Issue: October 6th, 1997

Saving tomato plants from the frost?


I hope this isn't too late. For several years when the first frost arrived, my tomatoes plants were loaded with fruit. After frost, I just threw them into the compost. Is it possible to save these vegetables?


I usually get more questions than I can answer in this column and choose one or two to answer; your question gets moved to the head of the line. This is a very relevant question for right now.

While some parts of New Mexico may have already had a frost, most inhabited parts of the state have not yet suffered the end of the garden season. Warm season plants such as tomatoes, chiles, beans, squash, and others stop producing new fruit when the nights start getting cold, but there is still ripening fruit on the plant. To preserve this fruit until it is ready for harvest, you can employ several techniques. Yes, I am calling these vegetables fruits because the portion of these plants we harvest to eat is the part of the plant which produces the seeds. Botanically that is the definition of the fruit, even though when we eat it we consider it a vegetable, a culinary distinction.

If the fruit freezes, it should be discarded. Our purpose will be to prevent it from freezing. You can cover the sensitive plants with old bed sheets, blankets, or other opaque material in the evenings before a frost is expected. In fact, a heavy covering of leaves on the plants may protect the fruit as well. Whether covered by the leaves of the plants or your blankets, the purpose is to hold heat radiated from the soil around the fruit and prevent frost. The upper surface of the leaves or blanket may be covered with frost in the morning, but the heat held under the leaves or blanket prevents damage to the fruit.

If a hard freeze is predicted, these coverings may not be sufficient. In the case of a "hard freeze", lower temperatures and, often, convective heat loss are expected. Covering may work if the freeze is not severe, or if one or more light bulbs are placed under the covering with the plants to generate heat. However, it may be necessary to harvest the fruit and allow it to finish ripening indoors. At least there is no hazard of electrocution this way. Tomatoes which are full size and have already begun to show a lighter green color should ripen indoors. Some people uproot the plant and hang it from the rafters of a garage or basement. Whether individual tomatoes or tomatoes on hanging plants, you should have tomatoes ripening over a period of a few weeks. One year many years ago, I harvested over fifty green tomatoes and stored them on the kitchen counter. We ate red tomatoes until Christmas. By then, however, those ripening were not very flavorful and we had a cluttered kitchen for longer than my wife could tolerate. The smaller tomatoes which have not begun to lighten in color can be eaten as fried green tomatoes or preserved as green tomato chow-chow or as other types of tomato preserves. Directions for preparing these tomato products are available from your local Cooperative Extension Office and on the internet. Check the New Mexico State University, <a href="">College of Agriculture and Home Economics World Wide Web home page</a> for this and more information.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email:, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!