I’ve had to troubleshoot several issues with my citrus trees (especially my Meyer lemon and Kaffir lime), but one of the most common issues that I’ve seen is when their leaves curl. While I had an idea of what could be causing it, I wanted to dive in deeper. So, I did some research and testing to find out more. Here’s what I found.
Generally, citrus leaves curl when the tree doesn’t get enough water. When this happens, the leaves curl to conserve moisture. Leaf curl can also be caused by extreme weather and some pests and diseases. However, under-watering is the most common cause, so water as needed and use mulch and compost.
So, while under-watering is the most common reason why citrus leaves curl, how can we be sure what the exact issue is, and how can we fix it?
Under-watering is the most likely cause of citrus tree leaf curl. When under-watered, the leaves dry out and begin to curl as a result. The best way to make sure your citrus tree gets enough water is to only water when the first 2-4 inches of soil gets dry. This is typically every 2 weeks, depending on the weather.
Leaf curl isn’t only an issue for citrus trees. It commonly occurs for most plants, especially other fruiting trees. Once the tree is under-watered, if not watered soon, it will shed its curled leaves and conserve the little water it has left to ensure survival.
While it can be tricky to know when and how much to water your citrus tree, these tips have helped me quite a bit:
- Only water when the first 2-4 inches of soil gets dry
- Provide 1-2 inches of mulch to help the soil retain water
- Add compost every 1-2 months for extra nutrients and to improve the richness of the soil
All of the above tips helped tremendously, and not just for my citrus trees, but also for my tomato, cucumber, and other plants in the garden.
By only watering when the first 2-4 inches of soil gets dry, not only are you checking that you’re not under-watering your citrus tree but not overwatering it as well (more on this below).
Simply push a finger in the first 2-4 inches of soil to tell how dry or wet the soil is. Bone dry definitely needs more water and sopping wet needs much less (or more drainage). The goal for the soil should be the wetness of a wrung-out sponge.
Mulching is also a significant part of managing the water content in the soil. Soil isn’t meant to be bare, and when it is, it’s vulnerable to the sun, wind, and rain and can be easily eroded. By mulching, you’re not only protecting the soil from the elements, but you’re reducing evaporation—locking in essential moisture in the soil. Naturally, this reduces how much and how often you’ll need to water your citrus trees. Some good mulches for citrus trees are leaves, bark, or pine needles.
Composting is equally as important as mulching as it not only improves the nutrient profile of the soil (many times replacing chemical fertilizers), but it increases the richness of the soil. With each 1% increase in the soil’s organic matter, the soil can help hold 20,000 gallons more water per acre. That’s a lot of water saved (and much less strain on your water bill).
On the other hand, overwatering can also cause issues with citrus tree leaves. However, most commonly the leaves don’t curl, but instead—drop. Overwatering can also lead to other issues such as yellow leaves.
If you’d like more information about yellow leaves on citrus trees and what to do about it, check out my recent post.
Another common reason why citrus trees get leaf curl is because of extreme weather, or swings in temperature. Citrus trees grow in temperatures from 35ºF-100ºF and can get stressed if their temperature falls outside of this range. To prevent leaf curl, keep citrus trees within 60ºF-80ºF if possible.
While citrus trees can tolerate temperatures as low as 35ºF and as high as 100ºF, like most plants, they prefer less extreme temperatures. This makes their sweet spot about 60ºF-80ºF. However, this range is not always possible to maintain (unless you’re growing potted citrus trees indoors).
Still, there are a few things you can do to influence the temperature a bit, even if your citrus trees are outdoors.
Preventing Curling Leaves in Hot Weather
If your weather consistently gets above 90ºF-100ºF, consider shading your citrus trees during the hottest part of the day. This is generally around 2-4pm. Even by providing a short break from the sun, your citrus trees will be able to cool off effectively and reduce the chance of leaf curl.
Smaller citrus trees are more vulnerable to the heat since their roots aren’t as deep as larger trees. This is because deeper roots are better protected from the heat and can access more water. The roots then send moisture to the rest of the tree, keeping it cool.
You can shade smaller citrus trees with a patio umbrella or with other, taller trees. For best results, plant the taller tree on the west side of the citrus tree to allow for the break from the afternoon sun.
On the other hand, larger citrus trees (above 10-15 feet tall) typically don’t require shade but will thrive if their soil and roots are protected from the hot sun and wind. For this reason, it’s highly recommended to mulch your citrus trees (including the smaller ones). As a bonus, you can provide drip irrigation to reduce evaporation and keep more water in the ground, cooling the tree further.
Preventing Curling Leaves in Cold Weather
Since citrus trees are native to the tropics, they tend to favor hot weather over cold. Still, many regions that grow citrus trees can experience frost occasionally.
