With very little effort, a gardener can add 10 to 15 days to the vegetable growing season. Planting cold susceptible crops early and protecting them from late cold snaps using hot caps, jars, plastic jugs, cardboard boxes or plastic coverings will help extend the gardening season somewhat. But perhaps the best method is to use a cold frame.

Cold frames have been called a poor man's greenhouse. A cold frame can be simply defined as a box which gives plants protection from wind, rain and cold and is not artificially heated. If artificial heat is supplied, then the cold frame becomes a hot bed.

Using a cold frame allows you to get an early start on the spring gardening season. Although you can start tomatoes, cucumbers and other seedlings in a sunny area in the house, these seedlings often become leggy and weak from growing too fast. If moved outside, these plants may not be able to make the sudden adjustment to fluctuating day and night temperatures and poor growth results. The best solution is to germinate the seeds inside and as soon as the seedlings have formed a set of true leaves, move the plants to a protected area outdoors where they can gradually become acclimated to outside conditions. Although cold frames are usually used to get an early start on spring gardening season, during winter they can be used to protect crops such as lettuce, radishes, beets and carrots from possible damaging cold weather.

The cold frame should be located on a well-drained site and oriented to the south to take advantage of the warming rays of the sun. Some type of protection on the north side such as a fence or wall will help protect the cold frame from northerly winds and can also be utilized to reflect heat and light to the cold frame.

Cold frames can be built in many different shapes and sizes. A convenient size is 3- 6 feet wide with a 12-inch front and an 18-inch back. The sides can be made of plywood and the top constructed of light lumber or old window or glass door frames. The wood should be treated to prevent rot with a preservative of some type which is nontoxic to plants. It is also a good idea to paint the inside either white or silver to reflect more light to the plants. The top should be attached to the high side of the cold frame with hinges to allow it to be opened and closed.

Cold frames are usually sunk 4- to 6-inches into the soil to provide adequate protection from extremes in weather conditions. Soil can also be banked up around the cold frame to provide added insulation. Although not absolutely necessary, it is often advantageous to remove 4- to 6-inches of soil from beneath the cold frame and replace it with a layer of gravel or sand. If seedlings are to be grown directly in the cold frame rather than in some type of planting flat or container, 2 inches of gravel and 4 inches of a good, fertile topsoil or soil mix should be applied to the bottom of the cold frame.

Operation of the cold frame is relatively simple. To help maintain optimum growing temperatures, equip the cold frame with a thermometer. Use a thermometer to determine whether or not the top or "sash" of the cold frame should be opened to allow ventilation. When the temperature reads above optimum growing conditions, open the sash and permit air circulation to reduce the temperature. When the sun goes down or when temperatures start to drop, close the sash to retain the heat absorbed from the sun by the soil.

The secret to successful plant growing in a cold frame is to be sure to give the plants plenty of ventilation, but do not open the cold frame directly into a gusty wind. Optimum growing temperatures for seedlings of most, cold hardy plants range from 50 to 70 degrees F. When the temperature is cold outside and the sun is shining, you might have to raise the top to keep the plants from overheating. It can get over 90 degrees F. outside. On extremely cold nights or during extended cold periods, the cold frame may need some extra protection by covering it with a quilt or blanket. By the same token, if the sun is bright and temperatures are high, you may need some shading to keep the plants from burning.

If you are a serious gardener, give some thought to building a cold frame to extend your garden season. You may find that a sheet of plywood and an old window frame may be your best garden investment ever.

IMPORTANT DATES:

February 17 - East Texas Commercial Fruit and Vegetable Conference, Rose Garden Center, Tyler, 8:00 a.m., 4 CEUs, $20.00/person

March 7 - Wildlife Tax Valuation Workshop, Gus Engeling Wildlife Management Area, Tennessee Colony, 8:30 a.m., $12.00/ person. For more information contact Wes Littrell or Jennifer Ganter at 903-928-2251.

Rick Hirsch is the Henderson County Extension Agent-Agriculture for Texas AgriLife Extension Service. Visit our web page at http:// henderson-co.tamu.edu