If you notice your tomato plant leaves curling up, don’t panic but do take action. There are several factors that can cause this response in tomatoes and most of them are fairly easy to manage if you catch the issue early enough. In this article, I’ll discuss some of the most common reasons for tomato leaf curl and offer tips for fixing them.

Tomato leaves may curl temporarily as a result of exposure to very high or low temperatures, drought conditions, or high winds. In other instances, you may see tomato plant leaves curling up and staying that way. This is a sign that something more significant is going on. By sorting out all of the potential reasons for tomato plant leaves curling up, you can find the right fix as needed and put preventative measures in place to help keep your tomatoes healthy and productive.

Tomato leaf curling – what does it look like?

If your plants are suffering from leaf curl, their foliage looks droopy with individual leaves curling up or rolling in on themselves. Sometimes leaf curl is relegated only to new growth or young leaves or leaflets. At other times, the entire plant becomes involved.

Typically caused by physical stressors in the immediate environment—think root damage or overly severe pruning, for example—physiological leaf roll usually starts with older leaves. Eventually, leaf roll symptoms will advance to the rest of the plant and affected leaves can feel thick and somewhat leathery or rubbery to the touch.

Is tomato leaf curl a big problem?

Depending on its cause, tomato leaf curl can be pretty serious. If left unchecked, tomato plant leaves curling up can affect flowering and your overall crop yields. What’s more, sometimes your tomato plants may die back altogether. That’s why it’s important to periodically check on plant growth and be on the lookout for abnormalities.

Reasons for tomato plant leaves curling up

Most often, you’ll see tomato plant leaves curling up as a temporary response to natural environmental stress. If you’ve ever forgotten to water your tomatoes on an unexpectedly hot day, you’ve likely already seen the result—rolled-up leaves on thirsty, hot plants. That said, other environmental factors, such as herbicide drift, can cause leaf roll and long-term damage. So can plant viruses and insect pest infestations.

1. Tomato varieties with leaves that curl

It’s worth noting that indeterminate varieties are a little more prone to tomato plant leaves curling up than their determinate counterparts. What’s the difference? Indeterminate tomatoes flower and fruit all season—usually on long vines that require more careful pruning and watering.

Determinate types, on the other hand, set all of their fruit at once and that’s that. Their growth habit is often bushier and more compact, and there’s a shorter window of opportunity for things to go wrong. Furthermore, because many commercial tomato growers seem to prefer them, they’ve bred disease-resistance into many determinate varieties.

2. Environmental stressors

If you live in an agricultural area and you notice leaf curl on your plants, the use of herbicides such as 2,4-d, Aminopyralid, Clopyralid, or Dicamba may be to blame. Similarly, neighbors in search of perfect lawns may also cause harm with weed-killing sprays applied to their lawn. Depending on wind speed and direction, weed killers can drift and do serious damage to your tomato patch, since tomatoes are very sensitive to these chemicals. In fact, herbicide residue may even be present in hay or similar agricultural products which can, in turn, affect plants living nearby, especially if that hay is used as a mulch in the garden.

Although different chemicals damage plants in slightly different ways, exposure generally causes new plant growth to twist and curl. Plants may even become discolored. Unfortunately, even if your tomatoes do happen to recover from initial herbicide damage, their tissues and fruits may contain trace amounts of chemical toxins.

Without the added chemical insult, a stiff wind alone can be enough to cause tomato leaves to curl or roll. Usually this is a temporary response as the affected plant tries to conserve moisture. For extra windy spots though, consider erecting a windbreak.

3. Water issues causing tomato plant leaves to curl

Too little or too much water is one of the more benign reasons for tomato plant leaves curling up. Leaves typically curl inward and upward when plants haven’t gotten enough water. As for tomatoes that have gotten too much water, they may have saggy stems and leaves that curl downward. And, if the situation is really dire, your plants’ roots can even begin to rot.

4. Heat or cold stress

There’s a lot to be said for properly hardening off bedding plants before establishing them in the garden. That’s particularly true for nightshade vegetables like peppers, eggplant, and tomatoes. They’re all very sensitive to abrupt temperature changes. Leaf curl on these plants early in the season can be a reaction to unexpected cold snaps or stress from sudden jumps in temperature. In both cases, all of the leaves on affected plants will curl as a protective measure.

