It’s not uncommon, but it is an early sign the tree is distressed.
Curling lemon tree leaves are triggered by environmental factors, maintenance errors, insect pests and diseases.
If hydration is adequate you may have an insect problem or nutrient deficiency.
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Take steps early to correct the problem before it impacts roots.
Once roots are affected, it’s more difficult to restore the tree to good health.
Lemons trees require a good amount of water and thrive better with deep watering once or twice a week.
Potted plants need to be watered more often.
If the trowel comes out clean and dry, water deeply.
Check for soil moisture in yourpotted lemon treewith your finger or a moisture meter.
Avoid using clay pots which leach moisture from soil.
Temperature Extremes
Lemon trees are hardy in USDA zones 8 through 11.
Other options include covering the tree with afrost blanketor tarp.
Remember to keep it from contacting the bark, which can lead to insect and disease problems.
Move potted plants out of direct sunlight and keep soil moist.
This problem is more endemic to trees grown outdoors; however,pruningis just as important for potted trees.
Nutrient Deficiencies
When leaves curl under the tree could lack sufficient nutrition.
Lemon trees need specific amounts of primary nutrients as well as micronutrients, especially calcium, iron and magnesium.
Apply a quality citrus fertilizer for trees grown in-ground in late winter, early summer, and early autumn.
Incorrect Watering
Leaf tips that curl under also indicate overwatering.Foliage turns yellowand drops.
In-ground trees need 1 to 2 inches of water twice weekly and more often during hot, dry weather.
Water thoroughly to soak soil to a depth of 2 to 3 feet.
Water potted plants every day or two to keep soil evenly moist.
This is especially important for trees moved outdoors during summer months.
Water less frequently during winter.
If ground is saturated, simply withhold water until excess drains.
Avoid planting trees in low spots or at the base of an incline where rainwater accumulates.
Don’t let your potted tree sit in standing water.
If the potting medium is extremely soggy, repot in fresh, dry material.
Allow the roots to dry out for several days before resuming a normal watering schedule.
The Asian Citrus psyllid leaves a white, waxy filament on distorted leaves.
Treat with a strong of water or apply a mild soap solution in cases of infestation.
Use similar treatment for psyllids or spray with insecticide.
Spider mites, mealybugs, and scaleare particular problems for potted plants grown indoors.
In addition to these pests, whiteflies and leafminers can damage leaves on your outdoor tree.
Treat both indoor and outdoor lemon treeswith neem oilor another horticultural oil.
Diseases
Lemon trees are vulnerable to several fungal and bacterial diseases that cause leaf curl.
Diagnosing Home Citrus Problems.
Arizona Cooperative Extension
Anthracnose.
University of California IPM
The Plant Doctor-Sooty Mold.
Mississippi State University Extension
Citrus Blast.
University of California Agriculture and Natural Resource
