Lemon trees (Citrus limon) are evergreen, so their leaves typically don’t change colour with the seasons. This means that the appearance of yellow leaves — regardless of the time of year — is cause for concern.
While there are many reasons your lemon tree’s leaves might be turning yellow, few are indicative of a death sentence. Most yellow foliage can be treated and reversed if you take action right away.
In this article, I’ll discuss the most common causes of lemon tree leaves turning yellow and the best steps to take to treat each one.
- Why Are Your Lemon Tree Yellow Leaves
- What Causes Yellow Leaves on Lemon Trees
- Removing Yellow Leaves On Lemon Trees
- Verdict: Lemon Tree Leaves Turning Yellow
- FAQ Yellow Leaves on Lemon Trees
Why Are Your Lemon Tree Yellow Leaves
The technical term for leaf yellowing is chlorosis. Chlorosis is an unusual absence of chlorophyll (the compound in leaves that makes them appear green). Leaves with low levels of chlorophyll are unable to photosynthesize properly, which can have huge ramifications for future tree health.
Most cases of chlorosis are the result of environmental stressors, nutritional deficiencies, or pest activity. Both in-ground and container-grown lemon trees can fall victim to these issues, though some are more likely to affect one group of trees than others.
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What Causes Yellow Leaves on Lemon Trees
With so many potential causes of yellow foliage, diagnosing this problem can be a headache for even the experienced gardener. Below you’ll find a bit more information about common causes of yellow leaves and how to treat them.
Nutrient Deficiencies In Lemon Trees
Citrus trees are heavy feeders. If your lemon tree’s foliage is pale green or yellow, it might be due to a lack of essential nutrients.
Discoloured foliage is a relatively early sign of nutritional problems. Keeping an eye on leaf health and correcting deficiencies as quickly as possible is the best way to prevent issues with flower and fruit production down the road.
I recommend conducting a soil test to identify which nutrients might be missing. However, the presence of key nutrients is only one facet of plant nutrition. Additional factors like soil pH and moisture availability can also impact your lemon tree’s ability to take in necessary nutrients.
Several nutrients play a role in leaf colour. In my experience, these 4 deficiencies are the most likely to cause yellow leaves in lemon trees:
Nitrogen tends to be consumed in much larger quantities than other macro- and micronutrients. As a result, it’s very easy for lemon trees to become deficient in this nutrient.
Nitrogen deficiencies can present in several ways. You might notice all of your tree’s foliage turning pale green or yellow. Or you might notice that new growth appears healthy while the oldest leaves are faded. In some cases, yellow discolouration will appear only along the leaf veins.
Routine feeding with a nitrogen-rich citrus tree fertilizer is the best way to treat and prevent nitrogen deficiencies.
A lemon tree experiencing a manganese deficiency may develop mottled discolouration on its leaves. Yellow patches tend to appear between the largest leaf veins. The veins themselves remain bright green.
Manganese is a micronutrient found in some (but not all) store-bought fertilizers. If your lemon tree is prone to deficiencies, I recommend selecting a formula that contains manganese for general feedings. Manganese supplements can also be applied directly to foliage.
According to the University of Florida, zinc deficiency is one of the most widespread nutritional problems in citrus trees. Zinc deficiencies can happen alone or in combination with other nutritional deficiencies.
This deficiency can be identified by pale yellow leaves with vivid green primary veins. Serious deficiencies can also affect overall leaf size and shape.
Iron deficiencies also cause interveinal yellowing. Compared to a deficiency of manganese or zinc, however, both the large and small leaf veins tend to remain green while only small patches of regular leaf tissue turn yellow.
Lemon trees require more iron than many other plants. I recommend incorporating a chelated iron supplement into your feeding regimen. Some balanced fertilizers also contain chelated iron, so compare the labels of all products to prevent overuse.
Improper watering is a frequent culprit of yellow leaves on citrus trees. While both too much and too little water can cause yellow foliage, the former is more often to blame.
Lemon trees prefer deep but infrequent watering. The soil should be partially dry before adding more water.
You generally shouldn’t need to water an established lemon tree more than once per week except in times of extreme heat and drought. If you feel the need to water more often, you’re probably not irrigating deeply enough. Watering only the surface of the soil is ineffective because the moisture will evaporate before reaching the bulk of your tree’s root system.
