Protecting Tomatoes from Frost and Freezing
Cold temperatures can damage or destroy your tomato plants. Protecting tomatoes from frost and freezing is important to having healthy crop – both at the beginning of the season and at the end.
The most important step to protecting tomatoes
The best step you can take to protect tomato plants from frost is to pay attention to the weather forecast. When you hear a frost or freeze warning, take appropriate steps to protect your plants.
What’s the difference between a freeze and a frost?
A freeze occurs when the temperature dips below 32ºF (0ºC). Usually a freeze affects an entire region and may last several days.
Temperatures associated with a freeze are lower than temperatures associated with a frost.
Surprisingly, tomatoes can survive a light freeze if it is not accompanied by frost, provided temperatures don’t dip below 28-30ºF.
A frost, on the other hand, is localized. Low temperatures may or may not reach freezing, but moisture must be in the picture for frost to develop.
A frost typically falls overnight but during the following day, temperatures warm.
How does frost develop?
- Frost requires clear skies and calm winds in order to accumulate.
- Heat radiates from the soil, leading surfaces to get colder.
- Moisture comes into contact with soil and plant surfaces.
- Moisture crystallizes on the tomato plant, destroying the plant cells when it melts. When damage is severe, the plant dies.
What is “black frost”?
In very dry, cold weather, it’s temperatures (not frost) that can damage plants. Cold temps darken leaves and stems. That’s why the condition is called “black frost.”
What to know about protecting tomatoes in a frost
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- Frost can occur when temperatures are as high as 40ºF. Moisture, rather than temperature, is the determining factor.
- Low-lying areas, where cold air settles, are more susceptible to frost. If your tomato patch is in a low area, pay special attention as temperature dip into the 40s.
- Tomatoes cannot withstand frost. When a frost warning is forecast for your area, choose from various types of frost protection to safeguard young plants in the spring and mature plants in the fall. Tunnel row covers, floating row covers, water barriers, individual plant covers
– even sheets, blankets, and plastic – can help save tomato plants from frost injury. (Find out more about different types of frost protection).
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