We have a large lemon tree in our backyard and every now and then, the tree starts dropping more leaves than usual. While it’s not dropping a lot of leaves, we were concerned it was getting worse and wanted to find out more. Here’s what we found.
Lemon trees drop leaves from improper watering, climate, nutrients, as well as transplant shock, pests, and diseases. However, the most common issues are watering and climate. To prevent leaves from dropping, only water lemon trees when the first 2-4 inches of soil gets dry, and avoid temperatures below 32ºF.
So, while lemon trees drop their leaves for several reasons, how do we know which issue is causing it, and what are some steps we can take to fix it? Let’s take a closer look.
Table of Contents
Do Lemon Trees Normally Lose Their Leaves?
Since lemon trees are evergreen trees, they normally do not shed all of their leaves in the winter like deciduous trees (apple, cherry, etc).
It’s normal for lemon trees to lose around 10% of their leaves at any given time. This is a natural process of the leaves getting older and making room for younger leaves.
However, if a lemon tree has lost more than 10% of its leaves, it’s likely stressed from something.
1. Under-Watering
When lemon trees are lacking water, they’re unable to keep themselves hydrated and cool. As a result, the tree’s leaves commonly curl, brown, and drop.
Fortunately, you can catch an under-watered lemon tree fairly early if you spot the majority of its leaves curling. This is because its leaves curl as a last-ditch effort to retain moisture.
If you can water the tree before the leaves turn brown, the leaves should make a full recovery.
However, if many of the leaves are already brown or dropped—don’t worry! The tree can still recover (my lemon tree lost most of its leaves at one point, but it recovered the following season).
The best way to water lemon trees is to only water when the first 2-4 inches of soil is dry. A good way to check this is by pushing a finger into the soil, under the tree’s canopy. Additionally, provide compost and mulch.
Make sure to water down to 2 feet deep as more than 90% of the lemon tree’s roots are found at this depth.
By using this method, you’re not only preventing under-watering but over-watering too (more on this later).
However, watering is only part of the picture. There are times when your lemon tree’s soil dries so fast that you need to water it multiple times a day.
So, how do you improve the water-holding capacity of the soil and water your lemon tree less?
Compost not only provides valuable nutrients but improves the soil’s richness. Every 1% increase in the soil’s richness and organic matter leads to it holding an additional 20,000 gallons of water per acre (source).
On the other hand, mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. Lemon trees evolved in forests as midstory plants, so they prefer some afternoon shade and copious amounts of mulch (in the forest, this was from fallen branches and leaves).
For best results, apply 2 inches of compost and 4-12 inches of mulch. Reapply compost every 1-2 months and mulch every 3-6 months. Keep both materials at least 3 inches from your lemon tree’s trunk to prevent mold buildup.
However, if your lemon tree is over-watered, then definitely hold off on the mulch for now as it will make the issue worse.
2. Over-Watering
Symptoms of over-watered lemon trees include leaves yellowing, browning, and dropping. These conditions are caused by stress from waterlogged soil.
If the soil is sopping wet for too long, it will develop root rot (as quickly as a few days).
For example, I could tell my potted Kaffir lime tree had root rot at one point because its leaves were yellowing and dropping, and its soil smelled like a swamp. After repotting the tree with fresh potting soil, its root rot disappeared and the tree grew new green leaves.
So, even if you’re watering your lemon tree properly, it still can become over-watered if the soil isn’t draining well.
Poor Drainage
The ideal soil for lemon trees is sandy loam. This means the majority of the soil is sand (52% or more), but enough silt, and clay (less than 20%), to hold nutrients and water.
| Soil Type | Pros | Cons |
|---|---|---|
| Sand | Good drainage | Doesn’t hold nutrients well |
| Silt | Holds nutrients well | Poor drainage |
| Clay | Holds the most nutrients | Even worse drainage than silt |
You can tell if your lemon tree has sufficient drainage by digging a nearby hole 1-foot deep and wide, and filling it with water. If the hole drains slower than 2 inches per hour, it has poor drainage.
Make sure to dig the hole outside of the lemon tree’s canopy or drip-line to avoid damaging the tree’s shallow roots.
For planted lemon trees that are mature, amend the soil by applying 2 inches of compost every 1-2 months. The compost will work its way into the soil over time and promote better drainage.
For planted lemon trees that are young, you can do the same or transplant them to an area with better soil (more on transplanting later).
If there are no areas with better soil, consider planting the tree in a mound of soil or in a raised bed to have gravity assist the drainage. See my other post for more information on planting in mounds and working with heavy clay soil.
For potted lemon trees with poor drainage or collapsed soil, the best method is to repot them with fresh potting soil. This is because compared to mature, planted trees, transplant shock is far less likely and severe for potted plants.