If your area gets frost every now and then, there are a few things you can do to help your citrus tree survive and limit its leaves from curling and falling off:
- Plant citrus trees facing south for maximum sunlight and warmth (and avoid planting in a northern-facing direction)
- Plant along a southern-facing wall to provide even more light and warmth as it reflects off the wall, even into the night
- Insulate citrus trees with sheets, cardboard, or another insulating material
- Protect against wind chill by using windbreaks such as other trees, walls, or another structure
- Keep indoor citrus trees next to a southern-facing window
- Avoid placing indoor citrus trees next to central heater vents (I have personal experience with this)
So, if you check the weather and you see frost coming to your area, consider using the above tips to protect your citrus trees and keep their leaves from curling and falling off.
Make sure to transition your tree to a new temperature (including indoors) slowly. A big swing in temperature (15ºF or more) can stress the tree and curl the leaves even more. If possible, transition the tree gradually over two weeks. Of course, an exception to this is if there’s a last-minute frost.
Pests and Disease
While it’s not as likely as other causes, pests and disease can lead to leaf curl and drop on citrus trees. The most common are aphids and spider mites. To get rid of these pests, you can spray them with a jet of water, use neem oil, or use natural predators such as ladybugs.
Generally, pests such as aphids are more likely to cause citrus tree leaf curl than diseases. This is because aphids and other pests suck the sap from the leaves, taking their moisture and making them curl. On the other hand, diseases usually show as spots on leaves or issues with the bark.
Aphids come in multiple colors and can appear as white, yellow, or black specs, usually underneath the leaves.
Aphids can really be pests, but they’re not too hard to get rid of. The most effective ways to get rid of aphids on citrus trees are:
- Spraying with water
- Spraying with neem oil
- Releasing ladybugs
When my Kaffir lime tree had aphids recently, I first 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 kick them off of the leaves.
All I did was remove the nozzle from the hose and fit my thumb over the opening to create a stronger blast of water. It was strong enough to remove the aphids, but not strong enough to damage the leaves. To this day, the aphids have yet to return.
Even though spraying with water worked to remove the aphids, I asked my local nursery for other ways to successfully get rid of them in the future. In addition to water, they suggested neem oil and ladybugs. Like most nurseries, they sold both neem oil and ladybugs, so they’re typically not hard to come by.
Neem oil works by trapping the aphids and rendering them unable to move, while ladybugs are a natural predator to aphids.
While not as common as aphids, spider mites can also be removed with water or neem oil.
I’m not a big fan of using chemicals, including insecticides, but I won’t stop you from using them. However, I would suggest first trying natural methods such as neem oil or ladybugs. Again, just a spray of water was enough to get rid of aphids on my lime tree.
If you’d like more information about getting rid of aphids, feel free to check out my latest post: Get Rid of Aphids on Fruit Trees: The Top 3 Ways.
As mentioned, citrus tree disease usually shows as spots, not leaf curl. Some diseases, such as root rot (a fungal disease) can cause leaves to curl, yellow, and drop, but this is usually directly caused by overwatering. If your citrus tree soil is smelling swampy, and the water is stagnant, it likely has root rot and needs to be repotted with fresh, well-draining soil.
If you believe your citrus tree has a disease, or its leaves have yellow or brown spots, consider referring to this citrus tree disease guide by the University of California.
More Tips To Prevent Citrus Tree Leaf Curl
- A lack of nutrients isn’t likely to cause leaf curl, but it can cause similar issues such as yellow and dropping leaves. Aim for a fertilizer with an NPK ratio of 2:1:1 (twice the nitrogen to phosphorus and potassium), such as Down to Earth’s 6-3-3 Citrus Mix. For more about fertilizers, check out my recommended citrus fertilizer page. Alternatively, you can use compost or make your own citrus tree fertilizer at home.
- For best results, water the soil and around the drip line of the tree. While misting curled leaves can introduce moisture directly and help cool the leaves, the tree more effectively cools itself through its roots. Watering the leaves directly can also splash fungus or other diseases from leaf to leaf.
- Check the soil’s moisture and temperature every few days (or every 1-2 weeks if mulching and composting). You can use a moisture meter to help with this (it also reads the pH of the soil). To see which moisture/pH meter I recommend and use, check out my recommended tools page.
- Use self-watering pots to help prevent leaf curl for indoor citrus trees. This should reduce how quickly the soil drys out. However, keep an eye on the soil as I’ve found that it can get moldy faster and more prone to root rot.
- Good soil is key to aid in proper drainage, nutrients, and root growth. For best results, use loose, rich soil from a reputable brand such as Espoma’s potting soil found on Amazon. Alternatively, you can make your own citrus tree potting soil at home.
- Mulching and composting are key not only to protect the soil and regulate the tree’s temperature but to retain the nutrients in the soil. This is because mulching and composting protect the bacterial and fungal layer (mycelium) in the soil which provides the tree with many nutrients the roots cannot reach. Healthy soil means a healthy tree!