What Temperatures Can Tomatoes Tolerate?

Last updated on October 23rd, 2023 at 08:30 pm

Tomato plants, in addition to the appropriate location and proper care, especially need the optimal temperature to grow and thrive. Depending on which stage of the ripening process the plant is in, it has different temperature requirements.

Germination and growing

Tomato plants are relatively simple to raise yourself with the necessary know-how and equipment. In order for the seeds to germinate, the ideal conditions must be met. In addition to the location and the appropriate growing soil, the temperature is a key factor in achieving successful germination. Basically, the following guideline values apply to germination with regard to the degree of warmth:

• the ideal germination temperature is between 20-24 degrees.
• after germination the temperature can be lowered again
• the ideal temperature afterwards is around 18 degrees

Hardening off

Hardening off of the young plants is an essential part of tomato care, because here they are slowly familiarized with the outdoor conditions. Basically, the young plants are hardened off from about April to the end of May, whereby the final time depends on the one hand on the weather conditions and on the selected location. As a rule, the following guidelines apply with regard to temperatures during hardening off:

• the night temperature should no longer fall below 10 degrees
• if it does, the plants should be brought indoors to a warm place.
• Ideally, the temperature should be at least 8 degrees Celsius.

Planting out

After the young plants have been gently hardened off, they can be planted out. In principle, this is done only after the Ice Saints, as the probability of frost at this time is already much lower. Before the tomatoes take their permanent location, make sure that the following temperatures can be guaranteed:

• the ideal soil temperature is about 13-15 degrees.
• in the vegetable patch, planting is possible from 20 May onwards.
• in the greenhouse, planting is possible from the middle / end of April.

During ripening

Sun-loving tomatoes prefer a particularly warm as well as sunny location. Tomato plants thrive best at temperatures of about 18-25 degrees. In the summer months, the required conditions can usually be guaranteed, but from late summer or autumn, however, there may be drastic temperature fluctuations. If it gets too cold, this can affect the health of the plants as well as the harvest. Therefore, care should be taken with the following temperatures:

• Daytime temperatures at about 15 degrees
• short-term temperature drop is not a problem for the tomatoes
• long-term daytime temperature of about 15 degrees, however, harmful
• especially if the night temperature is about 10 degrees
• this can lead to malformed or even missing fruits

• temperatures below 13 degrees
• affects the pollen and its viability
• complete pollination no longer takes place

• Temperatures below 10 degrees
• duration longer than 14 days leads to damage to the tomatoes
• in addition, fertilization does not take place

• temperatures below 5 degrees
• can lead to cold damage after only 6 to 8 days
• tissue is weakened and leads to cellular dysfunctions
• plant growth is disturbed and root development is prevented

• Temperatures below 0 degrees
• leads to frost damage
• can damage only a part of the plant
• but also the whole plant

Harvest and storage

The last harvest of tomatoes usually takes place in the fall, before temperatures drop below 5 degrees. Not ripened tomatoes require a slightly warmer storage place, whereas fresh, red fruits should preferably be stored in a cooler place. This is because temperatures that are too low can have a negative effect on the taste of the tomatoes and accelerate the rotting process. In order to store the fruit optimally, the following temperatures have proven to be effective:

• Temperatures between 12-16 degrees.
• truss tomatoes can be stored at about 13-18 degrees
• However, do not store tomatoes in the refrigerator
• because it is too cold there!

Allow tomatoes to ripen

Often in the fall you will find unripe fruits on the plants, which can basically ripen on the mother plant, as long as there is no danger of frost. Likewise, it is possible to let the picked tomatoes ripen indoors. Depending on which method is used for post-ripening, different ideal temperatures apply. However, as a general rule, the less ripe the fruit, the warmer it should be stored.

Outdoors on the mother plant

• if the temperature at night falls below 0 degrees, then bring the fruit into the warm place
• if it is colder than 12 degrees, the plants must be warmed up additionally
• for example with a warming foil

Picked tomatoes

• the optimal temperature is between 16-25 degrees
• the ideal temperature is 18-20 degrees

Wintering of tomatoes

Tomatoes in local regions are usually grown as annuals, but there are some tomato varieties that can tolerate winter and even become perennial. Apart from the selection of the tomato variety, the care, the location as well as the optimal temperature are decisive for the successful overwintering of the plants. The optimal thermal conditions also depend on the overwintering method:

• in the pot at a maximum of 15 degrees
• in the greenhouse ideally about 22-24 degrees.

Warming tomato plants

In local regions, temperature fluctuations can sometimes occur, with the cold in particular causing problems for the plants. Therefore, sometimes it is necessary to additionally protect the tomato plants from the cold. To provide the plants with sufficient heat, depending on the location – different methods have proven successful:

Warming in the greenhouse

• Manure heater
• Frost monitor
• Solar greenhouse heating

Cold protection in open field

• Tomato canopy
• Garden fleece
• Foil tunnel