Legend has it that Roman gardeners first invented an early form of greenhouse in order to serve cucumbers at Caesar's table. Whether true or not, the Romans are credited with building the first greenhouses by digging a pit in the earth, adding fires to generate heat, and covering the pit with translucent sheets of mica rock. Ever since, greenhouses, also called glasshouses in Europe, have allowed gardeners the opportunity to grow fruits, vegetables and flowers year-round.
During the 15th century, the explorers who traveled to the New World in search of treasure brought back plant specimens that Europeans had never seen. Many of the roots and berries of these plants were touted as having great curative powers, so the botanists at the time perfected ways to protect and propagate the valued plants in rudimentary greenhouses. By the end of the 16th century, the basic greenhouse was invented, but improvements continued until Victorian England had designed modern greenhouses as we know them today.
While those that worked to perfect the earliest greenhouses imagined plants flourished inside because of the heat generated from fire pits, they were soon to realize that it was actually the light and condensation, or humidity, that was the biggest factor in the growing success of greenhouses.
Today's greenhouses are framed structures enclosed on all sides with acrylic or glass panes. This includes a transparent roof. The clear walls and roof allow in maximum light, trapping warmth. For plants that require partial sun, shade netting or other forms of cover can be erected inside the greenhouse. Greenhouses can be freestanding, or they can be attached to a house or shed in lean-to fashion. There are mini greenhouses with just a few shelves, bay window extensions for growing kitchen herbs, or backyard greenhouses. At the opposite extreme greenhouses can be erected to extend for blocks-on-end for commercial purposes. Whatever plants you want to grow, a greenhouse can be found to help you.
Greenhouses can be purchased prefabricated, in custom-made designs, or as do-it-yourself kits. The structural beams used to support greenhouses can be made of wood, PVC, aluminum or heavier types of metals. Materials used to create the windowpanes can vary from real glass to many types of plastic or synthetic sheeting. If you want to erect a greenhouse with glass panes, it is best to hire a professional installer. The weight of the glass makes it difficult to work with, and the building must be exactly square for proper structural weight distribution.
Just one word of advice for those with green thumbs and dreams of purchasing a greenhouse: Once you see what it can do, you'll probably wish you'd gotten a bigger one.