Why do the leaves of tomatoes in a greenhouse turn yellow and dry?

Tomato seeds were brought to Europe a long time ago, but at first these fruits were considered poisonous, then they could not find a way to grow subtropical tomatoes in a temperate climate. Today there are many varieties of tomatoes that can withstand changing weather, low temperatures and other vagaries of nature. But, nevertheless, the highest yields can only be obtained as a result of greenhouse cultivation: here a person controls the microclimate, and the tomatoes feel comfortable.

But even in such conditions, problems may lie in wait for the gardener, and one of the most common is yellowing of the leaves of greenhouse tomatoes. Why do tomato leaves turn yellow in a greenhouse, and what to do in such cases - let's try to figure it out.

Why do the leaves of tomatoes in a greenhouse turn yellow?

Tomatoes in a greenhouse are undoubtedly more protected from external influences; here they are not afraid of night frosts, heavy rains or unbearable heat. The gardener’s task is to maintain an optimal microclimate inside his greenhouse.

Tomatoes love this “weather”:

• air temperature within 23-30 degrees;
• constant humidity at 60-70%;
• regular watering;
• ample sunshine, but not the scorching midday heat.

To tomato seedlings felt comfortable in greenhouse conditions, she needs to provide all the above conditions. And in addition, constantly monitor the condition of the plants and identify problems in the early stages.

Yellowness on tomato foliage can appear due to a number of reasons, such as:

1. Violation of temperature and humidity conditions in the greenhouse.
2. Incorrect watering.
3. Damage to the root system.
4. Imbalance of microelements in the soil.
5. Viral or fungal infections.

In each of these cases, the leaves of the tomatoes turn yellow, but this manifests itself in different ways. The methods of “treatment” also differ.

Violation of the microclimate inside the greenhouse

When equipping a greenhouse on his site, a gardener must remember some rules:

• It is better not to build a greenhouse in a place that is open on all sides, but to choose a site that will be shaded by trees or outbuildings at lunchtime. If the sun constantly shines on the greenhouse with tomatoes, it will not be possible to maintain the temperature inside it at around 30 degrees - the thermometer readings can exceed 45 degrees Celsius. In such conditions, the tomatoes will turn yellow, dry out, and drop ovaries and flowers.
• The soil in the greenhouse must be changed regularly, it is better to do this before the start of each season. It is in the soil that the larvae of insect pests lurk; infectious agents or fungal spores may be present for several years. If it is not possible to replace all the soil from the greenhouse, you can disinfect it a couple of days before planting the seedlings by pouring boiling water or a solution of potassium permanganate.
• Every spring, the greenhouse must be disinfected, this applies to both walls and wooden pallets. Garden tools also need to be treated with antiseptics.
• For planting, you should choose only tomato seeds collected from healthy plants. In any case, it is better to keep the seeds in a weak solution of potassium permanganate before planting.
• To reduce humidity, it is necessary to open the windows and doors of the greenhouse - thanks to ventilation, excess moisture will quickly evaporate from the walls of the greenhouse and from the ground.
• If there is not enough moisture in the greenhouse and the air is too dry, the tomato leaves may also begin to turn yellow. In this case, you can place small open containers of water inside or use a humidifier.
• The temperature in the greenhouse, however, greatly depends on the climate outside. You can fully control the thermometer readings only in a heated greenhouse. In other cases, it is necessary to regulate the microclimate by ventilation, opening doors, and humidifying the air.

Tomato root damage

The root system of tomatoes is well developed; the central root of tomatoes can go underground to a depth of 150 cm, so many varieties tolerate drought and irregular watering well. But Most of the lateral roots, however, are only 15-20 cm from the surface of the ground, so tomatoes need regular watering.

The healthy appearance of tomatoes directly depends on the integrity and condition of the root system, because roots are the organ that supplies plants with water and nutrients. If tomato leaves turn yellow And dry up, this may indicate problems with the root system.

Tomato roots can be damaged in several cases:

• due to growing seedlings in cups or boxes that are too tight. In this case, the roots of the tomato are curled into a tight ball, it is very difficult to straighten and untangle them, so the roots are severely damaged when transplanted into the greenhouse. As a result, the adaptation of tomatoes in a new place worsens, their leaves begin to dry out and turn yellow.
• The same effect can be obtained if you keep tomato seedlings indoors - the root system will become too developed, it will be difficult for the plants to adapt to the new place, it will begin to turn yellow and lose foliage.
• Pests can also spoil the roots. The most dangerous for tomatoes are mole crickets and wireworms. If a gardener notices yellowing of tomato seedlings after transplanting into a greenhouse, you need to treat the soil with suitable insecticides.

Watering schedule

The appearance of yellowed leaves on tomatoes may indicate either a lack of moisture in the soil or an excess of it. How to figure out: do tomatoes have a lot of water or not enough? This is very simple to do - you need to carefully examine the ground and the plants themselves.

