Question: With the first frost coming soon, will you tell me which vegetables will survive unprotected in the garden?
-T.M., Philadelphia, PA
Answer: Fall, with its cooler temperatures and more abundant moisture, offers excellent growing conditions for many vegetables. Yes, beans, cucumbers, eggplant, musk melon, okra, peppers, pumpkins, squash, sweet corn, sweet potato, and tomatoes will all be damaged by even a light frost, but many other crops will survive. These can best be divided into two categories: semi-hardy and hardy.
Semi-hardy vegetables are those which can survive repeated light frosts in the 30-32 F range. These include beets, Chinese cabbage, cauliflower, celery, collards, green onions, potatoes, Bibb and leaf lettuce, mustard, parsnips, radishes, salsify, spinach, and Swiss chard. The flavor of some of these, such as collards and parsnips, is, in fact, much improved by exposure to a spell of below-freezing temperature.
Hardy vegetables are those that can survive temperatures as low as 20 °F before finally being killed. These vegetables include cabbage, broccoli, brussels sprouts, carrots, kale, leeks, rutabagas, and turnips. Upon thawing out, these hardy vegetables will continue to grow between freezes.
Remember, too, that even when the tops of such vegetables as carrots and turnips are killed by cold, the roots will remain in good condition if the plants are mulched with a generous layer of insulating material, such as hay or leaves. This will prevent the ground itself from freezing and allow you to harvest the fresh roots as you wish during the winter. You may, however, find that voles discover and enjoy your cache of overwintering produce first.