Yellow leaves can also appear when conditions are overly dry. I usually encounter this problem in potted, indoor lemon trees that are kept near HVAC vents or other draft sources.
Insufficient Soil Drainage
Lemon trees grown in waterlogged soils are particularly prone to yellow foliage. It’s important to identify and address any drainage issues before planting lemon trees in the landscape.
Potted trees must be grown in containers with adequate drainage holes. Avoid keeping your lemon tree’s container in a collection tray. If you must use a saucer — e.g., to protect floors from water damage — I recommend elevating the pot slightly.
Lack of Sunlight
Lemon trees require about 8 hours of full sun per day for optimal growth. A tree that receives too little light may develop pale yellow leaves. This discolouration is the result of chlorophyll in the leaves breaking down from the absence of adequate sunlight.
Extreme Temperature Fluctuations
Extremely high or low temperatures can negatively impact lemon tree health and performance. Heat stress often presents as curling leaves that fade and turn yellow if conditions don’t improve. Cold damage is characterized by blotchy, discoloured leaves that may dieback completely in severe cases.
Little can be done to reverse temperature damage once it occurs. Instead, you should take steps to prevent heat or cold damage whenever possible. Provide supplemental shade and moisture when temperatures are high. If a cold snap is forecast in your area, cover or relocate lemon trees until conditions improve.
Yellow leaves that are isolated to select parts of your lemon tree and can’t be traced back to environmental factors may be a symptom of pest infestation. There are several pests that target lemon trees and their leaves.
Many such pests feed on lemon trees by piercing the leaves and sucking out the sap. This damage creates yellow or brown spots across the leaf surface.
Citrus mealybugs feed on lemon trees as well as many other popular garden plants. According to NC State University, one of the best ways to treat mild mealy bug infestations is by physically removing the pests using something like a strong hose spray. Insecticidal soaps labelled for use on mealy bugs are also effective.
Lemon trees are often the target of two-spotted and Yuma spider mites. In my experience, spider mites are best controlled via physical removal (e.g., spraying foliage with a powerful garden hose). Monthly applications of neem oil will provide reasonable control over future infestations.
Scale insects are interesting (though annoying) creatures that develop hard coverings to protect themselves as they feed on plant tissue. These pests somewhat resemble snails under a magnifying glass.
According to Clemson University, scale insects’ hard shells offer protection against many chemical insecticides. Horticultural oil and canola oil are the best alternative treatments.
Aphids are tiny pests that can cause incredible damage in large numbers. These pests reproduce very quickly, so even minor infestations should be taken seriously.
Routine applications of horticultural oil are effective against aphid infestations. I also recommend monitoring and controlling garden ant populations. Some ant species “farm” aphids for their excreted honeydew.
Note that aphids have many natural predators, the most famous being the ladybug (Hippodamia convergens). Chemical-based control methods used outdoors may also harm these beneficial insects.
In addition to treating a pest infestation with pesticides and horticultural oils, a great way to prevent them in the first place is to consider the planting scheme of neighbouring plants. Excellent companion plants for lemon trees include flowering plants such as geraniums and lupines and herbs such as lavender and rosemary.
A lemon tree can live for 50 years or more. However, individual leaves rarely last longer than a couple of years.
Older leaves will discolour and drop as their vitality comes to an end. This is a completely normal process. There’s no need to worry about ageing foliage turning yellow as long as the tree is otherwise healthy.
Removing Yellow Leaves On Lemon Trees
You don’t need to remove yellow leaves from your lemon tree. Old and damaged leaves will naturally shed on their own.
You can carefully pinch or prune off discoloured foliage as needed to improve your lemon tree’s appearance. This is more common for semi-ornamental lemon trees than for those grown exclusively for fruit production.
Verdict: Lemon Tree Leaves Turning Yellow
Yellow leaves aren’t a normal part of the lemon tree growth cycle. But I also can’t say this symptom is uncommon. Anyone growing lemons at home will likely encounter this problem at some point.
Most cases of yellow leaves are the result of malnutrition, improper watering, or environmental stressors. Common garden pests may also trigger discoloured foliage, though the symptoms tend to be a bit different than those caused by cultural factors.
Keep in mind that prompt diagnosis and treatment aren’t just key to improving your lemon tree’s appearance. Yellow leaves that go untreated can lead to other health problems, including issues with flower and fruit production.