Frost and Freeze Protection for Vegetables

— Written By Chris Gunter and last updated by

The clear skies and calm winds predicted for this weekend will likely lead to freeze or frost conditions in North Carolina. Sunday morning, May 10, 2020,  the temperature is predicted to drop into the 30s across the state and even lower in  low-lying rural areas. Not only are daily low temperature records likely to be broken, but this will tie the latest spring freeze for Raleigh, May 10th (31 ºF) and set a new record for Greensboro where the current record is May 8th  (32 ºF).

If water within or between the plant cells freeze, this can result in damage to plant tissue. Cold damage results from the actual temperature and the duration of that temperature. Some plants are more resistant to freeze damage.

Frost on Kale

Frost occurs at temperatures from 31-33 ºF and will result in damage or destruction of the foliage of warm season plants like beans, corn, cantaloupe, cucumbers, eggplant, okra, southern peas, peppers, potatoes, sweet corn, sweetpotatoes, squash, tomatoes, and watermelon.

Temperatures below 26-31 ºF, cause a hard frost or freeze. Some cool season crops will tolerate a temperature dip to these temperatures for a limited period of time. These include broccoli, cabbage, cauliflower, chard, English peas, lettuce, mustard, onion, radishes and turnips. The plant may survive, however, the foliage may be damaged resulting in a lower yield.

Some cool season crops like Brussels sprouts, beets, collards, kale, parsley, and spinach will survive even If the temperature drops below 26 ºF for an extended period of time.

See Charlotte Glen’s post about seeds and seedlings surviving cold temperatures.

To protect your plants:

  • Ensure they are well watered.  Drought stress are more vulnerable to cold damage. In addition, moist soil retains heat longer and releases it slowly during the cold event.
  • Do not cultivate the soil just prior to a frost or freeze since cultivation can damage plant roots increasing plant stress, result in loss of soil moisture, and allow cool air to penetrate deeper into the ground. 
  • Cover plants
      • Frost cloth – rated by the degrees of protection it provides
      • Waxed paper cups – for overnight protection of small transplants
      • Carefully monitor the temperatures under the covers and remove before temperatures rise too high.
  • In extreme cases, newly transplanted tomatoes and peppers, can be carefully dug up and brought inside to avoid the freeze and then replanted when the danger is past.

Select a strategy and prepare ahead of time to minimize frost damage.

This article originally written for vegetable growers, has been edited by Lucy Bradley for home gardeners.

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