If tomatoes are experiencing moisture deficiency, the picture will be like this:

• the soil around the tomatoes is dry and cracked;
• tomato stems are flaccid with low turgor;
• the leaves are lifeless, hanging like rags;
• All the leaves on the bushes can turn yellow at once.

Seeing such a situation in their plot, gardeners often rush to help the tomatoes and pour them with plenty of water.This should not be done, especially if the tomatoes are at the fruit ripening stage. Due to the large amount of moisture, the tomatoes will crack and the harvest will be spoiled.

Tomato leaves also turn yellow when they lack water. But in this case:

• the ground does not look dry, on the contrary, it may silt or become covered with moss;
• Tomato stems are elastic and break easily;
• Signs of fungal infections appear on plants.

You can prevent problems with yellowed leaves if you water tomato seedlings correctly:

1. Only in the morning or evening. Sunburn through water droplets also manifests itself as yellowing of the leaves.
2. Use settled warm water.
3. Avoid getting water on the leaves and stems of the tomato to avoid causing fungal infections.
4. Pour water only at the roots or install a drip irrigation system in the greenhouse.
5. Water the tomatoes rarely, but generously. The ideal watering schedule for tomatoes is twice a week.

Eating problems

Both a deficiency and an excess of microelements in the soil can cause yellowing of tomato leaves.. Therefore, it is very important to follow the fertilizer application schedule and constantly monitor the condition of the seedlings.

You can find out which substance is imbalanced by the appearance of tomato leaves:

1. In the greenhouse, the leaves turn yellow only in the lower part of the bush, the young leaves are green and look quite healthy, the plant itself is lethargic, stunted with small leaves, without flowers and ovaries - tomatoes lack nitrogen. Nitrophoska or other complexes containing nitrogen will help correct the situation. You can also fertilize tomatoes with slurry (1:10 with water) or mullein. A distinctive feature of leaves during a period of nitrogen starvation is that green veins are preserved.
2. To know about potassium deficiency you can look at the small light dots that appear on all the leaves of the tomato bush. Over time, these spots grow until they merge into a large bright spot. It’s easy to help plants: fertilize the soil with potassium-containing preparations.
3. That tomatoes lack manganese, will tell the yellowing of the upper young leaves, gradually descending downwards. Brown spots can occur due to excessive liming of the soil, as a result of which the amount of manganese is significantly reduced. A solution of slurry and wood ash or fresh mullein can help tomatoes.
   
4. If there is not enough sulfur in the ground, the tomato leaves not only turn yellow, but also become denser.
5. Copper deficiency manifests itself in yellowing of only the lower old leaves.
6. When tomatoes lack phosphorus, the tops of their leaves turn yellow and quickly die. If the top of the leaf is dry, you need to feed the tomatoes with superphosphate.
   

Diseases and infections

Maybe, The most dangerous thing for tomatoes is infections, which also quite often manifest themselves as yellowing of the leaves. However, this is not the worst thing - on the leaves disease does not stop, it destroys the entire plant: from the top to the roots.

Today, several dozen infections are known that can affect tomatoes. The most common and dangerous of them are fusarium and late blight, the first sign of which is leaves that have turned yellow.

Fusarium, for example, it appears suddenly and is manifested by a violation of the color and elasticity of tomato leaves. The spores of this fungal infection can be stored for several years in the soil, on tomato seeds, on gardening tools or in the structures of the greenhouse itself.

It is very difficult to combat Fusarium wilt; often this disease destroys the entire tomato crop in a matter of days. If the first signs of fusarium are noticed, it is necessary to treat the bushes with Trichodermin or Previkur.

Both young bushes and mature plants with ripening fruits can get sick. First, the fungus damages the roots, which is why yellowing of the foliage can be observed. Then the disease spreads along the stem, enters the fruits and ovaries - the entire bush eventually dies.

Fusarium wilt can be prevented if you disinfect the soil in the greenhouse, all structures, tools, and treat the seeds before sowing for seedlings.

Late blight no less dangerous and very famous among gardeners. Its appearance is also facilitated by microclimate disturbances, high humidity, heat or, conversely, too low an air temperature.

If in most cases the lower leaves of a tomato turn yellow, then when tomatoes are infected with late blight, the tops of the shoots and ovaries first acquire a brown tint and begin to dry out.

Drip irrigation and preventive treatment of plants with antifungal drugs will help prevent late blight infection of tomatoes. When the bushes are already sick, you can treat them with Bordeaux mixture, but the treatment will have to be repeated regularly until harvest.

Results

Capricious tomatoes can have many problems, but almost all of them manifest themselves in the same way - yellowing leaves or the appearance of strange spots. To solve the problem, you need to find out what the plant doesn’t like, what leads to its wilting, and then take some measures.

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