Tomato leaves curl because of heat stress, inconsistent watering, disease, or pests — and the fix depends on which one is happening

Curled tomato leaves usually mean one of four things: your plant is too hot or thirsty, it has a fungal or viral disease, spider mites are feeding on it, or it was exposed to herbicide drift. The curl itself is the plant's attempt to reduce water loss or a physical response to damage. You can stop it by identifying which cause is at work, then adjusting watering, temperature, air flow, or pest control. Most causes are reversible if you catch them early.

Key Takeaways

  • Heat stress and underwatering cause upward leaf curl as the plant tries to conserve moisture; water deeply at the soil line in early morning and provide afternoon shade in extreme heat.
  • Fungal diseases like early blight and septoria leaf spot cause downward curl and brown spots; remove affected leaves and improve air circulation between plants.
  • Spider mites cause fine webbing and stippled, curled leaves; spray the undersides of leaves with water or insecticidal soap every three days.
  • Herbicide drift from nearby lawn treatments causes twisted, cupped leaves that do not improve; move the plant if possible and wait for new growth.
  • Viral diseases like tomato mosaic virus cause mottled, curled leaves and have no cure; remove the plant to prevent spread to others.

Heat Stress and Underwatering Cause Upward Leaf Curl

When tomato leaves curl upward at the edges and the plant looks wilted even after watering, heat stress is usually the cause. Temperatures above 85°F slow the plant's ability to move water from the roots to the leaves fast enough, so the leaves curl inward to reduce the surface area losing water to the air. This is a survival reflex, not permanent damage — the leaves will uncurl once the plant cools down or gets more water.

Check the soil before you water: stick your finger two inches into the soil near the base of the plant. If it feels dry, water deeply at the soil line until water drains from the bottom of the pot or runs into the soil around the base. Water in early morning so the plant has moisture available before the heat of the day. In containers, tomatoes need water every one to two days in hot weather; in the ground, they need about one inch per week, but more during heat waves.

If temperatures are consistently above 85°F, provide afternoon shade with a cloth shade cloth (30 to 50 percent shade) or by planting taller crops nearby. Mulch around the base with two to three inches of straw or wood chips to keep the soil cooler and reduce water loss. Do not prune leaves to expose the fruit to more sun — the leaves protect the fruit from sunscald.

Fungal Leaf Diseases Cause Downward Curl and Brown Spots

Early blight and septoria leaf spot are the two most common fungal diseases on tomatoes. Early blight starts with brown spots ringed in concentric circles on the lowest leaves, then spreads upward. Septoria leaf spot shows small circular spots with dark borders and gray centers. Both cause leaves to curl downward, yellow, and eventually drop. These diseases thrive in warm, humid conditions and spread through water splash from rain or overhead watering.

Remove affected leaves as soon as you see spots — cut them off with clean scissors and throw them in the trash, not the compost. Do not compost diseased leaves because the fungus survives in plant material. Water only at the soil line, never on the leaves, and water in early morning so any splash dries quickly. Space plants at least two feet apart so air can flow between them; prune lower branches to improve air circulation near the base.

If the disease is spreading despite these steps, spray the plant with a fungicide labeled for tomatoes. Sulfur dust or copper fungicide work on early blight and septoria leaf spot; follow the label for timing and how often to spray. Most fungicides work best as prevention, so start spraying before you see disease if you live in a humid area or had these diseases last year.

Spider Mites Cause Fine Webbing and Stippled Leaves

Spider mites are tiny arachnids that feed on the underside of leaves, sucking out plant cells. Infested leaves develop a pale, speckled or stippled appearance, then curl and turn brown. You may see fine webbing on the undersides of leaves or between stems. Spider mites thrive in hot, dry conditions and reproduce quickly — a population can explode in two to three weeks.

Check for mites by holding a white paper under a leaf and tapping the leaf sharply; if mites are present, you will see tiny moving specks fall onto the paper. Spray the undersides of affected leaves with a strong stream of water from the hose to knock off mites and their webbing. Repeat every three days for two weeks. If the infestation is heavy, spray with insecticidal soap or neem oil, coating the undersides of leaves thoroughly. Reapply every three to seven days as directed on the label.