Keep in mind to repot lemon trees into larger pots every 3-5 years to allow for proper root space and aeration. Lemon trees planted in the ground typically don’t have these issues as their roots aren’t bound and beneficial insects such as earthworms naturally aerate their roots.
Avoid applying mulch on waterlogged soil as it traps moisture and prevents evaporation. However, once your lemon tree’s soil is well-draining, proceed with applying the 4-12 inches of mulch.
3. Extreme Weather
Lemon trees are natively from the tropics, so they prefer a warm climate, plenty of rain, and humidity. Because of this, they grow best in USDA hardiness zones 9 to 11 (source).
Ideally, keep lemon trees in temperatures between 32ºF to 90ºF.
While lemon trees can tolerate some exposure outside of these temperatures, prolonged periods can begin to brown and drop leaves and kill the tree.
Tips for Hot and Dry Weather
- Apply compost and mulch. Seriously, these two practices are gold in retaining water and promoting water independence for your lemon tree!
- Provide partial shade from the afternoon (west) sun. You can use umbrellas, shade sails, or other trees. Taller trees such as acacia work nicely (as a bonus, acacia are nitrogen-fixers).
- Water when the soil is dry. In extremely hot and dry weather, you may need to check your lemon tree’s soil more often.
Tips for Cold Weather
- Move potted lemon trees indoors during frost. However, avoid placing it near the central heat as the dry air will quickly drop leaves (I learned this the hard way with my potted Meyer lemon tree). Move the tree into a cooler room to avoid the lemon tree dying.
- Apply 1-2 feet of mulch to the base of planted lemon trees to help insulate them
- Cover the lemon tree’s canopy with a sheet to reduce the effects of wind chill and ice buildup
- Plant in a south-facing direction for maximum sunlight and warmth (north-facing if you’re in the southern hemisphere).
In general, it is recommended citrus trees be protected when the temperatures is expected to go below 27 degrees for an extended period.
Dr. William Johnson, Extension Horticulturist, Galveston County Texas AgriLife Extension Service
4. Improper Nutrients
Excess Nutrients
Excess nutrients (caused by over-fertilizing) chemically burn the lemon tree’s roots. This stresses the tree, which results in discolored and dropping leaves as well as stunted growth. Normally, fast-release chemical fertilizers are the cause of over-fertilization as compost isn’t potent enough.
Lack of Nutrients
| Nutrient Deficiency | Leaf Symptom |
|---|---|
| Nitrogen | Entire leaf is pale or yellow |
| Iron | Dark green veins, rest of the leaf is yellowing |
| Zinc | Yellow blotches |
| Manganese | Broadly pale leaves, foliage color looks mottled or smeared |
A lack of nutrients also causes the tree stress, leading to similar conditions such as discolored leaves and stunted growth.
Insufficient nutrients are commonly caused by poor soils, leaching, and other conditions such as improper pH.
Nutrient leaching is when the nutrients seep too far down into the soil, out of reach of the plant’s roots (beyond about 2-3 feet). This normally occurs when soils have too much drainage or are over-watered. For example, sandy soils are notorious for their leaching.
Fortunately, these issues can be resolved by properly fertilizing lemon trees.
How to Properly Fertilize Lemon Trees
The two main methods to provide lemon trees with nutrients are:
- Compost
- Chemical Fertilizers
However, many gardeners recently have been switching from fertilizer to compost. And they have a good reason.
While chemical fertilizers have nutrients in quantity, they typically lack nutrients in quality. For example, the nutrients found in synthetic fertilizers aren’t as bioavailable or absorbable as the nutrients in compost. Additionally, fertilizers often leave behind a crust on the top of the soil, drying it out.
Lemon trees prefer soil that’s full of beneficial soil life such as earthworms and mycorrhizal fungi (mycelium). This beneficial fungi grows naturally in the soil of forests and provides many advantages such as greatly improved water retention, accessible nutrients, and disease resistance.
Mycorrhizal fungi promote many aspects of plant life, in particularimproved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
This boost in nutrients comes from mycorrhizal fungi trading nutrients found deeper in the soil (out of reach of the lemon tree’s roots) in exchange for carbon (sugar) from the tree’s photosynthesis.
This is why mulch is so important for lemon trees (and other fruit trees)—it simulates a fallen forest, providing nutrients and the medium for mycorrhizal fungi and mycelium to thrive!
Apply 2 inches of compost every 1-2 months and 4-12 inches of mulch to provide the ideal nutrients and conditions for lemon trees to thrive. Benefits include dramatically increased water retention, nutrients, and disease resistance.
Not only are compost and mulch simply magic for lemon trees, these materials regulate the soil’s temperature, helping lemon trees thrive in slightly warmer or colder weather.
