We have two lemon trees in our backyard, and one of them started to get yellow leaves. While we had an idea of what was causing it, I wanted to do some more research to be sure. Here’s what I found.
Lemon trees get pale or yellow leaves from over-watering, a lack of sunlight, improper nutrients (such as iron), as well as pests and diseases such as aphids and citrus greening. Ideally, only water when the top 2-4 inches of soil is dry, apply compost and organic fertilizer, and inspect leaves for signs of disease.
So, while lemon trees get yellow leaves for several reasons, how can we tell which issue is causing it, and from there—how can we fix it? Let’s take a closer look.
The most common reason why lemon trees get yellow leaves is stress from over-watering. This is especially common in soils with poor drainage.
Over time, waterlogged soil can develop mold and lead to root rot (also called Phytophthora root and crown root). Root rot slowly decays the lemon tree’s roots, turning the leaves yellow, and over time, can kill the plant (more on root rot later).
So, what’s the optimal way to water lemon trees?
The best way to water lemon trees is to only water when the top 2-4 inches of soil is dry. You can check this by pushing a finger into the soil. Water until the soil is saturated down to 2 feet deep. Additionally, provide 2 inches of compost and 4 inches of mulch such as leaves, bark, straw, or pine needles.
By watering the soil down to 2 feet, you’re providing 90% of the lemon tree’s roots with water.
Also, by only watering when the soil is dry, you’re preventing both under-watering and over-watering. This helps the plant establish water independence.
Lemon trees that are watered with frequent and light watering typically only grow extremely shallow roots. After all, why would they grow deeper roots if the water and nutrients are only on the surface?
This keeps the plant at a disadvantage as their shallow roots mean they’re poorly prepared for windy weather and droughts.
So, if you want your lemon tree to be more self-sufficient and have a better chance of surviving the occasional drought, water it only when the soil is dry and down to 2 feet deep.
However, soils that have poor drainage (common with clay soils) can complicate this process.
Generally, planted lemon trees are hard to amend as there are large volumes of soil (needing large amounts of amendments). Because of this, the best way to amend garden soil for better drainage is to apply 2 inches of compost on top of the soil every 1-2 months. Over time, the smaller particles will work their way into the deeper soil.
You can provide a few inches of mulch to help this process, but avoid excessive mulching at this time it can further lock in the moisture in the poorly draining soil and cause more yellow leaves.
On the other hand, potted lemon trees with poor drainage can be amended fairly quickly by repotting them with fresh potting soil. Since the roots are limited to the pot, they generally don’t get as much transplant shock as digging up planted lemon trees with spread-out and established roots.
But, what if we’re watering our lemon tree correctly? What do we check next?
2. Improper Nutrients
Excess nutrients are typically caused by over-fertilizing lemon trees. This can lead to the lemon tree’s roots chemically burning, causing the tree stress and developing yellow leaves. Normally, fast-release fertilizers are the cause of over-fertilization as compost isn’t potent enough.
Lack of Nutrients
|Entire leaf is pale or yellow
|Dark green veins, rest of the leaf is yellowing
|Broadly pale leaves, foliage color looks mottled or smeared
A lack of nutrients also causes stress for the tree, which then develops yellow leaves. Insufficient nutrients are commonly caused by poor soils, leaching, and other stressors.
Nutrient leaching is when the soil has too much drainage or is over-watered and the nutrients seep too far down into the soil, out of reach of the tree’s roots.
The Best Way to Fertilize Lemon Trees
You can choose to fertilize your lemon tree’s soil with fertilizer or compost.
Tip: Remember that lemon trees require double the nitrogen to phosphorus and potassium (2:1:1). For example, a fertilizer with a 6-3-3 NPK works well.
Generally, while chemical fertilizers have nutrients in quantity, organic fertilizer and compost have quality nutrients. What this means is that over the short term, chemical fertilizers can outperform organic fertilizers and compost, but over the long term, they often cause soil damage.
This damage commonly leads to dry soil and decreased pest and disease resistance.
On the other hand, organic fertilizer and compost provide more than sufficient nutrients, increase water retention, and promote healthy soils. For example, every 1% increase in the soil’s richness (organic matter) leads to 20,000 more gallons of water absorbed per acre (source).
Either way you go, if you’d like to see which fertilizers I recommend, check out my recommend fertilizer page.
Do Epsom Salts Help With Yellow Leaves?
Epsom salts contain magnesium and sulfur and are often thought to treat magnesium deficiency in lemon trees (shown as yellow leaves with green veins). However, Epsom salts are a fast-release fertilizer and can overwhelm other nutrients in the soil. For best results, use a slow-release fruit tree fertilizer.
To learn more about why Epsom salts are bad for lemon trees, see my other post: Are Epsom Salts Good For Fruit Trees? (The Surprising Truth).
Aside from nutrients, keep in mind that lemon trees need a balanced soil pH between 6.0 to 7.0.
A slightly acidic pH is required to dissolve the nutrient solids and make them accessible to the lemon tree’s finer roots. Without a balanced pH, nutrients are “locked” in the soil which can lead to issues such as yellow leaves (especially iron).
Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution. Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils.Donald Bickelhaupt, Instructional Support Specialist, Department of Forest and Natural Resources Management
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 lemon 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 lemon tree’s soil is too acidic (below 6.0), add alkaline materials such as wood ash, charcoal, or lime.
Additionally, cold and/or wet soils are not good at promoting nutrient uptake as the lemon tree will either be slightly dormant during the cold or too stressed in wet soils.
