Even though winter is short in Alabama, it is still long enough and cold enough to kill the warm weather annuals and subtropical plants enjoyed during a long summer. A solution that comes and goes with the cold weather is a portable, 6-x 8-foot greenhouse to overwinter half-hardy, high-value plants.Although not heated, just the warmth that builds up during the day, coupled with the protection at night, lets it overwinter items that would certainly freeze if left in the garden. This provides a head start to many plants each spring because they are large, and it saves the expense of buying them again.Right now, our greenhouse holds a dracaena, citrus tree, bay tree, olive tree, European fan palm and assorted succulents. In addition, rosemary, thyme, and mint grow in the extra warmth, providing harvests through winter. Spinach and arugula in self-watering grow boxes provide greens for a salad each week. The Tinker Toy-like frame of the greenhouse assembles quickly. The pre-stitched, reinforced clear polyethylene cover fits snugly to the frame. There are doors on both ends that open and close with a heavy-duty zipper. It took about three hours to assemble it the first time, but now it takes about 30 minutes. When warm weather arrives in spring, the plastic of the greenhouse slips off the frame and can be folded and tightly rolled to fit inside a 55-gallon contractor trash bag. The frame breaks down and stores flat against a wall. The entire thing sits neatly in a corner until the next winter. Taking it out of the weather when not in use extends the life of the structure. Since we bought our greenhouse in 2009, pop-up styles have become popular. Like camping tent technology but made with greenhouse materials, this style goes up instantly and collapses flat for storage. Pop-up structures come with stakes and tie-downs to keep them in place. Many are stored in zip bags. An Internet search for “pop-up greenhouse” will turn up many different sizes and styles – from the size of a laundry tote to walk-ins ranging from $30 to more than $300. Rigid cold frame styles also are available. They provide an extra layer of protection on freezing nights to plants that are hardy enough to stand some cold. It’s a cold, unheated greenhouse, so only folks in south Alabama can expect success with the most tender tropical plants. We figure our greenhouse gives us at least 10 degrees of protection, depending on how much sunshine we’ve had.In a vegetable garden, a house without a floor can be placed right on the garden bed to cultivate collards, turnip greens, lettuce and other greens, and to root crops through winter in north and central Alabama. The trick here is to open the doors for ventilation on mild, sunny days so the plants don’t overheat or develop disease problems.Lois Chaplin is an accomplished gardener and author. Her work appears here courtesy of Alabama Farmers Cooperative.