Limes – Couch to Homestead

We have a few lime trees including a Persian and Kaffir lime tree, and there was a time when their leaves were curling. I thought this issue might be affecting their growth and fruiting, so I did some research to find out more. Here's what I found that can fix curling leaves on lime trees. In general, lime leaves curl when the tree doesn’t get enough water. Essentially, the leaves curl to conserve moisture. To fix curled leaves, water the tree when its soil gets dry and provide it with mulch and compost. Leaf curl on lime trees can also sometimes be caused by extreme weather and some pests and diseases. 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 further look. Under-Watering Under-watering is the most common cause of curling leaves on lime trees. When the tree is under-watered, the tree conserves moisture and begins to shed its leaves. For best results, only water lime tree when the first 2-4 inches of soil gets dry. This is typically every 1-2 weeks, depending on the weather. The bad news is that it's easy to under-water your lime tree. The good news is that it's easy to fix. If you've ever juiced limes that had little to no juice in them, you know it can be frustrating. Like other citrus trees, lime trees like a lot of water. This makes sense since they typically grow in hot climates and require plenty of water to make their fruits, well, juicy. So, watering properly not only helps hydrate the lime trees and their leaves but also gives you plenty of plump juicy limes! The problem is that many climates and regions have different temperatures, humidity, wind, soil, and other factors. Because of this, there's no one rule on how to water your lime tree—you have to water based on your lime tree's environment. Fortunately, you can find out how much to water your lime tree by simply testing the soil with a finger. Push a finger 2-4 inches into the soil under the drip line of your lime tree. If the soil is bone dry, your tree needs more water. If the soil is sopping wet 2+ hours after watering, the tree needs less water (and more drainage). The goal is for the soil to have the same moisture as a wrung-out sponge. If you're watering your lime tree more than once a week, its soil is likely drying out too fast. This is usually caused by too much drainage or environmental factors such as the sun and wind. In this case, mulching and composting are highly recommended for just about every lime tree (and most other plants in your garden). Composting not only provides plenty of nutrients (potentially replacing fertilizer) but also helps the richness of the soil. It's reported that with each 1% increase in the soil’s organic matter, the soil can help hold 20,000 gallons more water per acre. On the other hand, mulching protects the soil from the elements and greatly improves water retention by reducing evaporation. Because of this, the soil life is also protected and can continue to thrive (further benefiting your lime trees). To compost and mulch your lime trees, provide 1-2 inches of compost every 1-2 months, and 1-2 inches of mulch every 3-6 months around the drip line of the tree. Make sure to keep both materials at least three 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 yellowing leaves, make sure to check out my recent post on why lime trees get yellow leaves. Extreme Weather Extreme weather, or swings in temperature, can also cause lime tree leaves to curl. Lime trees typically grow in temperatures from 35ºF-100ºF and can get stressed if their temperature falls outside of this range. To prevent leaf curl, keep your lime trees within 60ºF-80ºF if possible. When temperatures become too extreme, or there's a dramatic swing in weather, lime trees can become stressed and curl their leaves as a result. Leaves can also curl if temperatures get too hot and dry out the leaves. To help prevent this, aim to keep your lime tree's temperature between 60ºF-80ºF if possible. While this can be difficult to do for lime trees that are outdoors, there are some ways to influence their temperature: Provide shade during the hottest part of the day (usually between 2pm-4pm)Plant in a south-facing direction for maximum sunlight and warmthInsulate lime trees during times of frostMove 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 ground. Meaning the temperature of the soil, and therefore—the tree's roots. 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, by cooling the roots, mulching effectively cools the entire tree. You can also use drip irrigation to reduce water evaporation and make sure the soil gets properly saturated with water. Pests and Disease Even though it’s not as likely as other causes, pests and diseases can lead to leaf curl and drop on lime 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, aphids are more likely to cause lime tree leaf curl than other pests and diseases. This is because aphids suck the sap from the leaves, taking their moisture which makes them curl. 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 lime trees are: Spraying with waterSpraying with neem oilReleasing 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. 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. While not as common as aphids, spider mites can also be removed with water or neem oil. On the other hand, you can usually identify diseases from any spots on the leaves or issues with the bark. If you believe your lime 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 Lime Tree Leaf Curl Use self-watering pots to help prevent leaf curl for indoor lime 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 lime tree potting soil at home.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.For best results, water the soil around the drip line of the tree. While misting the curled leaves can introduce moisture directly and help cool them, the tree more effectively cools itself through its roots. Watering the leaves directly can also splash fungus or other diseases from leaf to leaf.