Skip to main content

It can be disconcerting when the leaves on your tomato plants start to curl and look unhealthy. There can be many causes, but it means your tomato plant is being stressed in some way. You will have to figure out what is causing the problem before you can address whatever the issue is.

Tomatoes are easy to grow, but they are sensitive plants. Weather, chemicals, disease, and under-watering are likely causes when the leaves start to curl. If leaves curl and appear dull, the most likely cause is under-watering.

When leaves start to curl, you need to get started on investigating the problem. Since there are several potential causes, it may take some time to find the issue. It could even be a combination of causes.

The good news is, leaf curl will not kill your plants and will not greatly affect the crop the plant will produce.

Still, it looks unsightly, and most gardeners would rather the leaves on their tomato plants were not curling. 

With some good observation skills, and trying different things, you can get your plants back on the road to good health.

Tomato leaves curling

Tomato leaves curling

Too much or too little water, too warm or too cool, are sometimes the cause and easily remedied by trial and error.

 If only new growth is affected, the problem is likely to be environmental, and even that can get complicated. 

The simplest answer is the best answer at times, so check the level of watering first to see if that is the issue.

 If the environment is not the issue, there could be a virus causing stress on the plant, and that can be the hardest to detect.

Tomatoes are sensitive plants.

Tomatoes are sensitive plants. They grow well without a lot of maintenance, but they can be affected by stress and disease. Several things can cause stress on a tomato plant, and leaves curling up or down is normally the first sign of stress.

If the issue is mites or a virus of some kind, it can spread throughout your garden, so it is important to remove those plants. 

Viruses or mites affect greenhouse plants more often than outside plants, but they can affect them outdoors as well. 

See this complete guide for getting rid of mites in your garden.

Why are my tomato leaves curling?

Why are my tomato leaves curling?

At the most basic level, leaves curl on tomato plants when the plant is stressed. 

The level of watering, or the amount of wind, can stress your plants. There can be other causes as well, such as herbicides and diseases.

There are 5 main reasons the leaves may begin to curl: weather damage, herbicide drift, herbicide residue, broad mites, and tomato viruses. Some are easier to detect than others. There can be multiple issues leading to further complications in your plants.

If a field nearby is being sprayed, the herbicides can drift onto your plants and harm them. 

It does not take much wind to move herbicides that have been sprayed, especially from an airplane. 

There can also be residue from last year’s herbicides in the soil that were used where your plants grow this year.  

See our complete article on tomato cold tolerance.

What causes tomato leaves to curl?

What causes tomato leaves to curl?

Tomatoes are finicky and sensitive. 

Leaves curl when there is something causing stress to the plants.

 It may take some time, but the cause can usually be found through some trial and error, and observation. 

Basically, anything that interferes with the plant’s growth and health causes stress, and that can cause the leaves to curl.

Leaf curling indicates that the plant is stressed but it is not always fatal.

The environment, access to water, heat, wind, and viruses, are just some of the culprits that could be causing your tomato plant leaves to curl. Leaf curling indicates that the plant is stressed but it is not always fatal. A small change to their environment usually suffices.

The wind that is hot and dry can cause leaves to curl, and that is called a physiological type of stress. 

It is a defense mechanism where the plant rolls up its leaves to preserve water, or prevent more water loss. 

A hot dry wind can dry out your plants even if you are watering them adequately. 

Viruses or mites are the least likely culprits, so save them to last in your search. 

See if you should take yellow leaves off plants.

Leaves twisting and curling

Leaves twisting and curling

Tomato plant leaves that are curling are plants that are stressed by the environment, chemicals, or viruses. 

There can be a variety of causes for leaf curling, and it may be a combination of causes. 

If your leaves are also twisting, you may find the solution easier than you thought. 

Twisting is caused by excessive heat and dry weather in most cases.

Heat and low moisture cause leaves to curl and twist.

Heat and low moisture cause leaves to curl and twist, especially toward the bottom of the plant. This is sometimes called a physiological leaf roll. The plant is using self-defense, curling up its leaves to keep them from drying out. The twisting usually indicates low moisture.

Whether the leaves are twisting in addition to curling can be a matter of interpretation.  

Curling slightly is the first sign of stress that the plant is feeling.  

If the problem is heat and lack of moisture, the leaves will also twist. 

Also, if the curling is not addressed in a reasonable amount of time, the leaves will start to twist, and that is just a continuation of the curling.

See what to do with old tomato soil. 

Tomato plant leaves curling down

Tomato plant leaves curling down

There are a lot of reasons leaves may curl on a tomato plant, and that makes it harder to determine the cause.

When the leaves are curling it may not even be anything to be concerned about, as curling rarely affects the growth of the plant or the number of tomatoes that will be produced.

Leaves will curl when the plant is under stress. The direction that the leaf is curling can indicate what is stressing the plant. If the curling is downward, the plant is not getting enough water and is in danger of drying out. 

An upward curl just means the plant is too hot, and as soon as the temperature cools a bit, it will unwind its leaves. 

A downward curl is bad and needs to be fixed sooner rather than later. It means the plant is not getting enough water.  

How do you treat tomato leaf curl?

How do you treat tomato leaf curl?

Sometimes leaf curling is only on one part of the plant, and when that is removed, the plant returns to normal. 

It isn’t always that easy, however. Some plants are more likely to have curling tendencies, so select plants that are resistant. 

Finding what is wrong is the first step in helping the plant thrive.

Tomato leaf curl is common, but usually not fatal to plants. Make sure the watering is adequate. If only some of the leaves are curling, cut them off. If the problem turns out to be a virus or mites, you will have to remove the plant before the problem spreads. 

The good news is a little leaf curling is not that serious of an issue. 

If you check the watering level and the soil, that may be all you will need. 

When it is spreading fast you should be more concerned.

Greg Volente

Greg Volente holds a Naturalist Certificate from the Morton Arboretum, worked for The Nature Conservancy leading environmental education programs and doing natural areas restoration, and worked in the soil science research & testing lab at Michigan State University. Besides gardening, he's an avid wildflower enthusiast, and loves botanizing, hiking, and backpacking.