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The short and dreary days of winter are a test to a gardener's patience. Memories of abundant flowers, vine-ripened tomatoes and other garden delights are often more than some can bear. For those brave, impatient and innovative souls, a greenhouse may provide some relief.

Greenhouses were first built by the Dutch during the 1700s as a way to moderate the long, cold winters in Europe. During the 1800s, greenhouses were considered a trademark of the wealthy. The magnificent structures often produced crops that could not be readily obtained out of season. Extensive transportation systems now allow produce to be shipped from throughout the world to our tables. Greenhouse production of fruits and vegetables is not as indispensable as it was in those times. Greenhouses are no longer the sole province of the wealthy and can now be enjoyed by practically anyone.Many gardeners are interested in building and operating a hobby greenhouse. My co-worker, Jerry Goodspeed, and I are teaching a class to share ideas about greenhouses. The class begins Thursday, Jan. 9. There will an afternoon session from 2 p.m. to 4:30 p.m., or an evening class from 7 p.m. to 9:30 p.m., so choose the time frame that fits your schedule. The cost of the class is $10 and includes a solar greenhouse book and handouts. Call 468-3170 to register.

The class covers many different aspects of greenhouses, including building the structure, greenhouse coverings, heating and cooling, as well as automating some of these menial tasks. Plant propagation, soils, pest control and other relevant topics will also be addressed. It is designed for those gardeners considering building a greenhouse or those who already have a greenhouse and want to know how to utilize it more effectively. Solar design and other energy-saving innovations will also be covered. Hobby greenhouse owners will be teaching some of the sessions and can answer your questions.Greenhouses and other plant-growing structures range from small plastic-covered coldframes to large climate-controlled structures housing full-size trees and landscapes. Time and money are usually the only limitations, but our class is designed to cover small, inexpensive structures.

Many common myths abound about building and operating greenhouses. In reading some recent advertisements, it seems ridiculously easy to grow all the fresh produce a family would want in a very small greenhouse. The produce would be the very highest quality and the cost would be almost nothing, and the extra could feed the neighborhood.

Tomatoes are the most highly promoted and overrated vegetable for greenhouse production. I could name a dozen or more large greenhouse operations that were built to grow tomatoes. All of these were commercial failures. It is simply too costly to heat a greenhouse enough to produce tomatoes and compete with imported vegetables. Even a very small greenhouse may cost $30-100 per month to heat it enough to grow tomatoes. Cool greenhouses are less expensive to operate and can provide much enjoyment. They are kept above freezing, but temperatures are allowed to rise and fall. During the day the sun warms them to a point that a fan may be required to keep them from overheating. These cooler greenhouses keep many plants in good condition and are excellent for starting transplants in the spring.

All greenhouses serve as breeding grounds for pests. Conditions that are right for good plant growth also allow pests to multiply rapidly. Inside the greenhouse they are protected against predators and parasites. Carefully inspect any plants brought into the greenhouse and discard any that are badly infested.

Permanent greenhouses are not cheap. Additions to an existing home may cost thousands of dollars. Considering a greenhouse from an economic standpoint makes it cheaper to buy the transplants rather than make an extensive capital investment. Comparing the cost to a month in a tropical paradise, it may be less expensive to build, equip and maintain a greenhouse. It would at least provide a feeling of warm, growing plants during the bleak days of winter.

Pots on the window, a coldframe in the back yard or a large attached greenhouse all have one thing in common. They provide a "green fix" for gardeners cut off from growing plants. Perhaps building or using one of these structures is appealing to you. Attend the upcoming class and find out.