How to protect tomatoes from heat in a greenhouse

To quickly harvest tomatoes, greenhouses or hotbeds are often used. These conditions facilitate the growing process, but require gardeners to maintain a favorable microclimate within the shelter, regulating humidity and temperature. Sudden fluctuations or deviations from these values ​​slow plant growth or even lead to plant death. Heat in a greenhouse is especially dangerous for tomatoes. Therefore, it is important to protect plants from overheating.

The dangers of overheating for tomatoes

Tomatoes were brought to Europe from South America, so these plants thrive in high temperatures. However, this doesn't mean you shouldn't monitor the greenhouse temperature. The minimum temperature for active tomato growth is 10 degrees Celsius (50 degrees Fahrenheit). At lower temperatures, plants are unable to extract and absorb nutrients.

For tomato plants to thrive, it's important to maintain soil temperatures between 14 and 25 degrees Celsius. The air temperature should also remain constant. Sudden changes in daytime and nighttime temperatures are detrimental to this crop. To ensure these conditions are met, ventilation is provided during the day.

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To control the temperature, thermostats are installed at different levels inside the greenhouse or hothouse:

• at ground level;
• under the roof of the greenhouse;
• at a height of 1.2 m.

Extremely high temperatures trigger shock in plants. They stop growing and developing, devoting all their energy to respiration. Overheating reduces the rate of photosynthesis and deprives pollen of its ability to pollinate. As a result, tomato ovaries fail to form.

The green parts of tomato plants are scorched by high temperatures. The leaves become limp and pale, drooping lifelessly. If the root system and stems are damaged by overheating, the seedlings die. If individual leaves are scorched, they are removed. If large amounts of damaged foliage are removed in several stages to prevent further stress on the plant. After the affected plants recover, fruiting is delayed for several weeks. Therefore, it is best to avoid this situation.

Protecting tomatoes in a greenhouse from overheating

The negative impact of overheating on the growth and development of greenhouse tomatoes becomes noticeable very quickly. After just five hours of exposure to high temperatures, the foliage wilts and loses its normal color. Flowers and ovaries then wilt and begin to fall off. Protecting plants from overheating should begin immediately after the foliage wilts.

Moisture retention

If the air in the greenhouse reaches its maximum temperature, it's important to maintain high soil moisture levels to protect the plants. Keep in mind, however, that tomatoes do not tolerate frequent and heavy irrigation. This type of watering erodes the surface soil, exposing the root system and washing away nutrients essential for plant growth.

A gardener's primary goal for plant survival is to reduce moisture evaporation. To achieve this, the soil is mulched with mown grass or pre-harvested hay. Thick paper or covering material purchased at a gardening store are suitable for mulch.

To retain moisture in the soil, loosening is used:

1. The bushes are earthed up to a maximum depth of 5 cm to avoid disturbing the root system. This will preserve moisture in the air and soil.
2. During hot periods, loosening helps protect the roots from overheating.
3. This procedure stimulates lateral branching of the root system, which improves the quality of the future harvest.

Shading

Gardeners use available tools to create shade. If there's space around the greenhouse, plants can be planted. However, they shouldn't be too tall to block sunlight. It's recommended to plan the greenhouse's location in advance and initially build it near existing suitable plantings. Avoid placing the greenhouse near fruit trees, as they create dense shade and block sunlight. A broken branch or fallen fruit can damage the greenhouse covering.

Another way to shade plants in a greenhouse or hothouse is to spray the roof with a chalk solution. The moisture evaporates quickly, leaving a thin layer of chalk on the surface, protecting the plants from the scorching heat. The chalk dust is easily washed off. It's best not to use paint for this purpose, as it's difficult to remove. You can also use cut tree branches as cover, spreading them on the roof of the greenhouse.

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Large structures can be conveniently shaded with special netting. Depending on their density, such coverings filter between 25% and 75% of sunlight. A special, easily washable paint applied to the greenhouse roof is also used for shading. Curtains with light sensors are a convenient option. When the temperature rises above a preset level, they automatically close the greenhouse.

Ventilation

The easiest way to regulate the temperature inside a greenhouse is through periodic ventilation. In the simplest greenhouses with a polyethylene covering, a side vent is left open for this purpose. It is opened for ventilation during peak temperatures. This prevents the plants from overheating. If the greenhouse is large, several side vents are installed at regular intervals. This prevents stale, hot air from stagnating inside the structure.

Natural ventilation is not without its drawbacks:

• the open sash allows insects and birds to fly inside;
• Ventilation does not protect plants from ultraviolet radiation.

In large greenhouses where plants are grown commercially, forced ventilation is convenient. For this purpose, exhaust hoods and fans are installed, and the room is equipped with temperature sensors. These sensors activate forced ventilation when needed. For a home greenhouse, installing such a system is an unnecessary expense. In this case, standard vents are sufficient.

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Maintaining the correct temperature is essential for a high yield of greenhouse tomatoes. Before planting seedlings, ensure adequate ventilation and protect the plants from the sun.