One of the first decisions is related to location of the facility. Convenience is obviously a major factor and the proximity to an abundant supply of quality water and electricity. A considerable amount of time will be spent in the greenhouse, so the facility needs to be readily accessible. An adequate water supply is extremely important; for example, to fill a water bed to a depth of 6 inches requires 3.74 gallons per square foot, or for a typical 30 X 100 greenhouse, 11,200 gallons of water are required.
Light is a major factor in plant production. The orientation of the structure will affect light uniformity in the growing area. A north-south orientation is generally best in South Carolina. This orientation minimizes the shading effect of structural members due to the movement of the shaded areas throughout the day.
Shading from outside structures, such as buildings or trees, should be avoided. Wind breaks can be beneficial, but they should not be so close as to shade the greenhouse.
Any number of structures are suitable for growing tobacco transplants. It really depends upon the grower's choice and how they plan to operate the facility. A wood frame structure covered with plastic can do just as good as a steel structure covered with glass.
Several materials are available for covering a greenhouse. A double layer of polyethylene is the most common, due to its durability, low cost, effectiveness, and ease of installation. Glass, acrylic, and polycarbonate provide better light transmission characteristics and are longer lived, but are much more expensive to install.
A double layer of polyethylene is the most common choice for greenhouses in South Carolina. Two layers are used to decrease heat loss through the surface. The outer layer is most often 6 mil, while the inner layer can be either 6 or 4 mil. Most greenhouse films are treated with an ultraviolet light absorber to extend the life of the film for several years. Untreated polyethylene will last only a few months when exposed to sunlight. It is necessary to keep the two layers separated to obtain the insulating benefits of the double layer. Keeping the outside layer taut also minimizes risk of wind damage.
November through January is the time to get the greenhouse ready for the upcoming season. Water analysis should be done at this time. Water should be analyzed on a yearly basis. Sanitize trays if you have not already done so (please see the disease management section for procedures). Inspect the trays for damage and order replacement trays. You may also want to place your media and seed orders at this time. Inspect all greenhouse equipment and perform any needed maintenance. The float bed plastic should be replaced at this time. Fire ants and mice may become a problem as they eat and carry off seed. These pests should be eliminated prior to seeding. In general, get the greenhouse ready to be filled.