Fresh tomatoes in your garden are an indispensable attribute of many households. What could be more exciting for a gardener than having delicious vegetables grown with his own hands? But things do not always go smoothly and with tomatoes sometimes difficulties arise.
Stress from unsuitable growing conditions, too little water, lack of nutrients, and Tomato yellow leaf curl virus are the main reasons for tomato leaves curling. To fix curled leaves, protect the tomato from the scorching sun and heat, also water it when the soil dries out to 1 inch. In addition, fertilize the plant at least twice a season and treat it for pests.
Improper growing conditions can cause tomato leaves curling
Tomato leaves curl because of temperature stress.
In most cases, worsening growing conditions will cause tomato leaves to curl.
First of all, this can happen in extreme heat. Tomatoes are heat-loving plants, but temperatures above 90°F (32°C) can cause stress and cause the leaves to curl up. This happens because the roots are unable to put enough water into the leaves even if the ground is moist. By curling (folding) the leaves, the tomato reduces the area of moisture evaporation, thereby avoiding the desiccation of the leaves.
The second case is when there is too much sun. The tomato prefers direct sun all day. But in midsummer, the sun is very intense, and if you live in the south, the plant can get stress or even sunburn. Very often heat and sun work together and can greatly affect the appearance of the tomato.
Usually, the curling of the leaves from the heat and sun is not fatal. Curled leaves probably won’t straighten out anymore, but the tomato will live and bear fruit.
In some percentage of cases, the sun and heat can still damage tomato leaves. If you want to help your tomato install a shade net over it. The netting should filter at least 50% of the sun’s rays. When the heat subsides, remove the screen immediately so the tomato gets enough light.
If the bright sun and heat last long, then shade the tomato only from the sun in the middle of the day. That is, the tomato should receive direct sunlight in the morning and evening. Because staying in full shade for a long time will also lead to negative effects.
Also, sometimes the curling of the leaves is due to cold weather or cold winds. Once the cold weather is gone, the plant will continue to grow normally. But if you want everything to be perfect, cover the tomato if the weather forecasters pass a cold snap. Or move it to a sheltered location if it’s growing in a container.
Watering issues
Tomato leaves curling because of underwatering.
Tomatoes need a lot of water for normal fruiting. But in a summer drought, there may not be enough water in the ground, causing the leaves to curl for the same purpose as in the previous case. Curled leaves evaporate less water in hot weather.
Tomatoes grown in pots are the most commonly affected by thirst. In the summertime, the soil in a pot that is placed in a sunny spot can dry out within a day. If you don’t water in the evening, the leaves can curl down the next day.
To solve the problem of lack of water, you need to constantly monitor the moisture of the soil. Do this with a moisture meter or with your fingers. If the soil is more than 1 inch dry, you need to water the tomato. Don’t be fooled by the advice to stick to a schedule, the weather is constantly changing and the tomato’s watering needs change accordingly. The exception to this is tomatoes growing in the greenhouse.
When watering, moisten not just one inch of soil that has dried out. Water generously all the soil around the roots. The water should soak into the depth of the entire root system, but don’t make a bog around the tomato. After watering, the soil should be moist but not wet.
The second problem is overwatering. If you water too often or with too much water, the roots can start to rot. As a result, the water supply to the leaves will be interrupted and the leaves may curl down. This is very similar to underwatering because in both cases, the roots are not doing their job.
To remedy this, water the tomato as I recommended above. If it hasn’t fructified yet, you can transplant it into clean, well-drained soil, removing any rotten tissue. Or water it with fungicide against root rot.
Lack of nutrients
Tomato leaves curling because of improper fertilization.
Fertilizer plays an exceptional role in the formation of large and juicy tomato fruits. Regular soil is not too nutritious for growing tomatoes so fertilizer is definitely needed. But improper fertilization can lead to problems.
The first thing to note here is the excessive amount of nitrogen in the soil. This often happens when using fertilizers with a high proportion of nitrogen about other micronutrients. As a result, the leaves start to grow more intensively and curl down.
In most cases, nothing bad will happen, but the fruit may not be large enough. Over time, the rain will wash away the nitrogen and everything will go back to normal. To avoid such problems in the future, always use a fertilizer with equal parts nitrogen, phosphorus, and potassium.
The second is a general lack of soil nutrition. In this case, the tomato leaves may not only curl but also turn yellow. In addition, the plant will develop noticeably slower and fruit poorly.
To solve this problem, add good quality fresh compost to the soil. One bucket under each bush is enough to improve the condition of your tomatoes. Spread some of the compost on the surface around the plant to prevent the soil from drying out quickly and overheating.
Next, use a multi-purpose fertilizer with a balanced NPK formula, for instance, 10-10-10. Slow-release pellets work noticeably more effective than other types of fertilizer. It is best to fertilize in the spring before the fruits begin to form.
Herbicide damage
Tomato leaves curling because of herbicide damage.
Another common cause of tomato leaf curl is herbicides. Perhaps you wanted to get rid of weeds in your beds and accidentally sprayed the tomato. This can happen if there are a lot of tomatoes and you can’t always be careful enough with herbicides.
In this case, the leaves on which the herbicide hit will curl inward and shrivel. Their color becomes pale and then turns yellow. The peculiarity of such curling is that not all leaves are curled but only the damaged part.
If the number of damaged leaves is not high, the plant will resume after a while. However, I would not recommend eating the fruits of such a tomato. The curled leaves will shrivel up and fall off.
If severely damaged, the plant will shrivel up completely. You need to throw it in the garbage, do not make compost out of it. Herbicides can accumulate in plant tissue and then damage other plants.
There is no solution to this problem. The tomato will either survive or die, depending on the extent of the damage. In the future, be extra vigilant when working with herbicides near tomatoes and other plants.
Tomato yellow leaf curl virus
Tomato leaves curled by TYLCV
Viruses are a real disaster for growers because they are almost impossible to control. In some agricultural regions, viruses cause enormous damage.
The most common virus among tomatoes is the Tomato yellow leaf curl virus. Symptoms of this disease show upward curling of the leaves. Usually, the leaf deformation is very severe and noticeably different from other causes of curl.
Also, part of the leaf turns yellow. It is a bit like chlorosis, except that in chlorosis, the leaves are almost not curled.
The Tomato yellow leaf curl virus is spread by insects, namely the whitefly. Other insects hardly ever spread the disease. It is also possible that the virus can be transmitted by generative means.
There are no effective treatments for this virus. The control method is to prevent insect damage to tomatoes.
If you see one of your tomatoes turning yellow and the leaves curling (as in the photo), you should get rid of it. Don’t compost or leave it in your yard, instead, throw the plant as far away as possible or burn it.
The next thing to do is to spray all your plants, including tomatoes, with horticultural oil. This will drastically reduce the number of insects and therefore reduce the risk of spreading the virus.
Pest infestation
Tomato leaves curling because of aphids.
Last on the list of potential leaf curlers are insects. This is the last but not the least common cause of damage and deformation of tomato leaves.
There is a legion of insect pests of tomatoes, but the most common cause of leaf curl is aphids. They are small sucking insects that are gray or greenish in color. They are usually located at the bottom of the leaf.
Their activity causes the leaves to curl upward. Also, tubercles may appear on the leaves where the aphids are most dense. Ants are a huge contributor to the spread of aphids.
If your tomato leaves are deformed, look for aphids. These insects are easy to see with the naked eye.
To get rid of these pests you need to spray your tomato with horticultural oil. This is usually enough to make the aphids go away. If it is very widespread, you may need to spray again.
Do not use pesticides against aphids, as this will make the fruit unfit for consumption.