Curling tomato leaves usually means the plant is stressed by heat, water problems, or pests—and the cause changes what you do next
Tomato leaf curl happens when the edges of the leaves roll inward or the whole leaf twists, and it is almost always a sign that something in the plant's environment or health has shifted. The three most common causes are heat stress (especially when temperatures spike above 85°F and the soil dries out), watering problems (either too much water sitting around the roots or inconsistent watering that swings between wet and dry), and pest damage (spider mites or whiteflies feeding on the undersides of leaves). Less often, it is a viral infection or a nutrient deficiency. The good news is that leaf curl is usually reversible if you catch it early and fix the underlying problem.
Key Takeaways
- Heat stress combined with dry soil causes the most common type of tomato leaf curl, and it usually improves within a few days once you water deeply and provide afternoon shade.
- Overwatering or poor drainage can cause leaves to curl upward, and the soil should feel moist but not soggy—if water pools on top, your drainage needs work.
- Spider mites and whiteflies leave tiny yellow spots on leaves before the curl appears, and you can spot them by looking at the undersides of affected leaves with a magnifying glass.
- Curled leaves on the lower part of the plant only may signal a nutrient deficiency, usually nitrogen or magnesium, which you can address with a balanced fertilizer or Epsom salt spray.
- If the curl spreads rapidly and the plant yellows or wilts despite proper watering, a viral infection may be present, and the plant should be removed to prevent spread to other tomatoes.
Heat stress and dry soil: the most common cause
When daytime temperatures climb above 85°F and the soil around your tomato plant dries out, the plant curls its leaves as a survival reflex—it is trying to reduce the surface area that loses water to the air. You will notice the leaf edges rolling inward or the whole leaf becoming slightly cupped. The plant is not dying; it is protecting itself. The leaves may look papery or feel crispy to the touch.
The fix is to water deeply at the soil level early in the morning, before the heat of the day. Water until the soil is moist 6 to 8 inches down—not just the top inch. If temperatures are forecast to stay above 90°F for several days, add afternoon shade by placing a shade cloth (30 to 50 percent density) on the south and west sides of the plant, or position a tomato cage with an old sheet draped over it. Remove the shade once the heat breaks. Within two to three days of consistent watering and cooler conditions, the leaves should begin to uncurl.
Overwatering and poor drainage: when the soil stays too wet
If your soil is constantly wet or water pools on the surface after you water, the roots cannot breathe and begin to rot. Tomato roots need oxygen, and soggy soil suffocates them. When root damage starts, the plant cannot move water and nutrients upward properly, and the leaves curl upward (rather than inward) and may turn yellow or feel soft and mushy.
Check the soil by pushing your finger 2 inches down. If it feels soggy, stop watering and let it dry out for several days. If water pools on top when you water, your soil drainage is poor—either the soil is mostly clay or the planting area is in a low spot where water collects. For clay soil, mix in 2 to 3 inches of compost or peat moss before planting next season. For a low spot, consider moving the plant to higher ground or building a raised bed. In the meantime, water only when the top inch of soil feels dry to the touch, and always water at the soil level, never on the leaves.
Spider mites and whiteflies: pest damage that causes curling
Spider mites are tiny arachnids (not insects) that live on the undersides of leaves and suck out the plant's fluids. Whiteflies are small white insects that do the same thing. Both leave tiny yellow or pale spots on the leaf surface first, and as the damage spreads, the leaf curls and may turn brown. If you look at the underside of a curled leaf with a magnifying glass, you may see fine webbing (spider mites) or a cluster of tiny white insects (whiteflies).
To confirm the pest, hold a white piece of paper under a leaf and tap the leaf gently—if tiny insects fall onto the paper and move around, you have whiteflies. For spider mites, look for fine webbing between the leaf and stem. Once you confirm the pest, spray the undersides of all affected leaves with a strong stream of water from the hose to knock off as many mites or insects as possible. Repeat every two to three days for two weeks. If the infestation is heavy, use neem oil or insecticidal soap according to the label directions, always spraying in the early morning or late evening when beneficial insects are less active. The curled leaves will not uncurl, but new growth should be normal once the pest population drops.
