What Temperature Kills Tomato Plants? [Solved]

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What temperature kills tomato plants? Like every year, or maybe for the first year, you want to plant some tomatoes for the growing season. You want to plant them early so the growing season is as long as possible.

The problem is that you are unsure what is too cold for tomato plants.

I personally have had this problem every year. I start and grow my tomatoes indoors under a grow light. I always try to find the ideal time to put the tomatoes outdoors once the temperatures allow. As I live in Switzerland, that can get quite tricky. On the other hand, it can also get too hot here in summer, negatively affecting the fruiting and harvest.

This article will discuss the lowest and highest temperatures that kill tomato plants.

Takeaways

What Temperature Kills Tomato Plants?

Tomato plants die when temperatures get below 32 degrees Fahrenheit (0 degrees Celsius). Temperatures above 85 degrees Fahrenheit (30 degrees Celsius) affect fruit ripening, pollination, leaves curl, and the plant focuses on survival rather than growth, development, or yielding.

 

Ideal Temperature for the Growth and Development of Tomato Plants

The ideal temperature for tomato plants is between 70 and 85 degrees Fahrenheit  (21-30 degrees Celsius).

Tomato plants are warm-season plants that grow at constant temperatures.

 Read more about Tomatoes.

What is Too Cold for Tomato Plants

Temperatures below 50 degrees Fahrenheit (10 degrees Celsius) are too cold for tomato plants.

Tomato seedlings cannot germinate below this temperature, and the process takes longer at temperatures below 70 degrees Fahrenheit (21 degrees Celsius).

Young tomato plants become stunted below 50 degrees Fahrenheit as mature plants fail to produce fruit at this temperature.

Temperatures below the 32-degree Fahrenheit mark (0 degrees Celsius) cause frost, eventually killing the tomato plant and the fruits.

Tomato plants survive up to a temperature of 33 degrees Fahrenheit (0.5 degrees Celsius), though they do not yield or grow at this point. 

Recovery from the cold injury depends on how low the temperatures drop and the extent of the damage.

Tomato plants hit by frost may have irrecoverable damage because they have frozen tissue, and their cells freeze and rupture.

This damage is identified by checking for wilting, black or shapeless plants and fruits.

If hit by frost, allow the plant to defrost on its own. After a few hours, check on the plant to see its damage.

How to Prevent Cold Temperatures From Killing Your Tomato Plant

To prevent the cold weather from killing or damaging your tomato plants:

1. Always Grow the Plants During the Right Season

Grow the plants after the last frost date, when summer begins. When the growing seasons are short, grow the seedlings indoors and transplant them outdoors after the frost disappears.

Grow tomato varieties that are tolerant to a bit of cold weather. Some varieties of tomato plants, such as the Anna Russian variety and Azoychka variety, tolerate a little frost.

2. Cover the Tomato Plants

Cover the plants, especially at night, when certain that temperatures will drop below tolerable temperature at night.

Water the plant before covering it because a hydrated plant has a higher potential to survive cold than a dehydrated one. 

The covering could be a simple garbage bag placed on the plants. Use posts to keep the plastic bag from contact with the tomato plant.

What is too hot for Tomato Plants

High temperatures above the recommended 85 degrees Fahrenheit during the day and above 75 degrees Fahrenheit (24 degrees Celsius) at night could harm the tomato plant.

This temperature leads to less flower pollination. That reduces fruit production. 

 

How to Prevent the Death of Tomato Plants During Hot Weather

The following are tips on how to stop high temperatures from killing your tomato plant.

1. Select the Appropriate Variety for your Region’s Climate

Varieties such as Heatmaster, Solar Fire, Summer Set, and Phoenix are tolerant to very high temperatures and are a good choice for areas where temperatures are constantly high.

Growing varieties with short ripening periods in the growing season would be ideal for ripening before the high-temperature seasons set in.

2. Plant in the Right Place

The tomato plants should be grown where they receive the morning sun and indirect sun during the midday when the sun is scorching.

Provide shade for the plant at this time if the place doesn’t have natural shade.

3. Shade the Tomato Plant

Shading tomato plants at critical pollination times (10:00 AM and 2:00 PM) produces good yields, especially when the eastern part of the structure is left open to expose the plants to the morning sun.

The shade is made from wood that makes the structure’s frame and a drape shade cloth.

4. Add Mulch

Mulch such as cotton husks, straws, shredded barks, and chopped leaves are placed 2 to 3 inches (5.0-7.5cm) around the tomato plant to keep the soil moist.

5. Water the Plants

High temperature above 90 degrees Fahrenheit (32 degrees Celsius) causes adaptation of the leaves and fruits for survival.

Watering helps prevent the falling of flowers and cracking of fruits. 

6. Harvest Tomatoes Early

Harvesting should be done before the intense heat sets in, and ripening can continue indoors. This is in the late summer months. You can harvest tomatoes at the stage where they are half pink and half green.

This stage is called the breaker stage.

Temperature Effects on Plants

Temperature plays a crucial role in plant health. Excessively high or low temperatures can injure plants. The following are the effects of temperature on plants:

• Warmth is one of the four requirements for germination in plants. The germination rate increases with temperature rise to a specific point upon which germination begins to decline. 
• Different plants have different germination temperatures. Cold-season vegetables such as lettuce and marigolds germinate between 55-70 degrees Fahrenheit (13-21 degrees Celsius). 

• High temperatures increase photosynthesis and respiration. When the temperatures are higher above the optimum levels, there will be an imbalance in the two processes.  
• Low temperatures affect plant growth processes such as cell division, photosynthesis, water transport, and yielding. 
• When the temperature is extremely low, the plant develops chill injury. This can kill or severely injure a plant
• Freeze injury is when water in intracellular regions freezes due to ice, leading to cell dehydration or suffocation when thick snow covers the plant surface or soil surface to prevent the entry of oxygen.

 

Frequently Asked Questions

 

Can tomatoes thrive at 35 degrees Fahrenheit (2 degrees Celsius)?

Tomatoes survive at 35 degrees Fahrenheit (2 degrees Celsius). Survival means the growth and development, flowering and yielding, is halted. Tomato plants wilt and die in temperatures below 32 degrees Fahrenheit (0 degrees Celsius).

How Can I Protect Tomatoes During Cold Nights?

Cover the tomato plants with plastic bags on nights when temperatures are as low as 30-40 degrees Fahrenheit (-1-4 degrees Celsius). The cover can be as simple as garbage bags, clear plastic, or tarps. Use frost protection regularly when the cold pattern extends.

Will Extreme Heat Kill Tomato Plants?

Extreme temperatures are less likely to kill tomato plants, especially when watered frequently. Shading also helps prevent scalding on tomato fruits. Tomato blossoms are most affected by hot weather and are more protected by shading. 

Conclusion

Although tomato plants are quite resistant to cold and hot temperatures, avoid the extremes. Hot temperatures above 85 degrees Fahrenheit (30 degrees Celsius) negatively affect the plant and the tomato harvest. Freezing temperatures below 32 degrees Fahrenheit (0 degrees Celsius) will kill tomatoes.