If you want to continue growing vegetables from fall into winter, a cold frame is a good option in areas with harsh winters. A cold frame is simply an enclosed space in your garden covered by a glass or plastic top. During the day, it captures the sun's warmth and maximizes it, acting as a sort of miniature greenhouse. The walls shelter plants growing inside from wind damage. If the weather becomes especially cold, insulate the top glass or plastic overnight and remove the insulation during the day.
Find out the average date of the first hard frost in your area. Consult the U.S. Department of Agriculture list of cooperative extension system offices in the Resource section. Then click the link for your county extension office to learn this information.
Coordinate the average maturity dates of the fall vegetables you want to grow with the average date of the first hard frost. Count backward to find out when you should sow the seeds so that they are fully mature before the frost.
Sow seeds directly into the soil inside the cold frame according to the dates you have figured and according to package instructions regarding planting depth. Different seeds have different depth requirements, which the packages will specify.
Water the soil using a gentle setting on your sprayer, such as mist, so you do not disturb the seeds or soil. Put the glass or plastic cover into place and let the seeds germinate.
Prop the cover open on days where the temperature exceeds 45 degrees Fahrenheit. Failure to do so can inadvertently cook your plants by providing them with too warm an environment.
Insulate your cold frame on nights when the temperature dips below freezing. Cover the glass with old blankets and/or straw to help retain some of the heat stored in the cold frame during the warmth of the day. Remove the insulation from the cold frame in the morning so the plants can get some sun and the frame can store more warmth.