The ideal site for a greenhouse is a south to southeast exposure so it can capture all the available light.

As with any structure, a good foundation is crucial, especially where winds are strong. Pour a reinforced concrete footer that extends roughly four inches below grade and four inches above. Use bolts to secure the base plate of the greenhouse to the foundation. For the floor, you can pour a concrete foundation or simply lay down a single sheet of landscape fabric, and cover it with mulch.

One of the most important things to consider when planning a greenhouse is the type of overhead glazing or covering material used. The least expensive is plastic sheeting, but you'll need to replace it every two to three years. Rigid polycarbonate is another choice, and although it lasts a good deal longer than plastic sheeting, it tends to yellow over time. The most durable and expensive of all glazing materials is glass--specifically, tempered glass. No other material captures more light, especially precious winter light.

If the greenhouse will be used year-round, consider your climate. In the northern border states, heat will obviously be required in the cold months, but a cooling device for summer may not be necessary. In the Deep South a greenhouse must be cooled but probably will not have to be heated. In the nation's midsection, both heating and cooling are a must for gardening throughout the year.

Even when the temperature outside is really cold, so long as the sun is shining, the temperature inside the greenhouse can soar. As a matter of fact, for a glass greenhouse, the outside temperature may be 32 degrees and the inside temperature may be close to 100 degrees

For gardeners in all but the most northern climes, controlling temperature during the summer months is essential and usually requires more than one cooling device. Roof vents and shade cloth help reduce inside temperatures; an evaporative cooler does the rest.

To produce strong, healthy plants and reduce their risk of infection from fungal diseases, install a good fan to improve air circulation. A minimum/maximum thermometer is also required.

Benches of various heights will be needed to set plants on. One should be counter height and designated as a potting bench. Some growers prefer wooden benches, but insects can overwinter in the wood, so many gardeners have switched to plastic.

With a greenhouse in place, winter is no deterrent--orchids and other tropicals and warm-season veggies such as tomatoes and peppers are just a step away.