Tomato plant pruning: Leaves curling up or turning yellow? How to fix ‘stressed’ plants

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Yellow, cupped, or curled-up leaves can all seem problematic while growing your own tomatoes, but it doesn’t always mean that your plant will fail. In fact, this easy-to-grow plant is hard to kill off, and can easily be fixed if you notice curling leaves or a yellow-hue taking over the foliage. These are the common causes of curling, yellow tomato leaves and exactly how to fix them.

What causes tomato leaves to curl?

According to the experts at, tomato plants are very sensitive, so it can often be a sign of stress when their leaves start to curl upwards at the edges.

While stress is not ideal for plants, it’s not fatal and usually won’t affect your yield long term, but what causes the plant to get “stressed” in the first place?

Excessive pruning

Not every gardener chooses to prune tomato plants, but if you do, it is important to avoid overdoing it.

Pruning your tomato plants more than necessary results in stress which causes the leaves to curl.

Constantly cutting back the plant also means it is more exposed to the sun, making it susceptible to heat damage as a result.

If you are in favour of tomato pruning, focus on pinching off the suckers between the main and lateral stems rather than cutting back the entire plant.

To help an over-pruned tomato plant recover, simply leave it be to allow the stress to resolve itself.


Heat can cause tomato leaves to curl up as a way of reducing the surface area exposed to the sun, which helps to minimise the amount of moisture lost through the foliage.

While watering may seem like the obvious fix to a plant that has had too much sun, it could actually do more harm than good.

According to Next Level Gardening, this is because leaf curl is generally not caused by a lack of water in the soil, but by the plant losing more water through the leaves than it can absorb from the roots.

Once a heatwave passes, the problem should fix itself so there is no need to water your tomatoes more excessively.

However, in prolonged periods of hot weather, it is best to use shade cloth to help keep the plant from dropping its flowers and stop the leaves from curling.

What causes tomato leaves to turn yellow?

In addition to leaf curling, discolouration can also occur when tomato plants are exposed to environmental stress, or infected with a disease.

Herbicide drift

Another cause of leaf curl is herbicide drift. This can cause discolouration, a drooping stem, and cupped leaves which curl inwards at the edges.

Herbicide drift happens when herbicide is sprayed close to, but not directly onto the tomato plant, and the residue drifts over onto the leaves.

Unfortunately, there is no way to recover leaves damaged in this way. New growth may grow unaffected if the exposure was mild, but the yield of the plant is likely to be impacted. If the problem is severe, the plant may not recover.

Luckily, this issue is not very common and is unlikely to affect your tomato crop severely unless it is consistently exposed to the herbicide.

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Watering incorrectly

Giving your plant too much, or not enough water can both cause tomato leaves to turn yellow.

If this is the most likely cause of your discoloured plant, it is best to soak the plant at short intervals rather than water it on a daily basis.

Gardening Know How said: “Soak tomato plants thoroughly once every five to seven days, depending on weather and soil type.

“Let the soil dry between watering and never allow the soil to remain soggy.”

Once the plant has recovered, establish a new watering schedule, making sure to water the plants carefully at the base only.

Yellow leaf curl virus

Yellow leaf curl virus affects tomato plants by causing the leaves to curl and turn pale green or yellow at the edges.

Rather than rolling completely inwards as in stress-related cases, the virus causes the leaves to fold upwards, creating a cup-like shape.

Yellow leaf virus is spread by whiteflies who will carry the disease to all of the tomatoes in your garden, and any other tomato-related plants.

There is no single remedy for this type of virus, so the only solution is to remove the infected plants in order to stop the spread of the disease.

Keeping your garden clean, using reflective mulch and row covers can help to deter whiteflies off your plants in the future.

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