In a pinch, you can use shade cloth or floating row cover to mitigate the effects of heat or cold stress. If you live in a very hot climate, you may need to shade your tomatoes during extra hot weather and redouble your efforts to water consistently.

5. Pests that cause tomato leaves to curl

Most often attracted to tender, new plant growth, aphids, spider mites, and other tiny opportunists simultaneously damage tomato plants and introduce pathways for disease which can lead to leaf curling. One of the worst offenders is the broad mite which is even tinier than the tiniest spider mite. While they snack, broad mites also leave behind a chemical that deforms plant leaves. Some gardeners rely on miticides or insecticidal soap for their control.

The sweet potato whitefly is another bad actor that’s commonly associated with tomato leaf curl. These whiteflies are a vector for multiple viruses which can wreak havoc on your tomato plants. Again, you may be able to knock down their numbers with an insecticidal soap. Just keep in mind that these products do not discriminate and will affect beneficial insects, too.

6. Tomato pathogens that cause tomato plant leaves curling up

Leaf curling or rolling may also be a sign that your tomatoes are diseased. Some culprits are bacterial. Some are soil-borne fungal pathogens which cause wilting diseases. And some of the most serious pathogens are viral.

Among the most common viral diseases that cause tomato plant leaves to curl or roll are tobacco mosaic virus, tomato yellow leaf curl virus, and tomato mosaic virus. With these, in addition to leaf deformities, you may begin to see yellow-to-bronze-colored spots across plant leaves and badly stunted plants overall. If you have infected plants, you’ll need to remove and destroy them. (That means keeping them out of the compost pile!) You should also wash and sanitize any garden tools which may have come into contact with diseased plants or soil. (A 10 percent bleach solution works well for this.)

7. Nutritional issues that cause tomato leaves to curl up

You can inadvertently trigger tomato leaf curl yourself by applying a fertilizer that contains too much nitrogen or by applying it at an inopportune time during the growing season. While nitrogen helps promote leafy, green growth, it can cause issues when your tomato plants are ready to begin flowering and fruiting. To get that job done, they need more phosphorus, as well as potassium and assorted micronutrients. Tons of nitrogen at that time can gum up the works.

Tips for preventing tomato leaf curl

Here are several actions you can take to avoid tomato plant leaves curling up in your garden:

• Start strong—Try disease-resistant tomato varieties like Celebrity or Mountain Magic and start with healthy plants that have been properly hardened off.
• Add organic nutrients—Ideally, the soil in your tomato bed should be fertile and well-draining. If you’re not sure about your soil quality, spring for a soil test and amend with plenty of organic matter like manure, compost, or worm castings ahead of time.
• Promote healthy roots—Careful cultivation around plants will help to control weeds and allow surface moisture to more easily reach plant roots. For extra protection, mulch the area with straw or leaf litter.
• Patrol for pests—As your plants develop, routinely monitor them for signs of whiteflies and other problem insects. These not only damage plants but also open them up to harmful pathogens.
• Water wisely—Tomatoes need about one to two inches of water per week and consistent watering is key. You might want to use a soaker hose or drip irrigation system to deliver water straight to the root zone since this can help to prevent the spread of some plant pathogens.

All ironed out

Remember, if you see the start of tomato leaf curl, odds are good that you can still turn things around. To help prevent the problem, look for disease-resistant tomato varieties and especially the determinate tomato types since these aren’t as susceptible to leaf roll.

When it comes to tomato leaf curl or roll, pathogen-infected plants and plants hit with drifts of herbicides are your worst case scenarios. If you’re contending with disease or herbicide damage, removing and disposing of these affected plants is the safest course of action.

Among the more common reasons for tomato plant leaves curling up? Physical damage to plant roots, stress from drought and heat, or feeding by insect pests. But there are ways to salvage your plants if they’re growing under these circumstances. Thoughtful, consistent watering and mulching, protecting plants with shade cloth, and managing insect pests all can contribute to a smoother season.

Have you faced any of these issues? Let us know how you fixed them in the comments below.

For more on growing AMAZING tomatoes, check out these additional articles: 

• Tomato growing secrets from a pro
• To pinch or not to pinch—that is the question (and here’s the answer) 
• Starting tomato plants from seed 
• How far apart to plant tomatoes
• How to make tomato plants grow faster