Prevent spider mites by keeping the plant well-watered — mites prefer dry conditions — and by misting the leaves with water in the early morning. Avoid over-fertilizing with nitrogen, which produces soft new growth that mites prefer.

Herbicide Drift Causes Twisted, Cupped Leaves

If your tomato leaves are twisted, cupped, or distorted in shape, and the damage appeared after someone sprayed a lawn or garden nearby, herbicide drift is likely the cause. Herbicides like 2,4-D (a common weed killer in lawn treatments) are volatile and can drift on the wind for hundreds of feet. The damage is not reversible on affected leaves, but the plant will produce new, normal growth if the exposure was a one-time event.

Move the plant away from the source of drift if possible. Do not spray anything else on the plant while it is stressed. Water it regularly and let it recover; new leaves should emerge normal within one to two weeks. If the plant was severely damaged or if drift exposure happens repeatedly, the plant may not recover enough to produce fruit.

Viral Diseases Cause Mottled, Curled Leaves and Have No Cure

Tomato mosaic virus and tomato spotted wilt virus cause leaves to curl, mottle (show a patchwork of light and dark green), and become distorted. Infected plants often produce few or misshapen fruit. Viruses are spread by insects (especially aphids and thrips) or by handling plants — you can spread it by touching an infected plant and then touching a healthy one.

There is no cure for viral diseases. Remove the infected plant entirely and throw it in the trash to prevent the virus from spreading to other tomatoes or peppers in your garden. Wash your hands and disinfect any tools you used on the plant by wiping them with a cloth soaked in a 10 percent bleach solution (one part bleach to nine parts water).

Prevent viral diseases by controlling aphids and thrips with insecticidal soap or neem oil, and by avoiding handling plants when they are wet (which spreads the virus more easily). Plant resistant varieties if viruses were a problem in your garden last year — look for varieties marked with a V or VF on the label, which indicates resistance to verticillium and fusarium wilts.

When to Remove a Plant and When to Keep Treating It

Remove the plant if it has a viral disease, or if it is so severely damaged by heat, pests, or disease that it has lost most of its leaves and is not producing fruit. A plant with a few curled leaves from heat stress or early blight can recover and still give you a harvest if you address the cause.

Keep treating if you see improvement within one to two weeks — new leaves emerging normal, spots stopping their spread, or the plant standing upright again after watering. If the problem is getting worse despite your efforts, or if the plant is not producing any fruit by mid-summer, it is usually better to remove it and plant something else in that spot.

Frequently Asked Questions

Can I eat tomatoes from a plant with curled leaves?

Yes, if the curling is from heat stress or underwatering. Fruit from plants with fungal diseases or spider mites is safe to eat — wash it well before eating. Do not eat fruit from a plant with a viral disease, because the virus can survive in the fruit and spread if you handle other plants afterward.

Will curled leaves uncurl on their own?

Leaves that curled from heat stress or underwatering will uncurl within a few hours to a day once the plant cools down or gets water. Leaves damaged by disease, pests, or herbicides will not uncurl — they will eventually yellow and drop. New leaves will grow in normal if you fix the underlying problem.

Is it safe to use fungicide on tomatoes I plan to eat?

Yes, if you follow the label directions. Most fungicides labeled for tomatoes are safe for edible crops when used as directed. Wash the fruit before eating. Sulfur and copper are organic options if you prefer them.

How do I know if my tomato plant has spider mites or a disease?

Spider mites leave fine webbing and affect the undersides of leaves first; you can see the tiny mites with a magnifying glass. Fungal diseases show spots or rings on the leaf surface and do not have webbing. Viral diseases cause mottling (a patchwork pattern) rather than spots. Check the undersides of leaves with a white paper underneath to confirm mites.

Can I prevent leaf curl by changing how I plant tomatoes?

Yes. Space plants two feet apart for air flow, water at the soil line only, mulch to keep soil cool and moist, and choose disease-resistant varieties marked with V or VF. In very hot climates, plant tomatoes where they get afternoon shade. These steps prevent most causes of leaf curl.