Troubleshoot the system before you change the inputs.
Symptoms
- Leaf edges roll upward and inward, mostly on the lower leaves, while the leaf otherwise looks normal.
- New leaves at the top are twisted, narrow or strap-shaped and stay small.
- Leaves are small, crumpled and yellowing at the margins on a stunted plant.
- Leaves curl and the undersides turn bronze, or tips are sticky with insects on them.
Possible causes
- Physiological leaf roll from swings between dry and wet soil, heat, or excess nitrogen.
- Herbicide injury, usually from drift or treated material reaching the plant.
- Aphids or broad mites feeding on the growing tip.
- Tomato yellow leaf curl virus, spread by whiteflies and infected transplants.
Quick fixes
- Check the pot with a finger or by weight and water on a steady schedule rather than letting it dry out and then soaking it.
- Shade the plant from the hottest afternoon sun when temperatures go above 95 °F, the threshold the PNW plant disease handbook gives.
- Look at the growing tip and the underside of new leaves with a hand lens before treating anything.
- Isolate or remove plants with stunting and crumpled yellow leaves, and check for whiteflies.
Tomato leaf curl: how the causes differ
| Cause | Which leaves | What the leaf looks like | Other clue |
|---|---|---|---|
| Water swings, heat | Lower leaves first | Edges roll up and in, rest of leaf looks normal | Dry spells followed by heavy watering, hot spell |
| Excess nitrogen | Rolled leaves, often many | Thick, dark green | Lush growth after heavy feeding |
| Herbicide | Youngest, top growth | Twisted, strappy, small | Neighbours' plants or treated material nearby |
| Aphids or broad mites | New growth at the tip | Distorted; mites bronze the underside | Insects, honeydew, or bronzing with green veins |
| Yellow leaf curl virus | Whole young plant | Small, curled up, crumpled, yellow margins | Stunting, flower drop, whiteflies |
Most curling tomato leaves are physiological leaf roll: the edges of lower leaves roll up and in after dry-wet swings or a hot spell, and the plant keeps cropping. If instead the new growth at the top is twisted and strap-like, or the whole plant is stunted with crumpled yellow leaves, you are looking at herbicide, pests or virus. The pattern tells you which, so start with where on the plant the curl sits.
Curl is only one symptom. If your plant is also yellowing or drooping, tomato leaves turning yellow and tomato plant wilting cover those. For peppers, see pepper leaves curling; for basil and other herbs, see herb leaves curling.
Lower leaves rolling up: the harmless one
The Pacific Northwest plant disease handbook describes physiological leafroll as a case where “the edges of many but not all leaves on affected plants roll upward and inward.” It calls the cause “a physiological response by tomato plants to fairly extreme changes in soil moisture levels,” with high nitrogen, phosphorus deficiency and heavy pruning during dry soil as other contributors. The handbook adds that high-yielding and indeterminate varieties seem more sensitive, and lists planting determinate varieties as a control. The same page states that it “does not affect fruit yield or quality.”
The Vegetable Crops Hotline adds the discriminators. Hot and dry conditions curl leaves, but “except for the margins of the leaves which are rolled up, the leaves generally appear normal,” and lower leaves are often affected first. Excess nitrogen also curls leaves, and the rolled leaves are often thicker and dark green.
In a pot, soil moisture swings are easy to cause: a small container dries out fast in July, then gets a deep soak. The fix is steadier watering, not more water. The Pacific Northwest plant disease handbook recommends a well-timed irrigation schedule that prevents overly dry and overly wet soil, balanced fertilizer, avoiding excessive pruning of indeterminate types, and protecting plants from temperatures above 95 °F. For the shading and watering side of a hot spell, see protecting container plants in a heatwave.
Whether rolled leaves flatten again depends on the stress. The Pacific Northwest plant disease handbook says the rolling “can be transient or may persist throughout the rest of the growing season,” and the Vegetable Crops Hotline says lower leaves “may recover if environmental stresses are reduced.” Judge new growth only for herbicide and pest curl, which does not reverse.
Twisted, strappy new growth: herbicide
University of Maryland Extension says tomatoes are “very sensitive to 2,4-D,” and that injured “leaves become twisted, curled, and strappy and stay small in size,” with injury seen on the youngest leaves. The Vegetable Crops Hotline makes the same point: severely deformed or twisted curl suggests herbicide, and the symptom is more pronounced at the top of the plant where new growth appears.
That is the opposite of leaf roll, which is a curled margin on an otherwise normal leaf and shows mostly on the old leaves. Maryland notes that herbicides can drift many feet from where they are applied. On a balcony or rooftop, think about lawn treatments nearby, sprayed railings or weeds, and any treated material you added to the pots. Rule out insects, disease and nutrient problems first, as Maryland advises.
The bad news is that “plants rarely outgrow the injury caused by this growth regulator.” Maryland’s advice is to remove the plants and replant if you can. If the whole plant is badly twisted, that is the realistic option.
