My potted Meyer lemon tree sometimes gets curled leaves, which is a problem because they soon drop from the tree. I’ve heard mixed reasons as to why this happens, so I did some research to find out more. Here’s what I found.
Lemon trees get curled leaves from improper watering, nutrients, climate, and pests such as aphids. However, the two most common causes are a lack of water and aphids. Ideally, only water your lemon tree when its soil is dry, and check the underside of the leaves for any signs of aphids.
So, while lemon tree leaves curl for several reasons, how can we tell which issue is affecting your tree and how can we fix it? Let’s take a closer look.
1. Under-Watering
You can tell if your lemon tree is under-watered if their leaves quickly curl, droop, brown, and drop. However, if you catch it fast enough (such as when the leaves begin to curl), you can save the leaves. On the other hand, if you don’t catch it in time, the leaves will begin to brown and drop from the tree.
Fortunately, there are some tips you can use to ensure your lemon tree gets enough water.
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. The goal is to have soil moisture similar to a wrung-out sponge.
By watering in this way, you’re avoiding both under and over-watering. Plus, by watering less often and in deeper amounts, you’re encouraging your lemon tree to grow deeper roots—helping it become more water independent.
Since over 90% of the lemon tree’s roots grow within the first 2 feet of soil (source), it’s best to water to this depth.
Additionally, compost and mulch are key to a thriving and independent lemon tree.
Compost provides valuable nutrients, feeds beneficial soil life, and increases the soil’s richness. For example, every 1% increase in the soil’s richness leads to an extra 20,000 gallons of water held per acre (source).
On the other hand, mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. Since lemon trees evolved in forests as an understory species, they do best with some afternoon shade and a thick layer of mulch (in the forest, they would have plenty of mulch in the form of fallen branches and leaves).
Mulch is also key for beneficial soil life such as mycorrhizal fungi to thrive. This beneficial fungi drastically assist trees and other plants by retaining soil moisture, warning the tree of nearby pests and diseases, and trading nutrients in exchange for sugar from the tree’s roots.
Mycorrhizal fungi promote many aspects of plant life, in particular improved nutrition, better growth, stress tolerance, and disease resistance.
Department of Biology, University of Fribourg, Switzerland
Are you on board yet?
Good, here’s a quick summary of the optimal watering experience for your lemon tree:
- Water only when the soil is dry
- Provide 2 inches of compost every 1-2 months
- Apply 4-12 inches of mulch every 3-6 months
While this might seem like a lot at first, following these best gardening practices is key for lemon trees to survive and thrive. This is especially true if you’re not able to tend to the tree every day (let’s face it—it’d be nice to not have to baby our garden all the time).
By doing the above practices, not only are you preventing under and over-watering, but your lemon tree’s deeper roots help it access deeper water and cool itself in hot and dry climates.
2. Extreme Heat
Speaking of hot climates, lemon trees that are exposed to excessive heat and dryness develop issues similar to under-watering, including leaves curling, drooping, browning, and dropping.
Lemon trees are native to the tropics, so they prefer a warm and humid environment. Ideally, this includes USDA hardiness zones 9 to 11.
There are even some cases where lemon trees can be grown in cooler climates (such as if you use a greenhouse or move potted lemon trees indoors during the winter).
However, what do you do if you’re in a dry climate, or if it gets too hot (over 90ºF)?
Lemon trees suffer the most if they’re:
- Planted in open fields without any shade
- Grown only with other lemon trees (monoculture)
- Fertilized with potent chemical fertilizers
- Grown in dry climates such as Arizona and California
Before we get into the solutions, it’s helpful to know just how lemon trees keep themselves cool.
Lemon trees cool themselves by sending moisture from their roots to their leaves, and through a process called transpiration.
Similar to how humans exhale moisture when we breathe, plants do the same. This is why it’s so humid in forests and dense canopies. Generally, the top part of a plant’s leaf is like a solar panel (for photosynthesis), while the bottom exhales moisture.
The problem arises when it gets too hot and dry and the plant’s roots and transpiration can effectively keep up. When this happens, the plant’s leaves begin to droop, curl, brown, and drop.
Side note: if you’d like to learn more about transpiration, and other cool behaviors of plants, I highly recommend the book The Hidden Life of Trees by professional German forester Peter Wohlleben.
Fortunately, there are some fairly simple ways to counter hot and dry conditions.
- Provide some afternoon shade for lemon trees. You can use umbrellas, patios, or shade sails to help shade it. Another great option is to use overstory plants such as acacia and even pine. Acacia is also a nitrogen-fixing plant, so it’s a great companion plant to have alongside your lemon tree.
