My lime tree was getting curled leaves recently and I wanted to find out why. So, I did some research to find out more and how I can fix it. Here’s what I found.
Lime tree leaves curl most commonly when the tree doesn’t get enough water. Other reasons include excessive heat, a lack of nutrients, transplant shock, and aphids. Ideally, only water your tree when its soil is dry, provide compost and mulch, and spray aphids with water or neem oil. You can also use ladybugs.
So, while lime tree leaves curl for several reasons, how can you tell which issue is affecting your tree, and how can you fix it? Let’s take a closer look.
Under-watering is the most common cause of curled leaves on lime trees. When the tree is under-watered, the tree conserves moisture by curling its leaves. If it doesn’t get water soon, the leaves will die and be shed from the tree.
For best results, only water lime trees when the first 2-4 inches of soil gets dry. I check this by pushing my finger into the soil, under the tree’s canopy.
When watering, soak the soil down to at least 2 feet as over 90% of the tree’s roots are found within this depth.
The problem is many climates and regions have different temperatures, humidity, wind, soil, and other factors. This is why it’s helpful to water when your lime tree’s soil becomes dry.
Additionally, apply 2 inches of compost every 1-2 months and 4-12 inches of mulch every 3-6 months.
Compost not only provides plenty of nutrients (potentially replacing fertilizer) but also helps the richness of the soil. Each 1% increase in the soil’s organic matter holds 20,000 gallons more water per acre (source).
Mulch protects the soil from the elements and greatly improves water retention by reducing evaporation. Because of this, the soil life such as mycorrhizal fungi is protected and can continue to thrive (further benefiting your lime trees and other plants).
However, keep both compost and mulch at least 3 inches away from the tree’s trunk to prevent mold.
Overwatering is also a problem for lime trees, but it usually causes other issues such as root rot and yellow leaves. If your lime tree also has these issues, make sure to check out my recent post on why lime trees get yellow leaves.
2. Extreme Heat & Dryness
Extreme heat and dryness also cause lime tree leaves to dry and curl, which is compounded by a lack of water.
Lime trees are natively from the tropics, where temperatures are commonly between 35ºF to 90ºF. Like most tropical plants, lime trees get stressed if their temperature falls outside of this range.
To prevent leaf curl, keep your lime trees within 60ºF to 90ºF if possible.
While this can be difficult to do for outdoor lime trees, there are some ways to influence their temperature:
- Provide partial shade during the hottest part of the day (usually between 2 pm to 4 pm)
- Plant in a south-facing direction for maximum sunlight and warmth
- Insulate lime trees during times of frost
- Move potted lime trees indoors when temperatures are outside of 35ºF-100ºF
While it’s important to monitor the temperature of the tree that’s above the ground, it’s also incredibly helpful to check the tree’s temperature below the ground.
The primary way lime trees cool themselves is from their roots, since the roots transport moisture to the rest of the tree. If the tree is unable to send enough moisture to its leaves they’ll begin to curl and fall off.
This is why mulching is such an important practice. Not only will it improve water retention and help the beneficial life in the soil, but it protects the soil from baking in the hot sun.
So, when mulch cools the tree’s roots, it’s effectively cooling the entire tree.
3. 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
Certain nutrient deficiencies cause lime tree leaves to curl. The above table shows how you can identify the most common deficiencies for lime trees.
However, it’s not always obvious which nutrient is deficient in the soil. For this reason, applying a regular boost of a complete nutrient profile is recommended.
The Best Way To Fertilize Lime Trees
The best fertilizer for lime trees is either chemical fertilizer or compost. If you’re using fertilizer, aim for one with double the nitrogen to phosphorus and potassium (abbreviated as NPK). Citrus trees are heavy feeders and require more nitrogen than most other fruit trees.
For example, an NPK of 6-3-3 works nicely.
To see which compost and fertilizers I recommend for lime trees, see my recommended fertilizer page.
Alternatively, you can apply 2 inches of compost every 1-2 months. Compost has other benefits such as retaining soil moisture and promoting soil health.
This beneficial soil life, such as mycorrhizal fungi, provides the lime tree with more water in times of drought and helps prevent pests and diseases.
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
While nutrients are important, they cannot be absorbed by the plant properly if the soil pH is too acidic or alkaline.
Lime trees prefer a soil pH of 6.0-7.0
The reason why most plants prefer a slightly acidic soil pH is because this is the pH that dissolves the nutrient solids. Only then are they accessible to the plant’s finer roots.
The best ways to check your soil’s pH are with strips or a meter. I prefer using a pH meter since they’re easy to use and affordable. To see which pH meter I use and recommend, check out my recommended tools page.
If you find your lime tree’s soil pH is too acidic (below 6.0), apply alkaline amendments such as wood ash, biochar, or lime.
For soil that’s too alkaline (above 7.0), apply acidic amendments such as sand, peat moss, and coffee grounds.
4. Transplant Shock
If your lime tree was recently planted or repotted, and its leaves are starting to curl, 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 lime 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 plant’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the plant’s stem 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 plant 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
Aphids are small bugs that suck the sap from underneath the lime tree’s leaves. This loss of sugar and moisture causes the leaves to curl, discolor, and drop.
When aphids suck the plant’s sap, they deposit honeydew—which attracts ants. If left unchecked, aphids can damage the plant’s health and potentially stunt or kill the tree.
Aphids come in multiple colors and can appear as white, yellow, or black specs, usually 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.
The best ways to get rid of aphids and mites on lime trees are:
- Spraying with water
- Spraying with neem oil
- Releasing ladybugs
Each of these solutions has a different way of managing aphids. Water knocks them off the leaves and kills them, neem oil traps them, and ladybugs eat them (ladybugs are a natural predator of aphids and mites).
Most often, a jet of water is enough to knock them off and kill them, but neem oil and releasing ladybugs are good second options.
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. Keep in mind that too strong of a blast can damage the leaves.
If your lime tree’s leaves have yellow or brown spots, or you believe your lime tree has a disease, refer to this citrus tree disease guide by the University of California.