Horticulture Principles and Practices

Cut flowers
Production of cut flowers in the field had been increasing with many of these flowers
destined for local farmer’s markets and roadside markets. During the regular growing
season market growers have an ample supply of cut flowers although the quality can be
negatively impacted by rainfall. As the fall approaches, the numbers of cut flowers
produced begins to decrease rapidly after the first frost. Generally farmer’s markets are
operating long past the first frost so a method of extending the production of cut flowers
would be very important for the producer of field grown cut flowers; however,
information on methods of extending the growing season has been limited. Many
researchers have now demonstrated in the last 3 years that cut flower species can be
successfully grown in high tunnels for approximately 10 months of the year (Figure 8).
GREENHOUSES
Because the cost of glass was prohibitive, greenhouse crop production was not fully
established in the United States until the introduction of polyethylene. The first plastics
were not produced on a commercial scale until 1939. Of these, polyethylene was easy
to manufacture, resistant to chemicals, durable, flexible and relatively free of odor and
toxicity.
In the U.S., the first use of polyethylene as a greenhouse cover occurred in 1948,
when the late Professor Emery Myers Emmert at the University of Kentucky, used the
material in place of glass. Prior to his use of polyethylene, he designed crude wooden
structures over which he placed wooden frames covered with stretched cellophane
supported by wires. In these structures, he grew commercial crops of lettuce, tomato,
cucumber and bedding plants for several years. The first plastic greenhouse was
constructed at the Kentucky Agricultural Experiment Station in 1953 and remained in
use until 1959. Its primary appeal was its comparatively low cost of construction and
maintenance.
Currently, many growers have constructed small to medium size greenhouses
(1,500 to 10,000 square feet) using two layers of greenhouse grade polyethylene film
(6 mil thick) covering the metal frames and inflated with a small blower to provide
stability to the structure under high winds and to increase the insulation value of the
plastic films (Figure 9). These smaller greenhouses are generally heated with propane,
natural gas, #2 fuel oil, wood or in some cases coal. Greenhouses are generally
constructed on a cement or stone base and are considered to be non-movable structures
and taxable. In the last 25 years, construction of multiple-bay greenhouses with plastic
film for their top or roof has been the standard structure for producing horticultural crops
in a large area, 10 to 40 acres. In these large growing structures, the common growing
system is some form of hydroponics (using water as a carrier for nutrients). Crops
FIGURE 8 Snapdragon production
in high tunnel at Penn
State High Tunnel Research and
Education Facility, Rock Springs,
PA. (Photo courtesy of Dr Mike
Orzolek – PSU)
(This item omitted from WebBook edition)
624 Chapter 20 Growing Vegetables Outdoors