- Cover crops are another companion plant for lemon trees that shade the soil and act like a sponge—absorbing vast amounts of water into the soil. As long as the tree’s roots have enough moisture, the likelihood of it getting curled leaves from dry air is nearly zero. And like acacia, cover crops are nitrogen-fixing.
- Avoid using fast-release chemical fertilizers. While chemical fertilizers have nutrients in quantity, they often lack nutrients in quality. Because of this, many gardeners are finding that compost can replace fertilizer in the long run.
- Apply compost and mulch to provide the most optimal watering for your lemon tree. Keep these materials at least 3 inches from your lemon tree’s trunk as they can introduce mold if they’re wet for long periods.
So, even if you live in a hot and dry climate, by following the above tips, your lemon tree will stand a chance and make it to maturity. And once it’s mature, you won’t need to pamper it nearly as much!
3. Improper Nutrients
Excess Nutrients
Excess nutrients (caused by over-fertilizing) chemically burn the lemon tree’s roots. This stresses the tree, which results in curled, yellow, and dropping leaves as well as stunted tree 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 |
On the other hand, a lack of nutrients also causes the lemon tree stress, leading to similar conditions such as leaves drooping, curling, 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.
And since lemon trees are tropical plants (often growing in sandy soils) nutrient leaching is fairly common. However, an easy way to prevent leaching is by using mulch to retain the nutrients in the soil for longer.
Aside from mulching, most of these issues can be resolved by properly fertilizing lemon trees.
The Best Way To Fertilize Lemon Trees
The two main ways to fertilize your lemon tree are with fertilizer or compost. If you choose a store-bought fertilizer, aim for an NPK (nitrogen, phosphorus, and potassium) with double the nitrogen to phosphorus and potassium. For example, use a 6-3-3 NPK.
Keep in mind, that while chemical fertilizers might be sufficient over the short term, over the long term they often short-circuit the nutrient exchange between the tree and its beneficial soil life. This leads to dry and dead soil (AKA dirt) and overall decreased plant health.
On the other hand, compost provides more than sufficient nutrients, increases water retention, and promotes healthy soils. Choose fresh and quality compost as its beneficial soil life and bacteria will still be alive.
Either route you take—you can see my recommendations for both compost and fertilizer on my recommend fertilizer page.
Soil pH
Lemon trees need a soil pH of 6.0 to 7.0 (source).
While nutrients are important, they’re near useless if the soil does not have a proper pH.
This is because a slightly acidic pH dissolves the nutrient solids in the soil and makes them accessible to the plant’s finer roots.
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 dormant during the cold or too stressed in wet soils.
4. Transplant Shock
If your lemon tree was recently planted or repotted, and its leaves are starting to curl, it’s likely due to transplant shock. Transplant shock occurs when the plant is exposed to a new environment and has to establish a new root system. Avoid transplanting unless necessary as it can take up to 1 year for recovery.
Like many plants, lemon trees are vulnerable to transplant shock, which can take up to a year for them to recover from. 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 plant’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the plant’s trunk and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the plant in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the trunk or stem as before
- Apply 2 inches of compost and 4 inches of mulch to the top of the soil
- Water generously and add more soil as needed
Keep in mind that potted lemon trees need to be repotted into a larger container every 3-5 years as their roots will outgrow it. When repotting, use fresh potting soil to avoid collapsed soil and root rot.
5. Aphids
Occasionally, pests lead to leaf curl and drop on lemon trees. The most common are aphids and spider mites. To get rid of these pests, spray them with a jet of water or neem oil, or encourage aphid predators such as ladybugs.
Aphids come in multiple colors and can appear as white, yellow, or black specs, usually underneath the leaves.
Generally, aphids are more likely to cause lemon tree leaf curl than other pests and diseases. This is because aphids suck the sap from the leaves, taking their moisture and making them curl.
Aphids can truly be pests, but they’re not too hard to remove.
Here are the simplest and most effective ways to get rid of aphids:
- Spray water
- Spray neem oil
- Release ladybugs
When my Kaffir lime tree recently had aphids, I wasn’t sure how to get rid of them. After some research and testing, I found that a simple jet of water from a hose was enough to knock them off of the leaves. This sounds too good to be true, but it really worked!
All I did was remove the nozzle from the hose and fit my thumb over the opening to create a stronger jet of water. The key here is to have the water strong enough to remove the aphids, but not strong enough to damage the leaves.
The aphids haven’t returned since.
While not as common as aphids, spider mites also cause curling leaves and can be removed with the same methods (water, neem oil, and ladybugs).
