Curling leaves usually mean your tomato plant is either too dry, too hot, or dealing with a pest or disease
Tomato leaves curl for several reasons, and the cause matters because the fix is different each time. The most common culprits are underwatering, heat stress, spider mites, early blight, and herbicide drift. You can narrow down which one by looking at the pattern of the curl, whether the leaves feel dry or wet, and what else is happening on the plant.
The good news is that leaf curl rarely kills a tomato plant outright, but it does slow growth and reduce fruit production. Catching it early and fixing the cause stops the problem from spreading to new leaves.
Key Takeaways
- Underwatering causes leaves to curl upward and feel papery; the soil will be hard and dry when you dig down two inches.
- Heat stress and low humidity make leaves curl inward at the edges, especially on hot afternoons; this is often temporary and reverses at night.
- Spider mites cause fine webbing on leaf undersides and yellowing between veins; they thrive in hot, dry conditions and spread quickly.
- Early blight starts with brown spots and rings on lower leaves, then causes them to curl and drop; it spreads in wet conditions.
- Herbicide drift from nearby lawn treatments can cause severe leaf distortion; there is no fix except time, but the plant usually recovers.
Underwatering and soil that dries out too fast
When a tomato plant does not get enough water, the leaves curl upward and inward, and they feel thin and papery when you touch them. The curl starts at the leaf edges and moves toward the center. The whole plant may look droopy even if you watered it yesterday, because the soil dried out faster than the roots could absorb water.
Check the soil by pushing your finger two inches down near the base of the plant. If it feels hard and dry, underwatering is the problem. Tomato plants need about one to two inches of water per week, depending on heat and soil type. Sandy soil dries faster than clay soil, so you may need to water more often if your garden has sandy soil.
Water deeply and slowly so the water soaks down to the roots instead of running off the surface. Water in the early morning so the soil has time to absorb moisture before the heat of the day. Mulch around the base of the plant with two to three inches of wood chips or straw to slow evaporation and keep the soil cooler.
Heat stress and low humidity
On very hot days—especially above 90°F—tomato leaves curl inward at the edges as the plant tries to reduce water loss through the leaf surface. This is called physiological leaf roll, and it is the plant protecting itself. The leaves may look almost normal again in the evening when the temperature drops, or they may stay curled if the heat was extreme.
Heat stress is not a disease, so you cannot spray it away. The plant will survive, but it may drop flowers and produce fewer tomatoes while the stress lasts. Shade cloth that blocks 20 to 30 percent of direct sun can help during heat waves. Water more frequently during hot spells—sometimes every day—because the soil dries much faster. Mulch also helps by keeping the soil temperature lower.
Low humidity makes heat stress worse. If your area is very dry, misting the leaves in the early morning can help temporarily, though it does not replace watering the soil. Focus on keeping the soil consistently moist rather than trying to change the air around the plant.
Spider mites and other common pests
Spider mites are tiny insects that suck juice from the undersides of leaves, causing them to curl, yellow, and eventually drop. You may see fine webbing on the leaf undersides, especially where the leaf meets the stem. The damage starts on the lower leaves and moves upward. Spider mites love hot, dry conditions, so they are most common in summer.
Look at the undersides of curled leaves with a magnifying glass or by holding a leaf up to the light. If you see tiny moving dots, you have spider mites. Spray the undersides of affected leaves with a strong stream of water from the hose to knock off the mites. Repeat every three days for two weeks. If the infestation is severe, neem oil or insecticidal soap can help, but follow the label directions and spray in the early morning or evening when bees are not active.
Keeping the soil consistently moist and the air around the plant humid also discourages spider mites. Remove heavily infested leaves to slow the spread.
Early blight and fungal diseases
Early blight is a fungal disease that starts on the lowest leaves as small brown spots with concentric rings—they look like a target. The leaves then curl, yellow, and drop. The disease spreads upward as the season goes on. Early blight thrives in wet conditions, especially when water splashes from the soil onto the leaves.
Remove all affected leaves as soon as you see them, cutting them off with clean scissors and throwing them in the trash (not the compost pile). Do not compost diseased leaves because the fungus can survive and spread next year. Water only at the soil level, never overhead, and water in the early morning so any splash dries quickly. Space plants far enough apart that air can move between them.
If early blight is severe, a fungicide containing copper or sulfur can slow it down, but it will not cure leaves that are already infected. Prune the lower 12 inches of leaves off the plant to remove the most infected area and improve air flow. The plant will keep growing new leaves at the top.
Herbicide drift from lawn treatments
If your tomato leaves are severely twisted, cupped, or distorted—especially if it happened suddenly after someone sprayed a lawn nearby—herbicide drift is likely the cause. Herbicides used on lawns to kill weeds can drift on the wind and land on vegetable gardens. The damage looks dramatic but is usually not permanent.
There is no way to reverse herbicide damage once it has happened. Remove the most severely damaged leaves to improve the plant's appearance, and let it grow new ones. Most tomato plants recover within a few weeks if the drift was light. If the damage is severe, the plant may take longer to bounce back or may not produce much fruit that season.
To prevent this, talk to neighbors before they spray, and cover your garden with a sheet if you know herbicide is being applied nearby. Plant a hedge or fence between your garden and treated lawns if drift is a recurring problem.
When to remove leaves and when to leave them alone
Remove leaves that are heavily damaged, diseased, or dead because they use energy the plant could put toward new growth and fruit. Cut them off with clean scissors or pruners, and do not leave stubs. Remove leaves that are touching the ground or splashing with soil water, because these are most likely to get early blight.
Do not remove leaves just because they are curled if the plant is otherwise healthy and growing. A few curled leaves from heat stress or mild underwatering will often uncurl once the problem is fixed. Removing too many leaves at once stresses the plant and can reduce fruit production.
If you are removing more than one-third of the plant's leaves at once, spread the removal over a few days so the plant is not shocked. Always leave enough leaves to shade the fruit, or the tomatoes may get sunscald—a white or yellow patch where the sun burned the skin.
Frequently Asked Questions
Can I use the same fix for all types of leaf curl?
No. Underwatering needs more water; heat stress needs shade and patience; spider mites need water spray or insecticidal soap; early blight needs leaf removal and better air flow; herbicide drift needs time. Watering more will not fix spider mites, and spraying fungicide will not fix underwatering. Look at the whole plant and the soil before you decide what to do.
Will curled leaves ever straighten out?
It depends on the cause. Leaves curled from heat stress or underwatering often uncurl once the problem is fixed. Leaves damaged by spider mites, disease, or herbicide will not straighten; you have to wait for new leaves to grow. New leaves are always better than trying to save old damaged ones.
Is leaf curl a sign the plant will die?
Almost never. Leaf curl slows growth and reduces fruit, but tomato plants are tough and recover from most causes of curling. Even plants with early blight or spider mites will survive and produce fruit if you catch the problem early and fix it.
Should I fertilize a plant with curled leaves?
Not until you fix the underlying problem. A plant that is underwatered or stressed by heat or pests cannot use fertilizer well, and adding more nutrients will not help. Water and fix the cause first, then fertilize once the plant is growing normally again.
Can I prevent leaf curl before it starts?
Yes. Water consistently and deeply, mulch to keep soil moist and cool, space plants for good air flow, water at soil level only, and remove lower leaves early in the season to prevent early blight. These steps prevent most leaf curl problems before they happen.