My parents have an orange tree that’s declining in health and they noticed it started to get curled leaves. To help fix this, I did some research. Here’s what I found.
Orange tree leaves generally curl when the tree doesn’t get enough water. Simply, the leaves curl to conserve moisture. Other causes include extreme weather, pests, and diseases. To fix curled leaves, only water the orange tree when the top 2-4 inches of soil gets dry and check the leaves for any spots or pests.
So, while orange 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.
The most common cause of curling leaves on orange trees is under-watering. When under-watered, the orange tree’s leaves curl to conserve moisture and will eventually fall off. For best results, only water orange trees when the first 2-4 inches of soil gets dry and apply 2 inches of each compost and mulch.
Orange trees commonly use more water than other fruiting trees since they prefer to grow in warmer, tropical climates where there’s more evaporation and humidity. While there’s typically sufficient rainfall in tropical climates, a dry spell could cause the tree’s leaves to curl.
Many times, it’s difficult to tell if you’re over or under-watering your orange tree, but there’s a good trick to find out.
Push a finger 2-4 inches into the soil under the drip line of your orange tree. If the soil is bone dry, your tree needs more water. If the soil is sopping wet 1+ 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.
So, before you water your orange tree, push a finger into the soil and check its moisture. By only watering when the soil is dry, you’re ensuring the orange tree gets the appropriate amount of water.
If you find that your orange tree’s soil is staying sopping wet 1 or more hours after watering it, you can amend the soil with sand and compost to improve drainage. Potted orange trees that are waterlogged can be repotted with fresh soil as a last resort.
Once the soil is well-draining, apply 2 inches of each compost and mulch to the top of the soil, under the tree’s canopy.
Compost greatly improves the soil’s richness and therefore water retention. Every 1% increase in the soil’s richness can hold an additional 20,000 gallons of water per acre.
Mulch dramatically reduces evaporation from the soil and protects the soil (and beneficial soil life) from drying out with the sun and wind. This water retention goes a long way, especially in the hotter climates where orange trees like to grow. Some good mulches to use on orange trees are leaves, bark, straw, pine needles, and grass clippings.
When you apply compost and mulch, make sure to keep them at least 3 inches from the tree’s trunk to prevent mold and disease from spreading.
Orange tree leaves curl with extreme hot or cold weather or major swings in temperature of 30ºF or more. Typically, orange trees grow in temperatures between 35ºF-100ºF and can get stressed if their temperature falls outside of this range. To prevent leaf curl, keep your orange trees within 60ºF-80ºF if possible.
Hot weather can affect orange trees by drying out the leaves faster than the roots can send it moisture. When this happens, the leaves get scorched and curl to conserve moisture. If they get too hot for too long, the leaves will die and fall off the tree.
If your area gets too dry and hot for orange trees (commonly over 100ºF), there are some practices you can use to help cool them:
- Provide shade in the afternoon when the sun is at its hottest. You can shade the tree with an umbrella, shade sail, or other trees. Since we’re protecting the tree from the afternoon sun, shade from the west if possible.
- Apply 2 inches of compost and mulch on top of the soil to make sure it stays moist and doesn’t dry out in the sun and wind. Hot days with strong winds act like a blow dryer and can dry the soil (and tree) out in a matter of an hour.
- Plant in a north-facing direction if you get too much sun. If you can’t provide some shade for your orange tree, planting it facing north will minimize the sunlight it receives (just make sure it still has at least 4-6 hours to properly grow and fruit).
Cold weather is less likely to cause leaf curl on orange trees, but it’s still possible. While orange trees are typically hardier than other citrus trees, freezing temperatures can stress the tree and cause curled leaves. This is especially true if temperatures fall below 20ºF.
To help your orange trees during frost, consider some of these cold-weather tips:
- Insulate orange trees in times of frost. Planted orange trees can be wrapped with cardboard or bedsheets, while potted orange trees can be brought inside or buried in the ground. If you bring it inside, avoid placing it near the central heat as it will dry the tree and its leaves out (this happened to my potted Meyer lemon tree).
- Plant in a south-facing direction to maximize the sunlight the tree receives.
- Plant along a southern-facing wall to reflect the sunlight and warmth onto the tree. The wall radiates heat even into the night.
Pests and Diseases
Even though it’s not as likely as other causes, pests and diseases can lead to leaf curl and drop on orange 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.
Let’s take a look at the most common pests and diseases that cause orange tree leaves to curl.
Aphids and Spider Mites
Aphids are small bugs that suck the sap from under the orange tree’s leaves. This loss of moisture causes the leaves to curl, yellow, and fall off. Aphids come in multiple colors and can appear as white, yellow, or black specs, usually underneath the leaves. They can be treated by using water, neem oil, or ladybugs.
While aphids are the most common pest to cause curled leaves, others such as spider mites and mealybugs can also cause it. To remove these pests, use an organic pesticide or treatment such as neem oil.
When my potted Kaffir lime tree had aphids, I found that a simple jet of water was enough to knock them off and kill them. When doing this, you want to make sure the pressure is enough to blast them off, but not enough to rip up the leaves. For example, I used a hose without a nozzle and fitted my thumb over the opening.
Other treatments include neem oil and ladybugs. Neem oil traps the bugs, making them immobile and killing them, while ladybugs are a natural predator to aphids.
I’ve heard great things about both solutions and you can typically find them at your local nursery.
Bacterial or fungal diseases sometimes cause orange tree leaves to curl, yellow, brown, and drop. You can typically spot signs of a disease if the leaves have spots or if the bark is cracking and oozing sap. To treat these diseases, prune the infected areas and use an organic fungicide.
While diseases can cause curled leaves on orange trees, it’s not nearly as likely as under-watering or hot weather. However, if you see spots on the leaves or cracked bark, it’s likely a bacterial or fungal infection.
To treat, prune the diseased areas and apply an organic fungicide as directed. The best time to apply fungicide is right before the tree blooms as the flowers serve as an entryway into the tree’s immune system.
If you do find that your orange tree is affected by a disease, and you’re looking for a good, organic fungicide to use, check out this homemade, non-toxic fungicide by Stefan Sobkowiak – The Permaculture Orchard.