If you’re growing your lemon tree in a container, aim to have at least a 5-gallon pot as the tree’s roots need a bit of room to spread.
3. Lack of Sunlight
Lemon trees generally require at least 6 hours of sunlight to photosynthesize properly. Without it, their leaves turn yellow and they’re unable to develop sugars for the plant. Over time, this low energy leads to the plant’s declining health, and eventually, the tree can die.
Here are some ways to boost sunlight for your lemon tree.
- Plant the lemon tree in a south-facing direction for maximum sunlight (north-facing if you live in the southern hemisphere)
- Plant the tree along a south-facing wall to reflect more sunlight and heat onto the tree (some heat even persists into the night).
- Prune some overstory trees that are blocking the lemon’s canopy from the sun. You can also prune the lemon tree itself to allow more light to reach the mid and lower branches. This new space also increases aeration from the sun and wind—discouraging disease from spreading.
Aphids & Spider Mites
The most common pest to cause yellow and curled leaves on lemon trees are aphids and spider mites.
Aphids are small bugs that suck the sap from underneath the lemon tree’s leaves and deposit honeydew (attracting ants). The leafs’ loss of sugar and moisture causes them to curl, yellow, and drop. If left unchecked, aphids can damage the lemon tree’s health and potentially stunt or kill the tree.
These bugs come in multiple colors including white, yellow, or black, and usually are found hiding underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the plant, they can compromise its health and therefore reduce fruit size and yield.
Spider mites are similar to aphids as they also feed on the plant’s leaves. However, unlike aphids, you can see signs of spider mites on the top of the leaves.
“The first evidence of mite feeding — which usually can be seen on the top of the leaf — is a yellow or whitish spotting of the leaf tissues in areas where the mites are feeding on the lower leaf surface.”University of Nebraska – Lincoln
Fortunately, the solutions to get rid of aphids and spider mites are the same:
- Spray the leaves with a jet of water (this worked for me)
- Spray neem oil (a natural insecticide made from the neem tree)
- Encourage ladybugs (a natural predator of aphids)
For example, when my potted Kaffir lime tree had aphids, I found that a jet of water was sufficient to blast them off and prevent them from coming back. All I did was remove the hose nozzle and used my thumb to increase the pressure. Just keep in mind that too strong of a blast can damage the leaves.
You can attract ladybugs to your garden (and help fend off the aphid and spider mite population) by planting companion plants such as yarrow, fennel, and dill.
To learn more about lemon tree pests and how to manage them, check out this resource by the Government of West Australia.
Root rot, also called Phytophthora Root & Crown Rot, is a root fungus that causes lemon tree leaves, blossoms, and fruit to droop, yellow, brown, and drop. It also causes yellow spots.
This disease typically occurs in areas with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant young trees with fresh soil if necessary. Raised beds are also helpful in improving soil drainage.
There is no chemical control available for crown and root rot in the home garden. The most important control strategy is careful water management.Clemson University Cooperative Extension Service
My potted Kaffir lime tree had root rot recently, which I was able to tell based on the sopping wet soil and swampy smell. Fortunately, after repotting the tree with fresh potting soil and waiting a few days, the tree made a full recovery!
Citrus Greening disease (Candidatus Liberibacter asiaticus) is the most harmful lemon and citrus tree disease worldwide. Common symptoms include yellow leaves, spotted yellow leaves, hard or inedible fruit, dead twigs, and stunted trees.
This disease is spread by an infected insect called Asian citrus psyllid, once it feeds on the leaves, it transmits the disease to the tree. And once a tree is infected, there is no cure. The majority of citrus trees infected die within a few years.
Citrus Greening disease is currently active in California, Florida, Georgia, Louisiana, Puerto Rico, South Carolina, Texas, and the U.S. Virgin Islands. This is why it’s important not to transport citrus trees or fruit to other areas.
If you’d like more information about Citrus Greening in your area, I recommend contacting your local USDA cooperative extension office.
A Note on Pesticides, Fungicides, and Herbicides
We recently had an issue with caterpillars eating our basil plants and we were about FED UP. Every time we’d plant basil plants, the caterpillars ate it.
Fortunately, we found an organic spray at our local nursery that’s made from fermented rum. The day after spraying, we’d find dead caterpillars on the soil.
If you’d like to find out more about this organic spray, you can find it here on Amazon.
So, what’s my point here?
Even though chemical sprays and fertilizers are easy, there are often long-term costs. Namely to the plants, soil, and surrounding beneficial life.
Before using chemical sprays, weigh the pros and cons and consider trying organic or permaculture-based treatments first!
To give you a head start, Stefan Sobkowiak – The Permaculture Orchard has a great video on a safe, homemade, and more importantly—effective fungicide (hint: the secret ingredient is whey).
Also, check out how Mark Shepard uses a method called STUN (Sheer-Total-Utter-Neglect) to help his berries, fruit, and nut trees THRIVE.
While the yellow leaves on our lemon tree appeared to be an iron deficiency, I’ve heard zinc and manganese deficiencies can have a similar look. So, to be safe I applied 2 inches of compost, organic fertilizer, and 4 inches of mulch. After 1-2 months, our lemon tree made a full recovery!
Remember, you can easily avoid over-watering by only watering when the top 2-4 inches of soil gets dry. This significantly reduces the chance your lemon tree gets yellow leaves. If the issue persists, it’s like another issue such as a nutrient deficiency.