Nutrient deficiency: when curling starts on lower leaves
If only the lower, older leaves are curling and turning yellow while new growth at the top looks normal, the plant may be short on nitrogen or magnesium. Nitrogen deficiency shows as yellowing that starts at the leaf edges and moves inward, often with some curling. Magnesium deficiency causes yellowing between the leaf veins while the veins stay green, and the leaves may curl slightly.
For nitrogen deficiency, explore a balanced fertilizer (such as 10-10-10) according to the package directions, or side-dress the plant with compost. For magnesium deficiency, dissolve 1 tablespoon of Epsom salt in 1 gallon of water and spray the leaves in the early morning or late evening, or pour the mixture around the base of the plant. Repeat the Epsom salt spray every two weeks. The curled leaves will not recover, but new leaves should grow in normally within a week or two.
Viral infections: when curling spreads quickly and the plant declines
Tomato viruses such as tomato mosaic virus or tomato spotted wilt virus cause leaves to curl, mottle (develop patches of different colors), and become distorted. The curling spreads rapidly across the plant, and the plant may yellow, wilt, or stop growing even when watered properly. Viral infections are spread by insects (especially aphids and thrips) or by touching a diseased plant and then touching a healthy one.
There is no cure for a viral infection. If you suspect a virus, remove the entire plant and throw it in the trash (not the compost pile, where the virus could survive). Wash your hands and any tools you used with soap and water before touching other plants. To prevent viruses next season, control aphids and thrips with regular spraying, remove weeds (which can harbor viruses), and avoid handling plants when they are wet, since the virus spreads more easily on wet leaves.
When to call for help or remove the plant
Most leaf curl improves within a few days once you address the cause—heat stress, watering, or pests. If the curl spreads despite your efforts, the plant yellows or wilts even after watering, or you see signs of a viral infection (rapid spread, mottling, severe distortion), it is time to remove the plant. A declining tomato plant will not recover and will only spread disease or pests to nearby plants.
If you are unsure whether the problem is heat stress, a pest, or something else, take a photo of the curled leaf (including the underside) and bring it to your local cooperative extension office. They can identify the cause and recommend the best treatment for your specific situation. Most extension offices offer this service free of charge.
Frequently Asked Questions
Can curled leaves uncurl once they are damaged?
No. Once a leaf has curled and hardened, it will not flatten back out. However, the plant will produce new leaves, and those should grow normally once you fix the underlying problem. Remove severely damaged leaves if they are blocking air flow or look unsightly.
Is it safe to eat tomatoes from a plant with curled leaves?
Yes, if the curl is from heat stress, watering problems, or nutrient deficiency. If the curl is from a viral infection, do not eat the fruit—remove and discard the entire plant. If the curl is from spider mites or whiteflies, the fruit is safe to eat, but wash it thoroughly before eating.
Should I prune off all the curled leaves?
No. Leaves are the plant's food factory, and removing too many will slow growth and reduce fruit production. Remove only leaves that are severely damaged, blocking air flow, or touching the ground. Leave healthy-looking leaves even if they are slightly curled.
How often should I water tomatoes to prevent leaf curl?
Water deeply when the top inch of soil feels dry to the touch—usually once or twice a week depending on heat and rainfall. In very hot weather, this may be daily. The goal is to keep the soil consistently moist but not soggy. Mulch around the base with 2 to 3 inches of straw or wood chips to help the soil hold moisture evenly.
Can I use the same soil next year if my plant had a virus?
It is safer not to. Some tomato viruses can survive in soil for months. If you want to reuse the soil, replace the top 6 inches with fresh compost, or use the old soil for non-tomato plants. For peace of mind, use fresh soil for tomatoes the next season.