight is easy to get in most places where citrus trees grow, it can be difficult in other areas, especially during the winter as the day length is reduced.
For example, at this time of writing, it’s winter here in Austin, Texas. Since it gets below freezing, I moved my potted Meyer lemon tree indoors. It gets some sunlight next to the west-facing window, but not enough to thrive long-term. However, it’s definitely a sufficient amount for the tree to survive the winter.
Keep in mind that potted plants should not be placed near the central heat as they will dry out quickly. This happened one year to my potted Meyer lemon tree and its leaves started drying and dropping. After moving it to a cooler room, it recovered and started growing again.
If your citrus tree is currently getting slightly pale or yellow leaves from a lack of sun, here are some best practices you can do to boost its sunlight:
Planted Citrus Trees
- Prune overhead trees to allow more light to reach citrus trees
- Plant citrus trees facing south for maximum sunlight and warmth (if you live in the southern hemisphere, plant facing north)
- Place along a south-facing wall to have light and heat reflected onto the tree, even into the night (again, this is north-facing for the southern hemisphere)
Potted Citrus Trees
- Place along a southern facing window
- Move to a greenhouse
- Get a full spectrum grow light
4. Pests and Diseases
Some pests and diseases cause leaves to yellow or get yellow spots. These can include aphids, whiteflies, mites as well as citrus greening disease.
If you have small insects clustering underneath your citrus tree’s leaves, they are most likely aphids. Aphids (and whiteflies) suck the sap from the leaves, causing them to quickly yellow. The best ways to get rid of aphids are by spraying them with a jet of water, using neem oil, or encouraging ladybugs (a common predator to aphids).
For example, a good plant to attract ladybugs is dill.
However, for more companion plants for citrus trees, see my other posts: The 7 Best Companion Plants for Citrus Trees and 10+ Companion Plants That Prevent Pests and Diseases.
You can generally tell your citrus tree has a disease if it has yellow spots (as opposed to solid yellow leaves), or if you’ve ruled out all of the other possible issues.
One of the most common and destructive diseases is citrus greening, which is a highly contagious bacteria (to citrus trees) that causes mottling and yellow leaves. Symptoms of citrus greening are leaf and fruit drop, as well as stunted trees and fruit. You can usually tell greening if a particular section of a citrus tree is yellowing.
For more information about citrus tree diseases, check out this resource by the University of California, Agriculture and Natural Resources.
Citrus trees with yellow leaves are most often caused by over-watering or improper nutrients, but they can also be caused by a lack of sunlight or by pests and diseases.
If you’re not sure where to start, begin with the least invasive option and move towards the most invasive. For example, changing the watering of the tree is a lot less stressful for the tree than digging it up and transplanting it.
Keep in mind that minor changes in leaf color are normal, especially when it comes to seasonal changes. This is due to the slowdown of nutrients, common in colder weather. Leaves that are discolored or dropping is fairly normal if it’s within 10-20% of the total canopy. However, any more than this should prompt some investigation.
Before you start taking action, here are some questions you can ask yourself to get some direction:
- Are the yellow leaves only on new leaves, or the mature ones too?
- Is the yellowing on part of the leaf or the whole leaf?
- What kind of soil is the tree planted in? Sandy, loamy, or clay? How’s the drainage?
Remember, healthy soil means a healthy tree! When in doubt, promote soil health to provide the citrus tree with sufficient nutrients, a healthy immune system, and optimal performance.