Why Are My Tomato Leaves Curling?

If you’re wondering; why are my tomato leaves curling? in this article, we are going to discuss everything you need to know about tomato leaf curling. This includes causes and possible remedies. By the end, you should have a greater understanding of why your tomato leaves are curling and how to treat tomato leaf curl.

While tomato is one of the easiest vegetables to grow in the garden, they are also a cause of much heartache and anxiety, especially for newbie gardeners. This is because, more often than not, several problems like diseases, pests, and deficiencies have to be dealt with in the course of growing them.

Leaf curl, also known as leaf roll, is one of the most common problems associated with tomatoes especially the non-heirloom tomato species. They can show up at any stage but fortunately, they don’t always spell gloom and doom.

Why Are My Tomato Leaves Curling?

You’d get this question fairly often from anxious gardeners just cutting their teeth in tomato farming. This is understandable because nobody wants to see those beauties getting all shrivelled and diseased.

The tomato curling leaves problem has several causative agents. This can sometimes make it hard to isolate the cause. Invariably,  it becomes harder to prevent it, because you just don’t know what might trigger it despite your best efforts.

Below are some of the factors responsible for tomato leaf curl in your tomato plants.

Environmental factors

Different stressors from the environment are known causes of leaf curl in tomato plants especially the seedlings. Below are some typical weather-linked tomato leaf curl causes:

Hot or dry weather  

Numerous gardeners sometimes notice that their tomato seedlings bought in the spring would thrive for a bit before developing leaf curl suddenly. This can happen when the weather becomes dry and too hot.

In cases like this, the leaf curl inwards, affecting the older leaves at the bottom of the stem before moving up the stem. Though the affected leaves would still retain that green color, they become leathery in appearance.

Cold and wet weather

Some tomato plants react to a dip in temperature accompanied by an increase in the amount of moisture in the air.

Here too, the leaves can curl upwards and take on that leathery appearance which is a defensive mechanism to repel the additional moisture. Staked and pruned tomato plants can be very susceptible to this problem.

Windy weather

Leaf curl in tomatoes caused by wind is mostly associated with indeterminate tomatoes species. It gets worse if the high winds combine with low humidity and dust.

The most susceptible leaves in the garden are those linked to plants that are improperly staked or supported. The plants react to the wind stress by curling the leaves while the plant itself can become twisted. It is not uncommon for the edges of the leaves to start dying before the curling and twisting of the leaves and plant respectively.

Remedy – High winds cause this condition because the wind is drying out the leaves at a faster rate than the plant is pulling up moisture from the soil. Protecting the tomato plants with a fence or protective shrubs should help resolve the problem.

For heat-related leaf curls, installing a simple shade to cover the plants when the sun is hottest should do the trick. But you must remember to remove the shade in the mornings and evenings. Your plants need that exposure to the sun to thrive.

Improper Gardening practices

Several gardening errors occur when carrying out routine tasks. These are stuff most gardeners take for granted, but unfortunately, as you’d read below, some of these errors lead to curling leaves in tomato plants.

Watering  

Over-watering is not good when it comes to gardening. If the soil is saturated with too much water (or if there is too much moisture around the root system or stagnant water on stems and leaves), air pockets are eliminated creating ideal conditions for root rot and infections.

Apart from causing the tomato leaves to curl, root rot also causes a change of color from green to a sickly brown and drooping of leaves.

Pruning

While diligent and regular pruning is beneficial to tomato plants, overdoing it, especially in young plants yet to become established, stresses the plant enough to develop the condition.

On the other hand, insufficient pruning produces too many leaves and foliage all competing with the tomato fruits for the plant’s resources. This stress is a reason enough for the leaves to curl.

Remedies – If you grow indeterminate tomatoes, a fine balance between over- and under-pruning can be achieved with a bit of pruning by cutting off the suckers between the lateral and main stems.

It is not advisable to prune determinate tomato plants.

Overall, pruning is vital in improving growth and air circulation. But the aim is always to target that sweet spot where you never prune more than is necessary. But always prune dead and diseased leaves to help keep the plants healthy.

For watering errors, you could adjust your schedule and perhaps use a moisture monitor to check how soggy the soil is. You could also use your fingers to check for soil sogginess. And most importantly, allow the soil to drain fully before watering again.

Sprayed herbicides

Tomatoes are very sensitive to chemicals like 2,4-Dichlorophenoxyacetate (Herbicide 2,4-D) found in herbicides. Sometimes, these chemicals are carried by the wind and deposited in tomato gardens.

Given enough time, tomatoes impacted by these chemicals would develop tomato curling leaves disease. The physical signs include malformed fruits that are unsafe for consumption, twisted plants, yellowing leaves, and leaves that curl downwards.

Remedy – Unfortunately, there is not a lot that can be done to reverse the damage. The best is to hope that the damage is too mild to affect new growth.

The good news is that this problem is not common. Unless your tomato patch is close to crops that would be sprayed, your tomatoes would never experience it.

READ: Can You Spray Weed Killer in A Vegetable Garden?

Contaminated compost

Gardens do exceptionally well with the addition of compost to the soil. Apart from ensuring optimal growing conditions for plants, compost also discourages weeds and can eliminate plant pathogens.

But if you buy your compost from sellers who collect their manure or hay from fields/farms sprayed with herbicides, you’d inadvertently introduce herbicide. to your garden. This can damage the leaves or even kill the plants.

Remedy – You simply have to get your compost from a trusted source all the time. Or you could verify the source of the hay or manure before buying.

Too much fertilizer

Tomato plants, including young seedlings, can experience leaf curl as well as spindly stems/limbs when too much fertilizer is applied.

A high concentration of nitrogen in the soil, apart from damaging the leaves, can also affect the roots.

Remedy – Problems related to fertilizer and excess soil nitrogen get resolved naturally over time. But you could prevent it from happening by applying the right amount of fertilizer and sticking to the instructions to avoid over-fertilizing the plants.

Insects

Two types of insects are implicated here. These are:

Aphids

There are over 400 species in this family of garden pests. If left to thrive, aphids would attack tomato plants leading to stunted growth, smaller fruits, and puckered, pale yellow leaves that curl backwards.

Broad mites

These insect pests attack a wide range of garden plants including tomatoes. They attack mostly young, tender leaves causing brown-coloured leaves and upward curling leaves.

Remedy – Look on the underside of the leaves. You’d find them there if they are the cause. Use insecticidal soaps to control them. But you have to uproot and destroy plants that are seriously damaged.

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Viral disease

Although hundred of viruses can lead to leaf curling, they are less common as causes of this condition in tomatoes.

Three are worth mentioning here:

Tomato mosaic & tobacco mosaic viruses

Their symptoms on tomato plants are similar. The plants can become stunted and with the leaves curling upwards.

Tomato yellow leaf curl virus (TYLCV)

Discovered in America in 2007 and transmitted by the sweet potato whiteflies, it is a more damaging viral disease capable of affecting large swathes or whole farms.

Stunted growth, limited fruit yields, yellow coloration along the veins of leaves, and upward curling leaves are the symptoms of this infection.

Remedy – The best remedy for tomato viral diseases, once identified, is to remove the plants and destroy them to prevent the infection from spreading to other plants.

Prevention involves cultivating hybrid tomato varieties, like Health Kick and Sophya, that are resistant to the virus.

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