Why are my tomato leaves curling?

Tomato leaves curl for several distinct reasons, some of which are harmless and some of which indicate serious problems. Physiological leaf roll is the most common cause: the lower and middle leaves roll upward along their midrib in response to heat, heavy fruit load, or aggressive pruning, and the plant otherwise looks healthy. This is normal and does not affect yield. Drought stress causes the leaves to roll or cup upward, particularly during the hottest part of the day, and the plant recovers once watered. Tomato Yellow Leaf Curl Virus (TYLCV) and other viral infections cause the leaves to curl upward and become pale yellow, stunted, and cupped, with no recovery after watering. Broad mites cause the newest growth to curl downward and become bronze or distorted. Herbicide drift from broadleaf herbicides like 2,4-D causes the petioles and stems to twist and the leaves to curl in unusual, asymmetric patterns. Overwatering causes downward curl and yellowing.

Is tomato leaf roll normal?

Yes, physiological leaf roll in tomatoes is entirely normal and very common. It typically affects the lower and middle leaves of the plant, which roll upward along their midrib so that the edges touch or overlap. The leaves remain firm and green, the plant continues to grow normally, and there is no effect on fruit production. Physiological leaf roll is most common on indeterminate tomato varieties, in hot weather, after heavy watering or irrigation, or after aggressive pruning or removing suckers that reduces the plant's leaf area relative to its root system. It requires no treatment. The key distinction from problematic curling: physiological leaf roll leaves are firm and green, the plant looks otherwise healthy, and the curling does not spread to new growth.

Why are my tomato leaves curling and turning yellow?

Tomato leaves that are curling and turning yellow at the same time most commonly indicate a viral infection, particularly Tomato Yellow Leaf Curl Virus (TYLCV). This virus causes the leaves to curl upward and inward, become pale yellow-green, feel leathery or stiff, and produce a cupped or bowl shape. The plant may also be stunted and fail to set fruit normally. TYLCV is spread by whiteflies and has no cure once the plant is infected; affected plants should be removed and disposed of to prevent spread. Yellowing curl combined with wilting and wet soil points to overwatering and root rot. Lower leaf yellowing and curl in otherwise-healthy plants can simply be older leaves naturally senescing.

Tomato Leaves Curling — Why It Happens and What to Do

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At a glance

Lower leaves rolling upward, plant otherwise healthy: Physiological leaf roll; normal, no action needed
Leaves cupping upward during heat, recovering in morning: Drought stress; water consistently and mulch
Leaves cupped and yellowing, new growth stunted: Viral infection (TYLCV); remove plant to prevent spread
Newest growth curling down and bronzing: Broad mites; treat with miticide or sulfur
Stems twisting and leaves curling asymmetrically: Herbicide drift; no cure, monitor and hope for recovery

Why tomato leaves curl

Tomato (Solanum lycopersicum) is one of the most popular garden plants in the world, and tomato leaf curl is one of the most common concerns among home gardeners. The important thing to know is that some leaf curling in tomatoes is entirely normal and requires no action, while other types of curling indicate serious problems that can destroy an entire crop. The key is to look at which leaves are affected, what direction they curl, what color they are, what the new growth looks like, and whether the plant has otherwise been under any stress. This guide walks through each cause so you can identify what is happening in your garden.

Cause 1: Physiological leaf roll (normal)

Signs: The lower and middle leaves are rolling upward along their midrib so the leaf edges curl toward each other or touch. The leaves are firm and green. The plant is growing normally and setting fruit. The curling is most pronounced in the afternoon and may relax slightly in the morning. No yellowing, no distortion of new growth, no insects visible.

Why it happens: Physiological leaf roll is a normal response in tomatoes, particularly in indeterminate varieties. It can be triggered by heat, high humidity, heavy fruit set, or pruning that alters the balance between root zone and leaf area. It is thought to be a self-protective mechanism that reduces water loss by reducing the exposed leaf surface area. It does not affect plant health, fruit quality, or yield.

What to do: Nothing. Physiological leaf roll does not require treatment. If the plant is in very hot, dry conditions and the curling is severe, consistent watering and a layer of mulch around the base to keep roots cool and moist will reduce the stress that triggers it. Do not apply fertilizer or pesticides in response to physiological leaf roll.

Cause 2: Drought stress

Signs: The leaves are cupping upward or rolling inward during the hottest part of the day, then relaxing partially in the morning before the day heats up. The soil is dry or inconsistently watered. The plant may wilt visibly in the afternoon. The leaves are still green and the new growth looks normal.