Pests that distort the growing tip
Two common pests distort new growth on tomatoes. Both need a close look. UC IPM also lists thrips for distorted, curled shoot tips, identified by dark specks of excrement; see thrips on indoor herbs for how to confirm them.
Aphids. UC IPM notes that some aphid species inject a toxin that makes leaves curl, and the curl stays after the aphids are gone. Look for clusters on tips and undersides, plus sticky honeydew. The isolate-and-rinse routine in aphids on indoor herbs works the same way on a tomato you can reach.
Broad mites. University of Maryland Extension describes the females as “oval, 0.2 mm long and are yellow or green,” so you will not see them with the naked eye. They feed near the growing point on the underside of leaves, twisting and distorting the young leaves, and “more serious infestations cause leaf bronzing leaving the main veins green against the brown leaf tissue.” Lower leaves often stay unaffected. Maryland reports them as a problem in tomato high tunnels, and also warns their damage “can look similar to the damage caused by viruses, herbicides or nutrient deficiencies,” so confirm with a lens before treating. Before spraying anything on a plant you will eat, read the label: see choosing a pest treatment for edible plants.
Small, crumpled, yellow, stunted: virus
UC IPM describes tomato yellow leaf curl virus: “leaves of infected plants are small and curl upward; and show strong crumpling and interveinal and marginal yellowing.” Infected plants are often stunted and bushy, and flowers commonly fall off before developing. UC IPM says the virus is spread short distances primarily by Bemisia whiteflies, and over long distances “primarily through the movement of infected plants, especially tomato transplants.” That makes a bought seedling worth inspecting for whiteflies before it joins your other plants.
If you see this pattern, look for whiteflies on the undersides (see whiteflies on balcony vegetables). UC IPM’s management list for growers starts with TYLCV-resistant varieties and virus- and whitefly-free transplants, and recommends removing diseased plants when infection is low. Treat that as a reason to buy resistant varieties next season rather than as a cure.
UC IPM also describes beet curly top virus, spread only by the beet leafhopper: plants turn yellow to bronze with purple-tinged leaves, stop growing and become stiff. UC IPM’s control advice for it is aimed at commercial fields.
Quick decision order
- Are the lower leaves rolled at the edges, otherwise normal? Even out watering and shade from heat.
- Is new growth at the top twisted and narrow? Think herbicide.
- Is the tip sticky, or are undersides bronzed? Use a hand lens for aphids and mites.
- Is the plant stunted with small, crumpled, yellow leaves? Check for whiteflies and suspect virus.
Sources
- PNW Plant Disease Management Handbook: Tomato physiological leafroll
- Vegetable Crops Hotline: Tomato leaf curling
- University of Maryland Extension: Herbicide damage on vegetables
- University of Maryland Extension: Broad mites on high tunnel tomatoes
- UC IPM: Tomato yellow leaf curl
- UC IPM: Curly top virus in tomato
- UC IPM Pest Notes: Aphids
Tomato leaf problems
Curl overlaps with yellowing, wilting and spotting, so use these pages to separate the signals.
Common questions
Is tomato leaf curl harmful to the plant?
Usually not. The Pacific Northwest plant disease handbook states that physiological leafroll does not affect fruit yield or quality. Herbicide injury, mites and viruses are the exceptions: University of Maryland Extension says tomatoes rarely outgrow growth-regulator injury, and UC IPM lists stunting and flower drop for tomato yellow leaf curl virus.
Why are my tomato leaves curling upward?
Upward rolling along the edges, mostly on lower leaves, is the classic pattern for physiological leaf roll, tied to big swings in soil moisture, with heat and excess nitrogen as other triggers. Upward curl with crumpling and yellowing on a small, stunted plant is the pattern UC IPM gives for tomato yellow leaf curl virus.
Will my tomato leaves uncurl?
Often, if the cause was physiological: the Pacific Northwest plant disease handbook says leafroll can be transient, and the Vegetable Crops Hotline says lower leaves may recover once heat and water stress ease. Curl from herbicide or an aphid toxin does not reverse, so judge those causes by new growth: twisted, strap-shaped leaves keep coming if the cause was a growth-regulator herbicide.
Should I pull a tomato with curled leaves?
Not before you have checked the pattern. Physiological roll needs no removal. University of Maryland Extension advises removing and replanting after herbicide injury, and UC IPM advises virus-free, whitefly-free transplants and resistant varieties for tomato yellow leaf curl virus.
Related guides
Tomato leaves turning yellow in pots: read the pattern first
Which leaves yellow, and in what pattern, tells you whether a potted tomato is hungry, waterlogged, short of magnesium or diseased.
Tomato plant wilting even though you water it: heat, roots, or disease
Midday droop that clears by evening is usually heat. Wilt that stays after watering points to rotting roots or a vascular disease, and a cut stem tells you which.
Pepper leaves curling: mites, aphids, heat, or virus
Curling pepper leaves are harmless in a heat wave and a warning when they come with distorted new growth. Here is how to tell the two apart.