However, if you’d still like to use fertilizer, select one with double the nitrogen to phosphorus and potassium (NPK) as lemon trees are heavy feeders. For example, a 6-3-3 NPK works nicely. To see which fertilizers I recommend, check out my recommended fertilizer page.
But nitrogen isn’t the only nutrient to provide lemon trees! Nutrients such as phosphorus are important for fruiting and other plant functions. However, most composts and fertilizers will have sufficient primary and secondary nutrients.
Imbalanced Soil pH
While nutrients are essential, lemon trees also need a slightly acidic soil pH of 6.0 to 7.0 (source). This is because a slightly acidic pH is required to dissolve the solid nutrients in the soil.
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
Without a proper pH, lemon trees develop growing issues and conditions such as drooping, yellowing, and dropping leaves.
Two good ways to check your soil’s pH are either by usinga 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 myrecommended tools page.
If you find that your lemon tree’s soil is too alkaline (above 7.0) you can add acidic amendments such ascoffee 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 soilsare not good at promoting nutrient uptake as the lemon tree will either be dormant during the cold or too stressed in wet soils.
5. Transplant Shock
If your lemon tree was recently planted or repotted, and its leaves are dropping, it’s likely due to transplant shock. Transplant shock occurs when a plant is exposed to a new environment and has to establish a new root system.
Avoid transplanting lemon trees unless necessary as it can take up to 1 year for recovery.
To help avoid transplant shock, I like to plant with the following steps in mind:
- Have the new ground (or pot) prepared
- Remove as much of the tree’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the tree’s trunk and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the tree in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the trunk as before
- Apply 2 inches of compost and 4-12 inches of mulch to the top of the soil
- Water generously and add more soil as needed
6. Pests
Aphids
Aphidsare small bugs thatsuck the sap from underneath the lemon tree’s leaves.This loss of sugar and moisture causes the leaves to curl, discolor, and drop. They also deposit honeydew, which attracts ants. If left unchecked, aphids can damage the lemon tree’s health and potentially stunt or kill it.
These bugs come in multiple colors including white, yellow, or black, and usually hide underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the trees, they can compromise its health and therefore reduce fruit size.
The best ways to get rid of aphids on lemon trees are by spraying the infected leaves withwater or neem oil, or by releasing ladybugs(a natural predator of aphids). Most often, a jet of water is enough to get rid of them, but neem oil is a good second option.
For example, when my potted Kaffir lime tree had aphids, I found that a jet of water was enough 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. Keep in mind that too strong of a blast will damage the leaves.
Citrus Leaf Miners
We recently purchased a young lemon tree from our local nursery, and it soon started to get leaves that curled and dropped. The leaves also had some bumps and white trails. We sent it off to be analyzed and they told us it was leaf miners.
Recommended: How to Fix White Leaves on Citrus Trees
Leaf miners are small white moths that lay larvae to burrow inside of the leaves of citrus trees, causing them to curl and drop. This pest is fairly common in most of California along with Florida and Mexico.
The good news is that leaf minors don’t cause much damage and are only a concern for young lemon trees. Once the leaves harden off and mature, the leaf miners won’t be able to penetrate them.
The best way to prevent and manage leaf miners is to encourage natural predators such as beneficial wasps (the non-stinging kind).
You can do this by planting companion plants such as:
- Fennel
- Caraway
- Dill
- Yarrow
- Parsley
- Tansy
- Zinnia
- Coriander (cilantro)
- Queen Anne’s lace
- Sweet alyssum
Avoid using sprays as they’re not that effective and will cause more damage (instead promoting whiteflies, scale insects, and other citrus pests).
Available insecticides for backyard trees are not very effective and many products leave residues that kill natural enemies, compounding problems.
University of California Agriculture & Natural Resources
Also, avoid pruning leaves infected with leaf miners as the leaves are still functional and feeding the lemon tree via photosynthesis. Pruning can cause more damage in this case.
Feel free to prune leaves that are brown as they’re no longer assisting with photosynthesis, but it’s not necessary.
7. Diseases
Root Rot
Root rot, also called Phytophthora Root & Crown Rot, is a root fungus that causes leaves, blossoms, and fruit to droop, yellow, brown, and drop.
This disease typically occurs in soil with poor drainage. To prevent and treat root rot, promote well-draining soils and transplant the lemon tree with fresh soil if necessary.
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
As mentioned earlier, my potted Kaffir lime tree had root rot and made a full recovery after repotting it with fresh potting soil. So, if your lemon tree’s soil is sopping wet days after watering it, and it’s starting to smell like a swamp, repotting will likely fix it.
After doing this research, I applied compost and mulch to the base of our lemon tree and it started to recover! No more dropping leaves (besides the normal couple here and there)!
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