Why it happens: Tomatoes have high water demands, particularly when setting fruit and growing rapidly in summer heat. When soil moisture is inadequate, the leaves cup and roll to reduce water loss through the leaf surface. Unlike physiological leaf roll, drought-related curling is tied directly to soil moisture and worsens as the day progresses. Inconsistent watering, particularly wet-dry cycles, also stresses the plant and contributes to blossom end rot.

Fix: Water deeply and consistently. Tomatoes in the ground typically need 1 to 2 inches of water per week during fruit set, more in hot climates. Container tomatoes may need daily watering in summer. Apply a 2 to 3 inch layer of mulch around the base of the plant to conserve soil moisture and keep roots cool. Drip irrigation or soaker hoses deliver water directly to the root zone more efficiently than overhead watering.

Cause 3: Viral infection (Tomato Yellow Leaf Curl Virus and others)

Signs: The leaves are curling upward and inward and turning pale yellow-green, particularly on new growth. The leaves feel stiff or leathery and have a cupped or bowl shape. The plant may be stunted and producing fewer flowers than expected. Whiteflies may be visible on the underside of leaves. The curling does not improve after watering.

Why it happens: Tomato Yellow Leaf Curl Virus (TYLCV) is one of the most damaging tomato diseases globally and is spread by the silverleaf whitefly (Bemisia tabaci). Once a plant is infected, the virus systemically disrupts normal cell growth, causing the characteristic upward curl, yellowing, and stunting. There is no chemical treatment for viral infections in plants. Other viruses including Cucumber Mosaic Virus (CMV) can produce similar but often more mottled, mosaic-patterned symptoms.

What to do: Remove and dispose of infected plants in the trash, not the compost. Control whitefly populations on remaining plants with yellow sticky traps and insecticidal soap to reduce the spread vector. Plant TYLCV-resistant tomato varieties in subsequent seasons. Inspect transplants carefully before planting, as nursery stock can introduce the virus.

Cause 4: Broad mite infestation

Signs: The newest growth (growing tip, youngest leaves) is curling downward and may appear bronze, russeted, or distorted. The distortion is concentrated on emerging leaves rather than established ones. Broad mites themselves are microscopic and not visible to the naked eye, but the damage pattern is distinctive: new growth that looks twisted, curled down, and bronzed is the primary sign.

Why it happens: Broad mites (Polyphagotarsonemus latus) are extremely small arachnids that feed on growing tips, injecting toxic saliva that distorts developing cells. Unlike spider mites, which produce stippling on established leaves, broad mites concentrate damage on the newest tissue. The resulting bronzed, curled-down growing tip is often mistaken for herbicide damage, nutrient deficiency, or viral infection.

Fix: Treat with sulfur-based sprays or spinosad, applying to the growing tips where mites are active. Broad mites are resistant to many common miticides, so check the label for specific activity against broad mites before purchasing. Remove and discard heavily infested growing tips. Broad mites spread plant to plant on insects, tools, and clothing, so avoid working with affected plants and then moving to healthy ones without washing hands and tools.

Cause 5: Herbicide drift

Signs: The petioles (leaf stems) are twisting or curling, and the leaves are distorting asymmetrically rather than rolling uniformly. The stems may be thickening, bending, or producing abnormal growth. Multiple plants in a row or downwind direction are affected simultaneously. The damage appeared suddenly, possibly after a neighbor or nearby property applied a lawn herbicide.

Why it happens: Broadleaf herbicides including 2,4-D, dicamba, and clopyralid mimic plant hormones and cause uncontrolled growth when absorbed by non-target plants. Tomatoes are among the most sensitive plants to herbicide drift. Even very small amounts drifting from a neighbor's lawn treatment or from contaminated compost (clopyralid can persist in grass-based compost) can produce dramatic curling, twisting, and distortion in tomatoes. The damage pattern is unique: petiole twisting and leaf distortion rather than uniform upward or inward curl.

What to do: There is no chemical antidote. If the exposure was light, the new growth emerging after the drift event may be normal, and the plant may partially recover and produce fruit. If the exposure was heavy, the plant may not recover. Water the soil thoroughly to dilute any herbicide that may have settled in the root zone. If the source is contaminated compost, remove and replace the soil. Document the damage in case a neighbor's product is responsible.

Tomato Leaves Curling