Protecting Crops from Frost (firstfrost)

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Preparing for the First Frost

by Don Janssen, UNL Extension Educator

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The first killing frost need not mean the end of your garden harvest. Taking a few minutes to protect tender crops can extend the harvest well into October.

Some crops will be injured or killed by frost or freezing temperatures. Tender crops include tomatoes, peppers, cucumbers, squash and pumpkins, snap beans and eggplant. Other crops -- all the cabbage family crops, lettuce, spinach, chives, peas, carrots, parsnips and Jerusalem artichokes -- tolerate some frost. Brussels sprouts are actually better after a light frost or two, and the root crops can even overwinter in the garden.

When frost is forecast, concentrate your efforts on the warm-season crops that will be injured by cold temperatures.

Low-growing crops such as cucumbers and prostrate tomatoes are easy to cover with straw, newspapers or old bed sheets. Caged tomatoes and pepper and eggplant plants can be covered with paper grocery sacks or plastic trash bags.

The aim of covering plants is to trap heat from the soil in the air immediately around plants. It's important to uncover them the next morning, especially if you used plastic to fend off the frost. Plastic will trap the sun's heat the next day and plants may cook.

Another strategy -- the one most often used by commercial strawberry growers -- is to use overhead irrigation to sprinkle tender crops with water. Run the sprinkler from the time temperatures are near freezing until the ice melts. The heat given off by the water as it freezes on the plants keeps them from freezing.

Harvesting when frost threatens is another option. Whether you rush to pick your produce before frost depends largely on the crop, how you intend to use it and how soon you can use it if it does get frosted.

Winter squash and pumpkins intended for storage should be harvested before frost because frost will damage their rinds and shorten their storage life. If they do get frosted, harvest them within a day or two and cook, freeze or can them immediately.

Tomatoes that get frosted can be canned or frozen within a day or two, but they will deteriorate rapidly if you try to hold them. Green tomatoes picked before frost can be stored at 50 to 55 degrees F and ripened for weeks. Those picked after frost will not ripen or keep long, however.

Pepper plants turn black with frost and the fruits quickly turn mushy and rot. If you can't cover the plants, pick the peppers before frost.

Though bean plants are killed by frost or a hard freeze, the pods do not show damage right away. Pick and use or process them as soon as possible, however, for a quality product.

Summer squash plants wilt dramatically and fruits deteriorate quickly after freezing or frost. Pick summer squash before frost.

The cole crops -- broccoli, cabbage, Chinese cabbage, cauliflower and Brussels sprouts -- will tolerate quite a bit of frost. Though a really hard freeze will reduce the keeping quality of even these hardy vegetables, it's not necessary to rush to cover or harvest them when frost threatens.

This resource was added September 2008 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement